DYNC1H1-related disorders: A description of four new unrelated patients and a comprehensive review of previously reported variants.

Heterozygous variants in the DYNC1H1 gene have been associated chiefly with intellectual disability (ID), malformations in cortical development (MCD), spinal muscular atrophy (SMA), and Charcot-Marie-Tooth axonal type 20 (CMT), with fewer reports describing other intersecting phenotypes. To better characterize the variable syndromes associated with DYNC1H1, we undertook a detailed analysis of reported patients in the medical literature through June 30, 2019. In sum we identified 200 patients from 143 families harboring 103 different DYNC1H1 variants, and added reports for four unrelated patients identified at our center, three with novel variants. The most common features associated with DYNC1H1 were neuromuscular (NM) disease (largely associated with variants in the stem domain), ID with MCD (largely associated with variants in the motor domain), or a combination of these phenotypes. Despite these trends, exceptions are noted throughout. Overall, DYNC1H1 is associated with variable neurodevelopmental and/or neuromuscular phenotypes that overlap. To avoid confusion DYNC1H1 disorders may be best categorized at this time by more general descriptions rather than phenotype-specific nomenclature such as SMA or CMT. We therefore propose the terms: DYNC1H1-related NM disorder, DYNC1H1-related CNS disorder, and DYNC1H1-related combined disorder. Our single center's experience may be evidence that disease-causing variants in this gene are more prevalent than currently recognized.