X-Linked Spinal Muscular Atrophy 2 due to a Synonymous Variant in the <b><i>UBA1</i></b> Gene in a Family with Novel Findings from Turkey

Abstract

Spinal muscular atrophy, X-linked 2 (SMAX2) is a rare type of spinal muscular atrophy characterized by muscle weakness, hypotonia, areflexia, myopathic face, tongue fibrillations, contractures, bone fractures, and cryptorchidism. Variants of the <i>UBA1</i> gene lead to SMAX2. The <i>UBA1</i> gene encodes a protein that activates the ubiquitin pathway which is responsible for protein degradation. Here, we describe a family presenting with hypotonia, muscle weakness, areflexia, contractures, weak cry, in association with other anomalies including myopathic face, scoliosis, tongue fibrillations, and cryptorchidism. Molecular analysis in 2 patients revealed a hemizygous pathogenic variant in the <i>UBA1</i> gene (NM_153280.3, NP_695012.1: c.1731C&#x3e;T [p.Asn577Asn]) inherited from their carrier mothers. Our study presents the first patients from Turkey, widening the phenotypic spectrum of SMAX2 by pectus carinatum, medullary sponge kidney, and frontal cyst.