Mucolipidosis: A mimicker of juvenile idiopathic arthritis

Abstract

Many children visit the rheumatology clinic with joint swelling, pain, stiffness, restriction of movement and are eventually diagnosed with arthritis. However, a small proportion may have an alternative diagnosis. Juvenile idiopathic arthritis (JIA), the most common form of chronic arthritis in children is usually a clinical diagnosis, with no available diagnostic markers. 1 Rarely a few non-inflammatory conditions presenting with joint deformities may mimic the presentation of JIA, resulting in incorrect diagnosis and unnecessary treatment with disease-modifying drugs and immunosuppressive therapy. Since the management and long-term outcome of these conditions is starkly different, it is imperative that these differentials be considered, particularly in atypical cases that lack classical signs of inflammation.We report the case of a 9-year-old boy who presented with progressive deformities and restricted movement of bilateral knee and wrist joints and dysmorphic features. He was later diagnosed with an inborn error of metabolism (mucolipidosis III) based on genetic testing. | C A S E REP ORTA 9-year-old male child presented with complaints of progressive painless joint swelling and deformities of the large joints for the past 6 years. These began with swelling of the bilateral knee joints progressing to genu valgum and progressive involvement of bilateral ankle joints and hands over the last 2.5 years. There was no associated joint pain, tenderness, overlying redness, morning stiffness, migratory involvement, fever or any systemic features of illness.Progressive restriction of physical activity and limited mobility including difficulty in squatting, progressive lordosis and incomplete fisting were noted. He was initially managed conservatively with