Correlation of skeletal muscle biopsy with phenotype in the familial macrocephaly syndromes.

The muscle biopsy results from 14 children with macrocephaly and hypotonia/weakness were correlated with clinical findings compatible with any of the autosomal dominant macrocephaly syndromes. Thirteen of the 14 had evidence of lipid storage myopathy, either generalised or focal. All 13 had examinations consistent with either benign familial macrocephaly, Ruvalcaba-Myhre-Smith syndrome, or Bannayan-Zonana syndrome. These results suggest that all three of these disorders may represent phenotypic variability at a single genetic locus.