Progressive Neurodegeneration in Children: Are We Diagnosing Too Late?

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Welcome and Introduction

Prof. Samuel Groschel: So, hello everyone. Welcome to this webinar. It's my great pleasure to do this webinar together with my two colleague speakers, Serena Gasperini and Nicole Wolf, about progressive neurodegeneration in children. Are we diagnosing too late? It's a really interesting topic. I think it's also a bit provocative because we as physicians, we don't want to hear that we are diagnosing too late.

But the aim is to discuss how can we recognize progressive neurodegeneration in children earlier and to understand clinical consequences of diagnostic delay. And with that, I can continue. Here are some housekeeping notes. Please take no screenshots, et cetera. We will have at the end, you can take your questions. So, yeah, there's enough time. So, during the talk, please note down your questions.

So, at the end, we can answer them. I can introduce Professor Nicole Wolf. She's from the Leukodystrophy Center in Amsterdam. Very happy that you are here, Nicole, to talk about metachromatic leukodystrophy. Dr. Serena Gasperini is a neurometabolic expert from Monza in Italy. And Serena, you will be presenting about mucopolysaccharidoses type 3. And so, the agenda will be we introduce first these two diseases.

These can be a kind of model for new degeneration, for progressive new degeneration in children and how we can diagnose them very early. And after the introduction, first I and after me, Nicole present these aspects in metachromatic leukodystrophy. I think you all know that this genetic disorder, lysosomal storage disorder, based on an enzyme deficiency of the aryl sulfatase A, leading to accumulation of sulfatides, which after normal development of these children, at some point, the development will be abnormal and there will be first symptoms and then there will be progressive neurodegeneration and both motor and cognitive symptoms due to the demyelination in the brain and in the peripheral nervous system.

And depending on the residual enzyme activity, there's early onset forms that have their symptoms early in life, like the late infantile and early juvenile forms, and they deteriorate neurologically very rapidly. And if there's more residual enzyme activity, then you have later onset of symptoms and then more slowly disease progression. This is kind of the clinical cause of metachromatic leukodystrophy.

And of course, we will discuss which are the early signs later and how we can diagnose this earlier. This is especially relevant in metachromatic leukodystrophy because we have treatment options for the early onset form. There's gene therapy based on an autologous stem cell transplantation available and approved. And for the late onset forms, there is an allogeneic hematopoietic stem cell transplantation available.

So there's additional very important reason why we should diagnose early. Now, I hand over to Serena, or I continue actually. So sorry for that, I thought. So at the end, are you actually introducing the disease? The Sanfilippo syndrome, or MPS III, was diagnosed the first time in 1963. Many symptoms are specific of these disorders and peculiar, but other are common to other LSD and lysosomal storage disorders and other neurodegenerative disorders.

So today, with our talk, we have to explain better which are the difference and the importance of early diagnosis and also of the differential diagnosis for us, for the clinician. The symptoms we can expect in Sanfilippo syndrome are progressive mental delay with epilepsy, hypoacousia, sleep disturbance, hepatomegalian behavioural disturbance, but we have a wide spectrum of, a phenotypic spectrum of disorder from severe form with early symptoms, early onset mental retardation and low life expectancy, about 20 years, till attenuated form with only mild mental retardation behavioural symptoms and also late onset symptoms.

And each patient, every patient is quite different from another. So we have to search for other signs, other of the brain for lysosomal storage disorders and later we can explore them in this talk, what we can search for when we have a patient with a mental retardation or with a normal psychomotor milestone and with a regression after 2-3 years of age when there is usually the onset of the severe form of Sanfilippo.

We have to remember that the large spectrum are due to the level of the enzymatic activity in this autosomal... so rare if we can have misdiagnosis. And I give the word to Samuel again. Thank you.

Thank you, Serena. And now we come back to metachromatic leukodystrophy and hopefully the next slide. And the next one, I can't switch forward, why is it a problem if we diagnose late in metachromatic leukodystrophy? Of course, first of all, it's this time around the diagnosis very burdensome for these families or in all of these surveys, the families say diagnostic uncertainty is that the most agonizing experience what they have during that journey, in addition to this sensitive time of the diagnosis itself and the time to cope with this.

