Mucopolysaccharidosis Type I in Children, a Forgotten Diagnosis Responsible for Undiagnosed Musculoskeletal Complaints: Report of Two Cases.

Mucopolysaccharidoses (MPS) are a subgroup of lysosomal storage disorders. The underlying mechanism of MPS disorders are deficiency in specific enzymes which leads to accumulation of partially degraded glycosaminoglycans (GAGs) in various tissues. A wide variety of manifestations are reported but musculoskeletal complaints are common among them. In milder forms of MPS, musculoskeletal complaints are presenting symptoms. Delays in diagnosis due to unspecific and mild symptoms is common. Misdiagnosis of MPS as juvenile idiopathic arthritis and other inflammatory arthritis disorders is frequent. Early diagnosis and treatment prevents irreversible cellular damages and is a key factor in efficacy of enzyme replacement therapy. In this study we described two MPS patients with musculoskeletal complaints who were not diagnosed for a period of time. Although musculoskeletal manifestation are common in a variety of clinical conditions, their presence at low ages or co-occurrence of other manifestations (such as cardiac, respiratory, neurologic, etc.) in multiple systems should prompt evaluation of patients for MPS and other metabolic disorders. The rheumatologists' awareness on MPS should be promoted to achieve timely diagnosis and subsequent early treatment.