The expanding clinical and genetic spectrum of alsin-related disorders: the first cohort of Brazilian patients.

There are three types of autosomal recessive disorders involving pathogenic variants in the ALS2 gene (OMIM*606352), infantile ascending hereditary spastic paraplegia (IAHSP), juvenile primary lateral sclerosis (JPLS) and juvenile amyotrophic lateral sclerosis (JALS), which are rare and related to retrograde degeneration of motor neurons. ALS2 pathogenic variants are distributed widely across the entire coding sequence and mostly result in a loss of protein function. Rarely, patients with JALS have been reported with lower motor neuron involvement. Here, we report the first Brazilian cohort (six patients) of JPLS with novel ALS2 pathogenic variants, and we propose an expanding clinical and genetic spectrum of alsin-related disorders. A review of the literature in PubMed from 2001 to September 2020 allowed us to identify 26 publications about the three different phenotypes caused by ALS2 variants (only case reports or families), encompassing 35 nonrelated families. We compiled data (sex, age, age at onset, first symptoms, atypical clinical features, molecular data, and clinical evolution (improvement or death)) from these studies and analyzed them in a general context on the basis of demographic features.