Palmoplantar keratoderma and Charcot-Marie-Tooth disease: combination of two independent genetic diseases? Identification of two point mutations in the MPZ and KRT1 genes by whole-exome sequencing

[Coincidence of hereditary motor and sensory neuropathy type 1A and limb girdle muscular dystrophy type 2A]

A rare case of two neuromuscular disorders in a 29-year-old female is presented: autosomal dominant hereditary motor and sensory neuropathy type 1A (HMSN1A) due to PMP22 duplication and autosomal recessive limb girdle muscular dystrophy type 2A (LGMD2A) produced by CAPN3 common mutation c.550delA and novel c.575C>G (p.Thr192Ser).Walking difficulties appeared in 27 years, the patient had signs of both disorders, more of LGMD, but was not disabled. HMSN1A was inherited from her father whose disease was not recognized earlier.

The spectrum of Charcot-Marie-Tooth disease due to myelin protein zero: An electrodiagnostic, nerve ultrasound and histological study

OBJECTIVE

Nerve ultrasound (US) data on myelin protein zero (MPZ)-related Charcot-Marie-Tooth disease (CMT) are lacking. To offer a comprehensive perspective on MPZ-related CMTs, we combined nerve US with clinics, electrodiagnosis and histopathology.

METHODS

We recruited 36 patients (12 MPZ mutations), and correlated nerve US to clinical, electrodiagnostic measures, and sural nerve biopsy.

RESULTS

According to motor nerve conduction velocity (MNCV) criteria, nine patients were categorized as "demyelinating" CMT1B, 17 as "axonal" CMT2I/J, and 10 as dominant "intermediate" CMTDID. Sural nerve biopsy showed hypertrophic de-remyelinating neuropathy with numerous complex onion bulbs in one patient, de-remyelinating neuropathy with scanty/absent onion bulbs in three, axonal neuropathy in two, mixed demyelinating-axonal neuropathy in five. Electrodiagnosis significantly differed in CMT1B vs. CMT2I/J and CMTDID subgroups. CMT1B had slightly enlarged nerve cross sectional area (CSA) especially at proximal upper-limb (UL) sites. CSA was negatively correlated to UL MNCV and not increased at entrapment sites. Major sural nerve pathological patterns were uncorrelated to UL nerve US and MNCV.

CONCLUSIONS

Sural nerve biopsy confirmed the wide pathological spectrum of MPZ-CMT. UL nerve US identified two major patterns corresponding to the CMT1B and CMT2I/J-CMTDID subgroups.

SIGNIFICANCE

Nerve US phenotype of MPZ-CMT diverged from those in other demyelinating peripheral neuropathies and may have diagnostic value.