Nemaline (actin) myopathy with myofibrillar dysgenesis and abnormal ossification.

We report a 2-year-old boy who presented with marked hypotonia and was dependent on artificial ventilation since birth. He was diagnosed with nemaline (actin) myopathy, based on the cytoplasmic accumulation of thin filament aggregates and marked myofibrillar dysgenesis. Intranuclear rods and dispersed tiny nemaline bodies were also observed. The patient was shown to be heterozygous for a de novo mutation, c.430C>T (p.Leu144Phe), in the alpha-actin (ACTA1) gene. He also showed orbital osteosclerosis, longitudinal striations of the iliac bones, hepatomegaly, undescended testis, a unilateral vesico-ureteric stenosis, severe failure to thrive, and dilatation of the lateral cerebral ventricles. Besides the severe muscle involvement, these clinical findings further broaden the clinical spectrum of actinopathy phenotypes.