Polyneuropathy in the mtDNA base pair 3243 point mutation

To the Editor: Rusanen et al.¹ reported a patient with uniform demyelinating, mixed polyneuropathy (motor more than sensory) who was evaluated as a workup of the family of the clinically definite MELAS and presented with cognitive impairment, hearing impairment, and distal hand and foot weakness with preserved tendon reflexes. Nerve conduction velocity (NCV) studies revealed a reduction in conduction velocity without conduction blocks or temporal dispersion. The uniform nature of demyelination resembled that of the hereditary motor and sensory neuropathies. Several issues can be raised regarding this article.

First, the authors mentioned polyneuropathy in the neuropathy, ataxia, and retinitis pigmentosa (NARP) syndrome and Leigh's syndrome and suggested that both of the phenotypes presented with polyneuropathy of the axonal type. However, in 1986, Goebel et al.² reported demyelinating neuropathy with sural nerve biopsies in four unrelated children in whom the diagnosis of Leigh's disease was verified at autopsy and reviewed 13 previously reported peripheral neuropathy cases in Leigh's disease with the evidence of demyelination in …