So, this is some quite a burden for these families and in addition, the time between the first symptoms and the diagnosis during that time, especially in the early onset forms, there's already deterioration of symptoms. This is especially relevant when we have treatment options, for example, in this survey by Morton et al., in late infantile children, 50% had already completely wheelchair-bound and already required tube fitting at the time of the diagnosis.

And when we talk about treatment and intervention, we want to diagnose early because in all lysosomal storage disorders, we have increasing accumulation of toxic substrates over time and we want to therefore be early with our intervention to stop this progression of the new degeneration even before there are symptoms and also when there are symptoms. And I already mentioned, we have treatment options for MLD, unfortunately, the enzyme replacement trial was not successful and it was stopped because it did not meet its efficacy endpoints.

But for late onset forms, we have hematopoietic stem cell transplantation and for early forms, as I mentioned, the lentiviral autologous stem cell gene therapy. For the late onset forms, we have consistently described, this is the data from Germany but also from other centers, that there is better outcome for the late onset patients when we treat patients early symptomatic, so with less MRI, with better motor function, with better cognitive function in older children.

But we have seen the best outcome when we treat even earlier, before they have symptoms. And a similar situation is also for the gene therapy trial. Only recently, there were long-term follow-up results presented and these children were treated in the first year of life, most of them, before they had symptoms. They were diagnosed because all the siblings were affected and they treated these early onset forms only and they treated it in the pre-symptomatic stage for the late infantile children and the pre-symptomatic stage for the early juvenile form and in the early symptomatic early juvenile form stage.

And you can see also the earlier they are treated and diagnosed, the better the outcome. So also in the early symptomatic patients, the motor outcome is already less well compared to the children diagnosed in the pre-symptomatic stage. And that's the same for the cognitive function. They, compared to the untreated children, they have almost remained almost in the normal range, whereas the children treated with early symptomatic early juvenile form, they also benefited in general, but benefitted less.

So, here is also this pattern of the earlier we diagnosed and treat, the better the outcome for these children. Of course, this will change how we manage the disease, and we need to guide this process and we need to create guidelines. We are doing this, of course, in network, in the MLD initiative, and also in the European Reference Network for Rare Neurological Disorders.

But this involves all stakeholders and a good discussion on how we can move this forward because there is still, although this is very successful up to now, and probably more successful than in other lysosomal storage disorders, but there are still challenges. Maybe we can discuss them also later. Some of them I have listed here. Of course, it's a new situation that we diagnose a disease in the pre-symptomatic stage.

We are used to diagnose patients when they have symptoms, and that comes with challenges. We need to understand this pre-symptomatic stage better. We need to have biomarkers for onset prediction, for example. We need to then also define optimal timing for treatment in this pre-symptomatic stage because, on the one hand, we know the earlier we treat, the better from a biological point of view. But, on the other hand, there is fear of overtreatment. There are risks and side effects of these treatments.

Thank you. And we create, with every newborn screening, patients in waiting, especially when they have their onset later in life. And this comes with a psychological and management burden for these families, and also because of medicalization of asymptomatic individuals. Interestingly, when we ask patients and caregivers in several surveys, this has been reproduced the majority of affected families and patients strongly support newborn screening, even in the absence of available treatments.

This is from our expert perspective interesting, but also important to take into account. Why is that? And I think one aspect is that this diagnostic odyssey and the uncertainty is very burdensome for these families. And also, it empowers parents with reproductive autonomy and family planning choices. Because also they, I think, experience the knowledge as a tool for proactive management of their lives.

So for the future in MLD, I think, just to summarize this a bit challenging field, and I think this is also applicable to other lysosomal storage disorders. We need more robust natural history data, especially also in the pre-symptomatic stage and biomarkers, advanced biomarkers to also evaluate disease activity to better understand these subclinical disease progression. We need also a standardized care for these patients in waiting to develop structured multidisciplinary clinical protocols and dedicated psychological support for these families.

We need to align our frameworks and take also into consideration the patient needs and integrate their experience and priorities in our decision pathways. And we need to manage this transformation now. We manage the disease realistically. We know that newborn screening policy changes and rollouts move slowly, and we will continue to face the reality of diagnosing children too late.

And I think this is a good point to hand over to the next speaker, Nicole Wolf, to learn about to enhance our clinical vigilance and diagnostic pathways. Nicole, thank you.

