Attenuated type I mucopolysaccharidosis in the differential diagnosis of juvenile idiopathic arthritis: a series of 13 patients with Scheie syndrome

ABSTRACT Objective. Mucopolysaccharidosis type I (MPS I) is a genetic lysosomal storage disorder caused by deficient activity of the enzyme α-L-iduronidase. Incomplete breakdown of glycosaminoglycans leads to progressive accumulation of these substances in many tissues throughout the body. Patients with the less severe form of MPS I (Scheie syndrome) usually present in the first decade of life with frequent articular involvement, and may survive into adulthood. Especially in these attenuated phenotypes, a definitive diagnosis may be delayed for years because clusters of early symptoms are difficult to recognize for physicians not familiar with the disease, and since the disease progresses slowly over decades. We would like to increase the awareness of this type of MPS I disease among rheumatologists and unravel diagnostic pitfalls. Methods. We have reviewed medical histories of 13 patients (6 males and 7 females) with Scheie syndrome seen in 5 European centers. Results. All patients had prominent musculoskeletal involvement at the onset of their disease in childhood. Diagnosis was delayed in almost all cases (range 4-54 years). Conclusion. We suggest that patients who present with progressive noninflammatory joint involvement in the first decade of life, particularly with stiffness of the fingers and difficulty using the hands, should be screened for metabolic diseases, including MPS I. MPS I should be considered if patients with arthropathy lack the typical characteristics of inflammatory arthropathy.