Myopathy of the Proteus syndrome: hypothesis of muscular dysgenesis.

The Proteus syndrome is a congenital disorder of growth regulation affecting tissues of mesodermal and ectodermal origin. It is expressed as hemihypertrophy, hemimegalencephaly, muscular overgrowth, verrucous epidermal nevi, haemangiomas and bony dysplasias. Muscle biopsies were examined at 7 and 10 yr of age from a girl with this disease. Several cytoarchitectural alterations of myofibres, proliferation of sarcolemmal nuclei, and other myopathic changes were demonstrated in regions adjacent to other with normal myofibres; the boundaries did not correspond to fascicular margins. A perinuclear and subsarcolemmal distribution of excessive desmin was also found. It is suggested that this myopathy represents a new category of neuromuscular disease, "muscular dysgenesis", due to faulty paracrine growth factors.