Localized scleroderma is characterized by idiopathic fibrosis of the skin and adjacent structures, and muscle involvement occurs predominantly in deep morphea. We report a patient with linear scleroderma who presented with slowly progressive atrophy, muscle weakness, and loss of function of her right arm, mimicking a neuromuscular disorder. Muscle biopsy eventually revealed zones of myositis, compatible with morphea profunda. Morphea profunda may thus present as a neuromuscular mimic, even in case of nonprogressive skin sclerosis.
Myositis in morphea profunda is generally limited to one region, whereas inflammatory myopathies generally cause diffuse proximal muscle weakness and atrophy. Furthermore, skin changes in morphea profunda differ from those seen in dermatomyositis, and histological features of muscle biopsy can further distinguish between morphea profunda and inflammatory myopathies. Muscle biopsy in morphea profunda implies the risk of sampling error, whereas results of electromyography and muscle imaging might better represent the extent of muscle inflammation.