Metachromatic Leukodystrophy — Prof. Nicole Wolf

Prof. Nicole Wolf: Thank you so much, Samuel, for starting this webinar and explaining the current situation and it's great that newborn screening for metachromatic leukodystrophy is already in place in several countries, at least in pilots, but sometimes as in Norway, already part of the standard neurological, sorry, neonatal screening program. So this will change our patients we see. And I would like to speak of the clinical practice as it's still today in many countries, including the Netherlands.

And I also have some problems moving the slides. Okay, try again. Now, there we should be. So let's look at the practical aspects and situations we encounter in our patients. So, the diagnostic delay is still considerable in patients with MLD, and there are two main reasons. Either you attribute symptoms and signs in a patient to another disease, and I will give some examples, or you think of a possibility of a neurodegenerative disease, but then you ask for non-selective testing as, for example, whole exome screening, and that comes with waiting times.

In our country, if you don't ask for a really fast diagnostic process, for example, in a very sick newborn, you wait for three to six months for a result of a whole exome screening, and that's really too long for our patients. And that delay may mean being too late for treatment. There are some symptoms which we don't consider truly symptomatic, and I will get to that later, and as Professor Gerschl has already shown, symptomatic patient with later onset forms of MLD means considerably less good outcomes for both treatments, allogenic hematopoietic stem cell transplantation, but also gene therapy.

There are opportunities for early diagnosis. Stagnation of motor development, for example, as you saw already in one of the first slides, peripheral polyneuropathy, demyelinating polyneuropathy, which can start years before central nervous system symptoms develop. So in any child with a demyelinating polyneuropathy, think of the possibility of metachromatic leukodystrophy. And then you have the diagnosis of chronic inflammatory demyelinating polyneuropathy, CIDP, in young children, and I think we all know children with this diagnosis who turned out to have metachromatic leukodystrophy.

So this should really be a differential diagnosis for MLD, and in this group of children, you get elevated CSF protein and partial response to IV immunoglobulins, and that seems to confirm your diagnosis of CIDP, but it isn't. So if you have a two or three or four-year-old child with CIDP, think also of metachromatic leukodystrophy, because that's a form of symptom which is still possible to go to treatment.

Then there are cognitive signs, school difficulties out of the blue, of course, cognitive regression. What we've seen several times is the diagnosis of autism in a previously normal child, which should always ring the bell of something neurodegenerative going on. And then children or youth, adolescents with depression, loss of friends, and certainly these kind of psychiatric symptoms are frequent in later-onset metachromatic leukodystrophy, including adults.

But you should keep an open mind that seemingly common problems could be due to a rare disease. And certainly in children, well-adapted children with normal school performance, a change should be taken seriously. You have some less known symptoms, which should also raise a red flag, a sudden onset strabismus in a young child, especially when it comes together with ocular nerve palsy, like nervous six palsy, and gallbladder polyps or gallbladder stones.

Certainly this group of children, when they have only gallbladder involvement, are perfect candidates for treatments with a very good outcome. And this is very important to keep in mind, that you should look for MLD in any child with gallbladder stones, gallbladder polyps. So what's also something we learned in the last eight or nine years, and which we didn't know before, is that your early MRI in early onset MLD is not always typical, and can even be normal in children who have already central nervous system symptoms.

Look at that child, he was 19 months old, he had a normal MRI at that age, but he had already abnormal gait and pyramidal symptoms, pyramidal signs. We can't explain that so well, but we know that in late infantile MLD that's possible. That's another child with a very mild nonspecific abnormalities. The only thing pointing to MLD might be that little elevated T2 signal in the splenium, where we always say the disease starts, and this child had already lost walking without support.

So clear, due to a pyramidal syndrome, not to a peripheral neuropathy. And actually the same is true for this child. So these very mild, non-characteristic MRI abnormalities can actually point, can actually be metachromatic leukodystrophy. And what's also very impressive, this child who had very mild abnormalities, look what happened within four months with the MRI of that child.

You have here the full-blown picture with the extensive MRI abnormalities typical for metachromatic leukodystrophy,... fibers, the tightrope pattern, and most impressively, the confluent T2 hyper-intense signal of almost the entire white matter. So this is impressive, and I think this is also why we are too late in symptomatic children with any treatment, even with the gene therapy. We just can't keep up with the speed of the disease.

