Congenital hypomyelinating neuropathy: two patients with long-term follow-up.

The authors report the long-term prospective follow-up of two unrelated females with congenital hypomyelinating neuropathy (CHN) and review previously reported cases. The authors' first patient presented with neonatal hypotonia and extremely slow nerve conduction velocities. Sural nerve biopsy revealed profound hypomyelination, without inflammation or evidence of myelin breakdown. She is now 9 years of age, and her motor function has continued to improve. Follow-up nerve-conduction velocities are unchanged. The authors' second patient presented at 5 months with hypotonia. Nerve-conduction velocities were extremely slow, and sural nerve biopsy revealed severe hypomyelination, with no inflammation or evidence of myelin breakdown. She is now 5 years of age and has also demonstrated improved motor function. Repeated nerve-conduction velocities are unchanged. Both patients have normal cognitive development. Molecular genetic analysis in Patient 2 disclosed a point mutation in the myelin protein zero gene; this same point mutation has been reported in three other patients diagnosed with Dejerine-Sottas syndrome (DSS) but has never been reported in a patient with CHN. Although CHN is a distinct clinical entity, it may share similar genetic features with DSS.