A case report: identification of a novel exon 1 deletion mutation in the GNE gene in a Chinese patient with GNE myopathy.

RATIONALE

GNE myopathy is caused by mutations in the UDP-N-acetylglucosamine-2-epimerase/N-acetylmannosamine kinase(GNE) gene and is clinically characterized by progressive weakness and atrophy of the lower-limb muscles with quadriceps sparing. Nearly all GNE mutations that have been reported thus far in various ethnic populations around the world have been missense or nonsense mutations.

PATIENT CONCERNS

We describe the case of a 32-year-old woman with GNE myopathy. The patient presented with progressive weakness of the lower-limb muscles that had spread to her legs. Her serum creatine kinase level was higher than the normal range. Mild myogenic changes were detected in the tibialis anterior muscles on electromyography, and moderate fatty infiltration was observed in various lower-limb muscles on magnetic resonance imaging. Histopathological examination of a skeletal muscle biopsy specimen revealed variation in muscle fiber size, rimmed vacuoles, and disorganized intermyofibrillar networks. DNA sequencing testing revealed a compound heterozygous mutation consisting of a known mutation (c.620A > T in exon 3) and a novel (exon 1 deletion) mutation.

DIAGNOSES

Taken together, the clinical features, laboratory testing and DNA findings eventually made the diagnosis of GNE myopathy.

INTERVENTIONS AND OUTCOMES

Based on the diagnosis of the GNE myopathy, the patient was administered sialic acid 6 g a day for 1 year, and up to now, her symptoms did not progress further.

LESSONS

We have reported the case of a GNE myopathy patient with compound heterozygous GNE gene mutations. This case expands the genotypic spectrum of GNE myopathy.