So if you think of a neurodegenerative disease, you should refer quickly to an expert center. You should know your referral centers in that case, and don't lose time with the starting non-selective genetic screening, testing, and then waiting several months for results. So I would like to continue with the case study. That was a patient we saw last year, a five-and-a-half-year-old girl with a normal early development, even a very fast language development.

She was a very intelligent little girl. Her motor development was a little slower. She was able to walk without support at age 15 or 16 months, which is still in the normal range, but just not as fast as some other children are. She went at that time to a regular school. There were no issues, and at the age of almost five years, parents noted a tremor of their hands and difficulties, some difficulties with fine motor tasks due to the tremor.

The GP sent the child to a physiotherapist, and it seemed to be stable. There was no other diagnostic workup done. At the age of a little bit more than five years old, there were some mild gait abnormalities parents noted consisting of inversion of the feet. No other problems, normal speech, normal behavior. Teachers at school didn't report anything special.

She had friends and functioned otherwise than normal. Three months later, the child was referred to a child neurologist, and we saw her a little bit after that, and that at neurological examination, we saw a child with a normal behavior, adequate contact, and normal speech. She had a mild intention tremor and had her hands often in fists with a delayed hand opening.

She had an abnormal gait without support, but bilateral foot drop with inversion and mild scissoring. Muscle tone was elevated at the arms with a pronator catch and clearly elevated in the ankles. She had exaggerated muscle tendon reflexes in her legs and a bilateral Babinski response, so a clear pyramidal syndrome. And when we made her MRI, you see again what I just explained to you, typical full-blown MRI abnormalities.

And in the early juvenile symptomatic cases, in contrast to the later infantile cases, you always find these extensive MRI abnormalities once they are symptomatic. And again, you see the tightrope pattern, the sparing of the subcortical fibers. You also see that, for example, in the central splenium here, you have an area of a more normal-looking hypo-intense signal. But when you look at the diffusion-weighted imaging, you see a restricted diffusion in the corpus callosum and also in parts of the white matter, which actually means an even worse progression than you think.

When we do spectroscopy, we see that the usually highest peak, which should be somewhere here, which is the N-acetyl-aspartate peak, is very low in the white matter, and choline is actually elevated in relation to creatine, so the spectroscopy is also very abnormal. And when we look at more results, we did the erosive fatase activity, it was very low.

She was compound heterozygous for two variants, and both were class V in the gene encoding that enzyme, so the diagnosis of symptomatic early juvenile MLD was made. And the question is, is this child eligible for gene therapy? She was still able to walk without support, which is one important criterion. Her total IQ was 82, with a really affected processing speed.

We did some more investigations. We saw a clearly abnormal gallbladder with a thickened wall with polyps. We saw a very elevated neurofilament light in the serum, which was, is normally at that age around 5 picogram per milliliter. We didn't do nerve conduction velocities in that child. IQ of 82 does not qualify any longer for gene therapy. IQ needs to be above 85, and you may think that this is such a small difference, so why don't you go ahead with the gene therapy?

But with the clear pyramidal syndrome and neurological examination, the young age, the MRI with the spectroscopy and the neurofilament light chain protein all predicted rapid progression. So we didn't do treatments, and in less than six months after the diagnosis, the child had lost walking without support, was incontinent, and had developed swallowing problems, and had already gastrostomy and laparoscopic cholecystectomy, and will receive intrathecal baclofen pump shortly.

So that decision was a good decision, a painful decision, but of course you ask yourself what would have happened if the child had been referred with the tremor of the hands, and I'm quite confident that at that time we still would have been able to do the gene therapy. We looked also at the younger sister of that girl, two years old, normal development, normal neurological examination, but she also was affected, pre-symptomatic early juvenile metachromatic leukodystrophy, with already a very, very tiny abnormalities on the MRI in the white including the splenium.

But a normal spectroscopy with a normal NIA peak, slightly elevated neurofilament light, and this girl went through to urgent gene therapy. So I think what you should keep in mind, when children with late infantile MLD are symptomatic, they are too late for treatment, exceptions regarding symptoms are isolated peripheral neuropathy or gallbladder involvement, and children with early juvenile MLD, unfortunately, when they are symptomatic, they are often too late for treatment.

