A second pedigree with autosomal dominant nemaline myopathy caused by TPM3 mutation: A clinical and pathological study

The slow α-tropomyosin (TPM3) gene has to date been associated with few cases of both dominant and recessive nemaline myopathies. We report the identification of a p.Arg167His mutation in a four-generation family presenting with a mild classical form of the disease. Clinically, there was no correlation between the age at presentation and the severity of the disease. The dominant-negative p.Arg167His mutation is a recurrent mutation, previously reported in one sporadic case. Histological studies showed discrepancy between the two reports. While a type II fibre predominance was described in the sporadic case, we observed an almost complete type I fibre predominance. This study emphasizes the variability in histopathological phenotypes seen with TPM3 mutations.