A novel homozygous FBXO38 variant causes an early-onset distal hereditary motor neuronopathy type IID

Distal hereditary motor neuronopathies (dHMN) are a genetically heterogeneous group of neuromuscular disorders caused by anterior horn cell degeneration and progressive distal muscle weakness. A heterozygous missense variant in FBXO38 has been previously described in two families affected by autosomal-dominant dHMN. In this paper, we describe a homozygous missense variant in FBXO38 (c.1577G>A; p.(Arg526Gln)) in a young Turkish female, offspring of consanguineous parents, with a congenital mild neuronopathy with idiopathic toe walking, normal sensory examination, and hearing loss. This work is the first to describe a novel homozygous variant and a suggested loss of function mechanism in FBXO38, expanding the dHMN type IID phenotype.