And if they are still eligible for treatment, outcomes are much less good than in pre-symptomatic patients. Newborn screening will be the way to go to diagnose children early enough, and don't forget to screen siblings of your index patient. Thank you.

MPS III (Sanfilippo Syndrome) — Dr. Serena Gasperini

Dr. Serena Gasperini: Thank you, Nicole. And we go back to mucopolysaccharidosis type 3, Sanfilippo syndrome. The accumulation of a paransulfate, especially in the brain, led to a very complex neuropathological pathway that led to neuroinflammation, raxonal degeneration, alteration of the pathway of autophagia, and also peculiar of MPS III disease are the synaptic function alteration that led to a fluctuating symptoms in these progressive neurodegenerative disorders that led to many other alterations due to production of radical oxygen free increase or other neurotransmitters alteration.

So it's very complex to understand and also to treat. There is not a specific therapy for these disorders, but this is a multisystemic disorder like other mucopolysaccharidosis with in this patient progressive... valvulopathy at heart, with pain at the tips, with other symptoms of related to the brain involvement like behavior disorders, dysphagia, nutritional disorders. So there are some specific related disease morbidities and comorbidities like epilepsy, headache, respiratory dysfunction, endocrinic hypertension, dysphagia, and other not related that are supportive of all the chronical neurodegenerative patients.

And we can have an approach for the follow-up and the patient management holistic with a multisystemic and multidynamic approach for... reflux gastroesophageal reflux and also for the respiratory symptoms like excessive cough, disorder, but not so rare as I said, and we have to imagine that this patient, especially in some times of their life, they have some physiological fluctuation of symptoms, on-off, a type on-off, with some neurological involvement, strange neurological involvement, not so usual, meaning autism or ADHD disorder sometimes.

And so I can, I imagine to describe Sanfilippo syndrome, this diagnostic algorithm. Besides a patient with an hyperactivity, with behavioural disturbance and a global psychomotor delay or decline, we have to search for other multisystemic symptoms like clumsiness, low attention capacity, frequent upper airway infections, sleep disturbance that is a typical symptom of Sanfilippo patients, and other dysmorphisms, like facial dysmorphism, like coarse face, like joint stiffness or dysostosis.

Hirsutism is typical of Sanfilippo patients, synophrys is another typical sign, macroglossia, macrocephaly or dolipocephaly, hepatomegaly with often hypertransaminasemia, umbilical hernia. These are symptoms and signs very important to search for in this patient with behavioural disturbance and global psychomotor delay because it's typical of the storage in the lysosomal disorders. In the pediatric age, these are the main symptoms to search for, but in adult age, these symptoms can be attenuated in this form.

So we can expect also to have a mild epilepsy, mild motor delay, mild aggressivity, and autistic tract with acute psychosis onset. And we have to think about to do a urinary glycosaminoglycans. It's a simple exam, but in expert hand, in expert centre, we can search for and exclude these terrible disorders. The newborn screening is not yet available for this MPS III... biomarkers 12 months, at three years and a half, she presented conductive hearing loss with recurrent, very recurrent, many times a month after respiratory infection with odours.

Adenotonsillary hypertrophy, that is another sign typical of MPS III. At four years, speech and motor delay with clumsiness and motor instability and ADHD presentation disorder and the brain MRI cortical and subcortical atrophy. So the differential diagnosis was between neurodegenerative disorders versus lysosomal disorders. EEG was disorganised in the activity and IQ was low, 50. But we arrived only at six years with the attention of a neurologist that searched for an hepatomegal in micro phase with plump lips and oligocephaly in frontal eminence and put the suspicion of the diagnosis of MPS III, that was confirmed.

So I can imagine too that the diagnostic delay is often spread in many patients with mental delay or global psychomotor delay or regression. So we have searched for, we have searched for, these are the European reference network or the European guidelines, the consensus guidelines that are very important for the follow-up and the management of this. a very complex patient, but we have the duty to monitor strictly the brain, especially the seizure expression of the disorders, because this patient must have both convulsive and not convulsive epilepsy, and so we have to treat them correctly, and we need a correct diagnosis of Sanfilippo syndrome to monitor and consider this typical aspect of the disorders.

