Insights into the genetic epidemiology of spinal and bulbar muscular atrophy: prevalence estimation and multiple founder haplotypes in the Veneto Italian region

Abstract

Background and purpose: Literature data on spinal and bulbar muscular atrophy (SBMA) epidemiology are limited and restricted to specific populations. The aim of our study was to accurately collect information about SBMA patients living in the Veneto region in Italy to compute reliable epidemiological data. Androgen receptor (AR) lineages were genotyped to evaluate the presence of a founder effect.

Methods: A prevalence survey considering all SBMA patients diagnosed in the Italian Veneto region on 31 January 2018 was carried out. The presence of different haplotypes obtained genotyping 15 polymorphic markers (single nucleotide polymorphisms and short tandem repeats) around the AR gene was evaluated.

Results: Based on 68 patients, the punctual prevalence of the disease on 31 January 2018 was 2.58/100 000 (95% confidence interval 1.65-3.35) in the male population. Five different haplotypes were identified, confirming the existence of multiple founder effects. It was also observed that, within the same haplotype, patients had a similar CAG repeat number (P-value < 0.001).

Conclusions: A reliable estimation of SBMA prevalence in the Italian Veneto region was calculated which does not seem to be affected by a strong founder effect. Moreover, our data suggest that the length of the CAG expansion could be preserved in patients harbouring the same haplotype.

Keywords: AR; SBMA; epidemiology; founder effect; genetic haplotypes.