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.