In contrast, individuals affected with a severe neurogenic FA sequence with arthrogryposis of multiple joints were recently identified to harbour biallelic loss-of-function (LOF) variants in KIF21A. In addition to the mutational type and functional character such as GOF and LOF and their underlying gene dosage, the resulting phenotype might also depend on the exact position of alterations within the protein and if one or both gene copies are affected. The gene discussed is KIF21A; the disease is Friedreich ataxia.