Autosomal recessive axonal neuropathy with neuromyotonia: a rare entity.

BACKGROUND: Autosomal recessive axonal neuropathy with neuromyotonia is a recently described entity associated to the HINT1 gene, encoding histidine triad nucleotide-binding protein 1. PATIENT: The authors report a Portuguese 16-year-old girl of Roma ethnicity, descendant of consanguineous parents, with progressive distal muscular atrophy and weakness, beginning at age 6. After several years of extensive investigation with inconclusive results, clinical myotonia was identified. Electrophysiologic studies revealed neuromyotonia associated with a severe chronic predominantly motor axonal neuropathy and homozygous mutation (c.334 C > A, p.H112 N) in HINT1 was detected.
CONCLUSION: This report emphasizes the late onset of clinical myotonia essential to the diagnosis.