Mutations in the FIG4 gene are responsible not only for Charcot-Marie-Tooth (CMT) 4J disease, but also for amyotrophic lateral sclerosis and Parkinson disease. In this article, involving clinicians from the Institut de Myologie, published in November 2023, of the eight patients described,
- six had pure CMT and two had CMT associated with Parkinson disease;
- three had an early onset of the disease with a severe form, two an adolescent onset and a more moderate form; two had first signs in their fourth decade;
- four had electrophysiological conduction block, which in two of them led to treatment with intravenous immunoglobulin, which proved ineffective;
- only one person had a homozygous p.Ile41Thr mutation (and a severe, early-onset form), while the other seven were heterozygous for this mutation;
- two heterozygous individuals had the same mutation but very different phenotypes: one presented a severe early-onset form, while the other had a slow-onset form beginning at the age of 49.
