Neuropathy due to impaired axonal transport of non-fragmented mitochondria in MYH14 mutation carriers.

With interest we read the article by Almutawa et al. about a family with neuropathy, hypoacusis, and foot deformity, being attributed to the heterozygous variant R941L in MYH14 [1]. Neuropathy was attributed to impaired fission of mitochondria resulting in oversized organelles inappropriate for retrograde axonal transportation [[1], [2]]. We have the following concerns.

A main shortcoming of the study is that no nerve biopsies were carried out. Assuming that neuropathy was due to impaired fission and thus reduced axonal transport of mitochondria [1], it is conceivable that nerve biopsy may show paucity of mitochondria within motor and sensory axons and in nerve terminals. Concerning mitochondrial functions, it is desirable to confirm normal function of the respiratory chain by appropriate biochemical investigations [3].

A further shortcoming is that neuropathy was classified as axonal [1] although there was only borderline CMAP reduction, thus not fulfilling the criteria for axonal degeneration [4]. Additionally, we should know which nerves were involved, if involvement was symmetric/asymmetric, if there was upper/lower limb predominance, and if there was distal, proximal, or diffuse distribution of the lesions. We also should know if motor and sensory nerves were equally affected and if there was involvement of the autonomic fibres.

Missing is an explanation of hypoacusis. We should know if it was due to sensory or neuronal involvement, which could be best achieved by application of acoustically-evoked potentials [5]. We should know why among the cranial nerves only the acoustic nerve was affected and why this cranial nerve was affected long before the onset of peripheral neuropathy.

No funding was received

Author contribution: JF: design, literature search, discussion, first draft, critical comments

Informed consent: was obtained

The study was approved by the institutional review board

Declaration of Competing Interest

None.