Alström syndrome caused by maternal uniparental disomy

PURPOSE: To describe a case of Alström syndrome arising from maternal uniparental disomy. OBSERVATIONS: A 13-month-old boy with poor vision and nystagmus was diagnosed with Alström syndrome based on genetic testing that identified a homozygous pathogenic variant, ALMS1 c.2141_2141del (p.Ser714Tyrfs*6), that was only found in his mother and not his father. In contrast to the usual autosomal recessive inheritance pattern in which a child inherits a variant from each parent, multi-step genetic testing of the child and both parents confirmed uniparental disomy as the mechanism of inheritance. CONCLUSIONS AND IMPORTANCE: Confirmation of uniparental disomy in autosomal recessive disorders allows for parental assurance that future offspring will be unaffected.