Several cases of maternal UPD have been reported. Two phenotypically normal
patients with maternal UPD (isodisomy of 2p and heterodisomy of 2q in one case and two
isochromosomes in the other) appear to exclude the presence of developmentally important imprinted
genes on chromosome 2 (Heide E et al, 2000, Bernasconi F et al, 1996). Other reports
of maternal UPD include patients with congenital abnormalities (Shaffer
LG et al, 1997), congenital hypothyroidism (Bakker et al, 2001), Primary hyperoxaluria
type I (Chevalier-Porst F et al, 2005),
Infantile-onset ascending spastic paralysis (Herzfeld T et al, 2009). A case of maternal UPD
revealed mutations in two separate genes in a 3-year-old Chinese boy with obesity and developmental
delay (Yu T et al, 2016).
Several cases of paternal UPD have been reported. These include cases with Donnai-Barrow syndrome (Kantarci
S et al, 2008)
, Crigler-Najjar type I syndrome (Petit
FM et al, 2005), harlequin icthyosis (Castiglia D et al, 2009), 5alpha-reductase 2
deficiency (Chavez B et al, 2000), and
retinal dystrophy (Thomson DA et al,
2002), 3-hydroxyacyl-CoA dehydrogenase (LCHAD) deficiency (Baskin B et al, 2010).
A phenotypically normal female with complete paternal UPD2 has been reported (Zhang X et al, 2019).
The absence of
clinical features, other than those of the unmasked recessive disorders, suggests that chromosome 2
does not contain developmentally important imprinted genes.