Subsarcolemmal expression of utrophin in neuromuscular disorders: an immunohistochemical study of 80 cases.

The immunohistochemical expression of utrophin in 80 muscle biopsies from patients with dystrophinopathies and other neuromuscular disorders is reported. All biopsy specimens were routinely studied by a battery of 12 histoenzymatic techniques, and immunohistochemistry was performed for spectrin, three domains of dystrophin and two domains of utrophin. Abnormal utrophin expression was observed in all dystrophinopathic muscles compared with normal controls or biopsy samples from several other muscular diseases. Inflammatory myopathies presented abnormal overexpression of utrophin and an abnormal dystrophin immunolabeling pattern. This overexpression of utrophin appears to be directly related to the decrease in dystrophin. We conclude that the study of utrophin is important for the histological interpretation and differential diagnosis of dystrophin-related muscular disorders.