Increased utilization of single nucleotide polymorphism (SNP) array in clinical practice has led to the recognition of uniparental isodisomy (UPD) that either disrupts imprinting patterns or unmasks autosomal recessive alleles (6).
However, the recurrence risk for CAH arising from UPD of a complete chromosome is considered much smaller owing to the mechanism underlying isodisomy formation.
Rhizomelic chrondrodysplasia punctata type 2 resulting from paternal isodisomy of chromosome 1.
The inheritance of two copies of an identical chromosome is known as isodisomy
, and results in whole chromosome ROH.
However, the presence of the same paternal haploid complement in both cell lines suggests paternal uniparental isodisomy
and involvement of only a single egg and sperm nucleus.
In one patient with classic TIOD, a homozygous deletion in exon 14 appeared to have resulted from partial maternal isodisomy of the short arm of chromosome 2 carrying the defective TPO gene (Bakker et al.
Maternal isodisomy for chromosome 2p causing severe congenital hypothyroidism.
for chromosome 7 is compatible with normal growth and development in a patient with congenital chloride diarrhea.