Maternal uniparental isodisomy causing autosomal recessive GM1 gangliosidosis: a clinical report.

[gm1 gangliosidosis]

Uniparental disomy is a genetic cause of disease that may result in the inheritance of an autosomal recessive condition . A child with developmental delay and hypotonia was seen and found to have severely abnormal myelination . Lysosomal enzyme testing identified an isolated deficiency of beta -galactosidase . Subsequently , homozygous missense mutations in the galactosidase , beta 1 (GLB 1 ) gene on chromosome 3 were found . Parental testing confirmed inheritance of two copies of the same mutated maternal GLB 1 gene , and no paternal copy . SNP analysis was also done to confirm paternity . The patient was ultimately diagnosed with autosomal recessive GM 1 gangliosidosis caused by maternal uniparental isodisomy . We provide a review of this patient and others in which uniparental disomy (UPD ) of a non-imprinted chromosome unexpectedly caused an autosomal recessive condition . This is the first case of GM 1 gangliosidosis reported in the literature to have been caused by UPD . It is important for genetic counselors and other health care providers to be aware of the possibility of autosomal recessive disease caused by UPD . UPD as a cause of autosomal recessive disease drastically changes the recurrence risk for families , and discussions surrounding UPD can be complex . Working with families to understand UPD when it occurs requires a secure and trusting counselor -family relationship .