Characterization of the amyotrophic lateral sclerosis-linked P56S mutation of the VAPB gene in Southern Brazil

Abstract

Objective: Amyotrophic lateral sclerosis (ALS) is a rare worldwide heterogeneous neurodegenerative disease with sporadic and familial (FALS) forms. A rare autosomal dominant subtype of FALS was identified in a Brazilian family, classified as ALS type 8 (ALS8) linked to the VAPB gene. The aim of our study was to analyze a series of ALS8 patients from unrelated families in order to further characterize the disease. Methods: We reviewed only patients with probable or definite ALS according to the Awaji criteria being managed at a single center between 2004 and 2018 and with DNA samples available for genetic analysis. A retrospective analysis of clinical, laboratory, and electrophysiological features was performed, relevant data were recorded and DNA was analyzed to detect VAPB gene mutation. Results: Thirty-one ALS patients were eligible for genetic screening for ALS8 and the mutation was detected in five patients from unrelated families. The mean age of onset was 45 ± 5.3 years for the ALS8 group and 47.6 ± 13.1 years for the non-ALS8 group and the time between symptom onset and last follow-up was longer for ALS8 patients. Three patients in the ALS8 group had tremor (60%), four had pain in affected limb (80%) and all had cramps and abdominal protrusion. Conclusions: This study presents the largest series of ALS8 patients in southern Brazil. Our findings demonstrate several clinical features that may be characteristic of ALS8 and confirm that clinicians should suspect ALS8 when the clinical manifestations include cramps, abdominal protrusion, pain, and tremor.