Objective: Severe early-onset axonal neuropathy (SEOAN) is a heterogeneous phenotype first delineated by Ouvrier et al., characterized by progressive axonal degeneration with gait problems often progressing to wheelchair requirement and later respiratory involvement. Most cases are sporadic single cases. Some have heterozygous mitofusin 2 (MFN2) mutations, many of which are de novo dominant mutations. The aim of this study was to investigate the mode of inheritance in three individuals with severe early-onset axonal neuropathy and homozygous or compound heterozygous MFN2 mutations.

Methods: The clinical and molecular findings in the parents of three individuals with SEOAN with homozygous or compound heterozygous MFN2 mutations were examined.

Results: All parents were asymptomatic or mildly symptomatic with some signs of peripheral neuropathy indicating a minimal phenotype. Two had hearing problems. All parents carried the relevant single base (heterozygous) MFN2 variations.

Conclusion: Severe early-onset axonal neuropathy due to MFN2 mutations can present as an apparently recessively inherited neuropathy but the minimal phenotype in the parents suggests a semi-dominant mechanism.