Joint Hyperlaxity, Proximal Contractures, and Facial Weakness in Child With Spinal Muscular Atrophy

摘要

To the Editor: Spinal muscular atrophy (SMA) is a disorder of lower motor neurons, which presents with progressive muscle weakness and arefiexia because of mutations in "survival of motor neuron" (SMN) gene. We report uncommon clinical findings in a child with type-2 SMA. A 3-year-old girl presented with stagnation of motor milestones since the age of 6 months. The child had motor stagnation subsequent to learning to sit with support at the age of 6 months. Her language, cognitive development, and social development were normal. On examination, her anthropometry was within normal range. She had velvety hands, neck flexor weakness, facial weakness, hyperlaxity (Fig. 1), and knee and ankle con-tractures. She also had generalized areflexia but no tongue fasciculation. A clinical diagnosis of collagen VI-associated myopathy and SMA were considered. Multiplex ligation-dependent probe amplification analysis of the SMN1 gene showed the deletion of exons 7 and 8, confirming the diagnosis of SMA. Our observation in this child indicates that, SMA should also be considered as a differential in any child with neuromus-cular weakness and hyperlaxity, especially when there is associated areflexia. Neuro-muscular disorders with joint hyperlaxity and contractures include collagen VI-related myopathies, multiminicore diseases, limb girdle dystrophy 2E, Marfan syndrome, Ehlers-Danlos syndrome, and certain types of congenital myopathies (ZAK,P4HA).X Collagen Vl-related myopathies (Ullrich and Bethlem myopathy) are commonly associated with distal hyperlaxity and proximal contractures. A velvety texture of the skin characterized by a zigzag pattern of skin creases has been described in collagen Vl-related myopathy. The areflexia and normal creatine kinase values in the index child lead to a clinical suspicion of SMA.