[Nemaline congenital myopathy:clinical features and histopathological findings in nine patients]

Nemaline myopathy is a type of congenital myopathy which presents with hypotonia, muscle weakness which is predominantly proximal, lax ligaments, areflexia and skeletal deformities. It is characterized by the presence of intrasarcolemal or intranuclear rods which can be seen with the red color optical microscope using the Gomori technique, and a defect in the Z line of the sarcomere, detected on electron microscopy (EM).

A retrospective study of the cases of nemaline congenital myopathy diagnosed in our hospital between 1984 and 1997. All patients had clinical laboratory analysis (muscle enzymes), and electromyographic and histopathological (muscle biopsy) studies. In 5 cases EM was done.

Nine patients, four males and five females were studied. Diagnosis was made during the first year of life in 7 cases (77.7%), and was characterized by hypotonia, severe areflexia and proximal muscle weakness, whilst the remainder were diagnosed in adolescence when they presented with a juvenile form of the disorder, with muscle weakness, amyotrophy and scoliosis. Muscle biopsy showed nemaline bodies in a variable proportion of fibres. Intranuclear rods were not identified in any case. In the 5 cases in which ultrastructural studies were done, alterations were detected in the Z line of the sarcomere. The immunohistochemical profile of the rods was positive for alphaactin.

There are no clinical features which permit distinction from other forms of congenital myopathy, so muscle biopsy is necessary for diagnosis. There is great phenotype and prognostic variety in this disorder.