A patient with early-onset SMAX3 and a novel variant of ATP7A

Abstract

Objective: To describe clinical and genetic studies on a patient with early-onset spinal muscular atrophyX3 (SMAX3) with novel variant of ATP7A.

Methods: Clinical, neurophysiological, neuroimaging and pathological examinations were performed. Whole exome sequencing was applied to search genetic bases of this patient.

Results: The patient had gait abnormality from early infantile period. Muscle imaging at 42 years old showed predominant involvement of proximal muscles as compared to the distal muscles. The patient had a novel variant of ATP7A, which was the fourth genotype of ATP7A exhibited as SMAX3. Contrary to previous reports of distal motor neuropathy, the clinical and neuroimaging findings in this case revealed dominant involvement in the proximal portion of the extremities and trunk, which is similar to patients with type III SMA.

Conclusion: The dominant involvement of proximal motor system in this patient may expand the phenotypic variability of SMAX3. We need to be aware of this disorder in differential diagnosis of patients with type III SMA-like phenotype.

Keywords: ATP7A; Motor neuron disease; SMAX3; Type III SMA.