Mucopolysaccharidoses : Misdiagnosis Of Rheumatic Conditions

Dr. Kampuis opens with the case of a young girl with a persistently swollen wrist, eventually diagnosed with mucolipidosis type II/III after years of inconclusive evaluations. The child had a history of trigger finger, general joint stiffness without pain, and minimal systemic symptoms—features often misattributed to JIA. What ultimately led to the correct diagnosis were subtle radiological signs and targeted enzyme testing.

She emphasizes four key red flags that should prompt pediatricians to suspect an underlying metabolic disorder rather than classic JIA:

1. Widespread joint stiffness more than pain.
2. Absence of morning stiffness, which is typical in JIA.
3. History of early trigger fingers or carpal tunnel syndrome.
4. Characteristic skeletal abnormalities on X-rays—particularly “dysostosis multiplex.”

Dr. Kampuis highlights that normal psychomotor development or lack of facial dysmorphism does not exclude LSDs, especially in early stages. She shares visual examples of atypical skeletal changes that may be overlooked unless actively sought. Radiologists may miss these unless specifically prompted to consider metabolic bone disease.

She discusses the diagnostic limitations of general metabolic screening tests (e.g., urine GAGs), advocating instead for specific enzyme assays and genetic testing tailored to clinical suspicion. A key resource recommended is a practical diagnostic guide that compares lysosomal disorders and helps map symptoms to appropriate tests.

The second half of the presentation introduces a case of CACP syndrome (Camptodactyly-Arthropathy-Coxa Vara-Pericarditis), a rare inherited disorder that can also mimic JIA. The case illustrates how family history, consanguinity, and subtle phenotypic clues can direct diagnosis toward a genetic rather than inflammatory origin.

Dr. Kampuis concludes by urging pediatricians and rheumatologists to consider metabolic and genetic disorders early—especially in children with atypical JIA features. Early recognition avoids inappropriate treatments like methotrexate or biologics and enables timely supportive interventions such as physical therapy and genetic counseling.

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