IGHMBP2 and Charcot-Marie-Tooth disease axonal type 2S: SMARD1 and CMT2S are known to be associated with homozygous or compound heterozygous pathogenic variants in IGHMBP2. Immunoglobulin mu-binding protein 2 (IGHMBP2), encoded by IGHMBP2 in chromosome 11, is a ubiquitously expressed helicase in the human body, with the highest expression in the cerebellum (4), which functions to unwind both DNA and RNA duplexes (5).