Neurocognitive assessment and DNA sequencing expand the phenotype and genotype spectrum of Alstrom syndrome

Alstrom syndrome (OMIM#203800) is an ultra-rare autosomal recessive monogenic disease presenting pathogenic variants in ALMS1 (chromosome 2p13). It is characterized by early onset of blindness, hearing loss and systemic comorbidities, with delayed development without cognitive impairment. We aimed to investigate the cognitive functions and describe new pathogenic variants in Alstrom syndrome patients. Nineteen patients (13 adults, 6 children) underwent a thorough clinical, genetic, laboratory, instrumental, and neurocognitive assessment. Six new pathogenic variants in ALMS1 including the first described in exon 6 were identified. Four patients displayed a mild phenotype characterized by slow disease onset or absence of complications, including childhood obesity and association with at least one pathogenic variant in exon 5 or 6. At neurocognitive testing, a significant proportion of patients had deficits in three neurocognitive domains: similarities, phonological memory, and apraxia. In particular, 53% of patients showed difficulties in the auditory working memory test. We found ideomotor and buccofacial apraxia in 74% of patients. Mild phenotype patients performed better on auditory working memory and ideomotor apraxia test than typical phenotype ones (91.9 + 16.3% vs. 41.7 + 34.5% of correct answers, Z = 64.5, p < .01 and 92.5 + 9.6 vs. 61.7 + 26.3, Z = 61, p < .05, respectively). Deficits in auditory working memory, ideomotor, and buccofacial apraxia were found in these patients and fewer neuropsychological deficits were found in the mild phenotype group. Furthermore, in the mild phenotype group, it was found that all pathogenic variants are localized before exon 8.

Automated summary

Alstrom Syndrome is an extremely rare autosomal recessive monogenic disease caused by pathogenic variants in the ALMS1 gene. A study was conducted to investigate cognitive functions in patients with this syndrome, identifying six new pathogenic variants in ALMS1. The research found that patients with a milder phenotype performed better on certain neurocognitive tests compared to those with a typical phenotype, and deficits in auditory working memory and apraxia were common among all patients.