KIF5A and ALS: a clinical and genetic description of a case series and review of literature.

Approximately 10% of ALS (amyotrophic lateral sclerosis) cases show a family history, and the remaining 90% are sporadic. In 2018, through genome sequencing using two independent approaches, KIF5A was described as a novel ALS-associated gene. To describe clinical and genetic characteristics of a series of patients with motor neuron disease (MND), diagnosed at University Hospital of Palermo, carrying KIF5A variants. During 2019–2023, two hundred twenty-four patients with MND and healthy subjects with familial history of MND, underwent next-generation sequencing (NGS) for molecular analysis, including genetic testing for C9orf72 hexanucleotide-repeat expansion. The most mutated ALS genes, including KIF5A, were included in a NGS panel. Of the entire tested population, eight patients (including a brother and a sister) were found to carry KIF5A variants. Four patients had familial ALS, the other four were sporadic. Six patients were females (75%). Mean age at ALS onset was 59 years (33–75). Patients were evaluated according to the ALSFRS-revisited during follow-up visits. According to disease progression rate, five patients were defined as ∆FS ≤ 0.5 (slow-progressors), the remaining three patients showed a ∆FS > 1 (fast-progressors). Of the seven KIF5A variants, three are not already described in literature (respectively c.170 C > T, p.Thr57Met; c.2920T > G, p.Ser974Ala and c.2732 A > C, p.Lys911Thr). Two patients showed the association of variations in KIF5A with variations or mutations in other ALS genes, one of them carried a pathogenic variant of FUS (P525L). This study demonstrates phenotypic variability related to mutations in different regions of the same gene resulting in a susceptibility for the disease spectrum with different characteristics.