Syndrome of deltoid and/or gluteal fibrotic contracture: an injection myopathy.

One hundred and fifteen cases of injection myopathy with deltoid and/or gluteal fibrotic contracture were studied, almost all of whom had definite histories of repeated intra-gluteal or intra-deltoid injections. One third had siblings affected by the same fibro-muscular disorders manifested by focal muscle atrophy and limitation of adduction and flexion of the shoulder or hip. Electromyography disclosed myopathic changes of the fibrotic muscles. Muscle biopsy showed marked perimysial and endomysial fibrosis with non-specific degeneration, regenerative changes and, in some cases, partial denervation signs. Under the electron microscope, endomysial and perimysial collagen fibrils lost their normal unimodal diameter distribution and showed a rather broad spectral distribution of diameters suggesting a defective control of collagen formation in this disease entity. Repeated injection injuries and myotoxicity resulting in multifocal myositis are the first trigger of this fibrotic syndrome, and abnormal control of collagen formation could be another important pathogenic factor.