Familial dysautonomia in a non-Jewish girl, with histological evidence of progression in the sural nerve.

A case of typical familial dysautonomia (HSN, type III) in a non-Jewish girl is reported. The number of unmyelinated fibres was found to be reduced and sural nerve biopsy showed evidence of past axonal degeneration. There was also marked endoneurial fibrosis and a lack of the largest myelinated fibres. Signs of histological progression not yet described in the sural nerve and other clinical and morphological features could be explained by different penetrance degrees of the disease.