A Novel GBF1 Variant in a Charcot-Marie-Tooth Type 2: Insights from Familial Analysis

Abstract

Background/objectives: Axonal Charcot-Marie-Tooth disease type 2 (CMT2) accounts for 24% of Hereditary Motor/Sensory Peripheral Neuropathies. CMT2 type GG, due to four distinct heterozygous mutations in the Golgi brefeldin A resistant guanine nucleotide exchange factor 1 (GBF1) gene (OMIM 606483), was described in seven cases from four unrelated families with autosomal dominant inheritance. It is characterized by slowly progressive distal muscle weakness and atrophy, primarily affecting the lower limbs. Here, we present two siblings sharing a novel GBF1 variant.

Methods: Patient II.1 (male, 61 years at onset) presented lower limb hypoesthesia and walking difficulty; the examination revealed a postural tremor, a positive Romberg test, and muscle atrophy in the lower limbs and hands. Patient II.2 (his sister, 59 years at onset) had lower limb dysesthesias, hand paresthesia, and lower-limb stiffness. They underwent clinical evaluations, blood tests, and electroneurography. Their father represents a potentially affected individual, although a genetic analysis was not conducted.

Results: All tests for peripheral neuropathies were unremarkable, including metabolic and autoimmune screening. Both showed a mixed demyelinating-axonal sensory-motor neuropathy. Genetic analysis revealed a new heterozygous GBF1 variant of uncertain significance.

Conclusions: Based on autosomal dominant inheritance, as well as clinical and physiological features, a possible novel CMT2GG was diagnosed. Further research, including functional assays and in vitro studies, is necessary to confirm this variant's causal link.

Keywords: Charcot–Marie–Tooth type 2 (CMT2); Golgi brefeldin A resistant guanine nucleotide exchange factor 1 (GBF1); hereditary motor/sensory peripheral neuropathy.

Figure 1

Pedigree of the family. The black-filled symbols represent symptomatic individuals for whom the genetic analysis supported the diagnosis, while the gray-filled symbol represents a potentially affected individual where a genetic analysis was not conducted.