Another important aspect for an early diagnosis is the anesthesiological problems that these children have, because they are with the cardiopathy or with the macroglossia, with the stenosis of the upper and lower highway, they are terrible for the anesthesia, they are at great risk during surgery, so they have... a correct diagnosis. In this new era, we have access to some therapy for mucopolysaccharidosis type 3, especially some trials.

We tried in the past with intrathecal therapy, enzymatic... CNS, like in... the use of intracerebral ventricle or intranasal enzyme therapy. Then there is a trial in action actually with recruiting patients also with the enzyme fusion protein. transferrin receptor... the enzyme into the brain. gene therapy... the gene editing. And these are other trials. The previous intrathecal trial in 2015 failed, but other trials go by during time.

Intraventricular now is available, the chimeric fusion recombinant enzyme therapy with insulin-like transferrin antibodies. There is a trial with gene therapy and there is also a trial with rosmarinic acid for the action antioxidant and inflammatory and neuroprotective of this substance to decrease especially dopaminergic neurotoxins. There are trials with polyphenols and also with anaquira. In Italy, we recently approved by the health agency AIFA this trial with anaquira.

The Italian protocol, we started in the beginning of this year with anaquira in this patient to reduce the inflammation and we're monitoring with evaluations. In the meantime, I don't have any results, but previously was made a trial in USA with these molecules, with anaquira, with... and sleep because the sleep disturbance, we see that there is the common and terrible impact on the quality of life of this patient and family.

So, we have in these disorders a multidisciplinary approach for a future, we hope, full of new therapeutic options for this patient and we have the duty to do an early diagnosis, to think about this. Condition to do an awareness about pediatricians, about neurologists, for these terrible disorders, with the population screening, with the genomic screening, with the use of machine learning, with diagnostic algorithms. But we have to think about this problem and these terrible disorders, thank you.

Panel Discussion and Audience Questions

Prof. Nicole Wolf: Thank you so much, Serena and Samuel, for your talks. We are, of course, in highly specialized centers where it's always easy to recognize also mild and sometimes uncharacteristic symptoms. But, Samuel, what would you like to advise a general pediatrician to really pay attention to and refer urgently?

Prof. Samuel Groschel: Yes, this is probably any. Yeah, the short answer is any deviation in children from the normal development, if first there is child with normal development and then there is no more further development but stagnation in development, for example, that is in the onset forms, something very important also in the later onset forms, if there's symptoms and they progress, and I think... I think, or with, yeah, an expert center can always help.

And I know, nicole, you also probably get sent a lot of MRIs and this is always possible to, for example, send MRIs, contact expert centers about which diagnostic tests should be done, because I can imagine that there's a lot of rare disorders and a lot of different specialized tests that it's not always easy to select the best.

Prof. Nicole Wolf: Yeah, I think you mentioned an important point. For both diseases- MPS III and metachromatic leukodystrophy- there are urine tests. The problem is that it's not always standard in your metabolic screening- the mucopolysaccharides and the sulfatides- although we changed that. But, Serena, is that standard part of metabolic screening in your hospital or do you have to ask specifically for mucopolysaccharides and sulfatides?

Dr. Serena Gasperini: Thanks, Nicole, it's a great point.

There is not a specific available in all labs to do the glucosaminoglycans in the urine and so the lack of biomarkers that we can send also far away from the hospital is a great point, as is the measure difficult to do: a wide screening, population screening. Sometimes some labs do on dry blood spot, the urine spot can send a broad sample.

But thinking about these disorders is the main thing to do, because we have to call the expert to do this exam- it's very simple, also by the pediatrician or by other, and centralize the samples is the future, because not every lab can do everything, as you say. But we have to think about these disorders and mainly we have not to justify some symptoms like epilepsy, mental retardation, behavioral disturbance or ADHD. but they are only symptoms, not disorders.

We are searching for the causes for the problems. So we have to consider that one test, more one test is better than no one.

Prof. Nicole Wolf: Yeah, I agree.

Yeah, thank you. And I think that probably we also will be able to get genetic results of broad genetic testing faster than it's the case at the moment. So perhaps in two or three years time, we will all send a whole genome screening and get the result back in two weeks. And then we don't have to discuss so much diagnostic delay any longer.

