Figure 1: Clinical and laboratory investigations in the patient.

(a) The patient has a severe distal and proximal weakness affecting the hands and feet and she is wheelchair-bound. (b) Sanger sequencing detected the homozygous c.695A>G, p.(Lys232Arg) mutation in the patient, while both parents were heterozygous carriers of this mutation, and the healthy sister was wild type. (c) Muscle histology showed some groups of atrophic fibers and groups of hypertrophic fibers, typically seen in spinal muscular atrophy. ATPase pH 4.2 staining demonstrates a significant type grouping, in support of the neurogenic atrophy. (d) HE, COX, SDH, COX/SDH. COX is generally weak across the section, also detected in the sequential assay. COX, cytochrome c oxidase; HE, hematoxylin and eosin; SDH, succinate dehydrogenase.