I hope so. I think the problem is even worse in adults where the diagnostic odysseys are often really, can be longer than 10 years. So that's a whole other story. I see that there are the first questions coming up. So the first question is about the girl I presented with the high neurofilament light of 400 and quick deterioration.

And the question is whether we have a threshold NFL value above which we would consider a child essentially ineligible for gene therapy, regardless of other criteria. I think that's, fortunately, we don't see so high NFL levels and a normal child otherwise, or a child with only very, very mild symptoms otherwise, usually NFL spectroscopy and your MRI lesion load and so on go hand in hand. I wouldn't only look at NFL in isolation.

Samuel, what would you say?

Prof. Samuel Groschel: Yes, the same. But we need to learn about that. We need to learn, especially in pre-symptomatic children, what does it tell us together with other factors?

Prof. Nicole Wolf: Yeah, yeah, there is so much to learn. So the next question is for all of us, if a pediatrician suspects something neurodegenerative and sends a whole exome sequencing panel, which can take months, what we discussed, at what point should they be picking up the phone to a specialist rather than wait for the results? Is there a practical rule of thumb?

Serena, would you like to start with that question?

Dr. Serena Gasperini: I may answer immediately because sometimes we have no time, especially for the trial. You say before we have no time And so we are not waiting at all, but have an interaction with the expert center, in my opinion.

Prof. Nicole Wolf: Yeah, Samuel, what are your thoughts?

Prof. Samuel Groschel: Yeah, the same. If you suspect something neurodegenerative, if symptoms progress or some symptoms appear that in a child that was first normally developing. So the pediatrician or neuropediatrician has to make that clinical decision. Is it a child, a normally developing child that suddenly something changes, something even generic that is suspicious of something neurological, then we should not wait. And especially when there's then. Yeah, most more specific progressive symptoms.

Prof. Nicole Wolf: Yeah, yeah, I totally agree with both of you and I would like to remind you that we are- we are all tried neurologists and there could be also other diseases. Then when you're new to generative genetic diseases, one of the first children I saw in Amsterdam was a young girl of two years older with a slowly progressive ataxia and I suspected genetic disease and at the MRI she had a huge pelasitic astrocytoma.

So your MRI is, in my mind, really important. With the cavities that in early, in the late infantile form of MLD you don't necessarily see abnormalities. But you can also have a completely other diagnosis which needs also a fast approach like operation. So don't forget that. So I also would say: send the children and to pick up the phone. I don't see any more questions.

Prof. Samuel Groschel: There's one more question.

Prof. Nicole Wolf: Oh, yes, oh, yes, yes, sorry, yes, yes. What's the current guidance on repeat MRI once MLD is considered the targeted biochemical testing hasn't confirmed the diagnosis? Is there risk that waiting for a second MRI creates the same delay problem you are trying to solve someone? That is a great question for you.

Prof. Samuel Groschel: Yes, I think with the first MRI you can already say a lot, together with the symptoms that you have. So please, before waiting for another MRI, contact an expert center and present the MRI and the symptoms together, because we can, we in. We have knowledge about the natural history and the MRI evolution, as, nicole, you showed and and the pattern is often very clear.

So if there's first symptoms, a specific age range, and and and and and, am I available. That always helps. And if you, in this specific situation where you expect an early infantile MLD and the MRI is still normal, quickly do an urine test of sulfatides, that also helps.

Prof. Nicole Wolf: It's a great point.

Dr. Serena Gasperini: As I say, there's a multisystemic disorder. So we are searching for, beside the autism and ADHD, also other signs. The infection- as I said, in my case, rapper was prevalent in these disorders- the facial dysmorphism. We are searching for epitomegaly and we have a speech delay in this patient. This is typical with the oldest, with the upper eye ways, involvement with the titties.

So we are searching and asking for the patient for these things we are searching for here. So this we have a global, holistic approach to this patient because the face is very important, the confirmation of the cranial with the dolly push, FLE or macro several is typical of this patient. So we have to consider this because the motor impairment is late in time in this patient and we have the more signs beside to behavior disturbance.

So we are such for and we can do an exam, more exam, because I've been obliged cancer in Europe we can do above one year of age every time. So better one exam more than lose this.

Prof. Nicole Wolf: Well, thank you so much, thanks to the audience for the great questions and thanks to all the speakers, and have a good day, take care.

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