Clinical features associated with maternal uniparental disomy for chromosome 6

Maternal uniparental disomy for chromosome 6 (upd(Cajaiba MM, Witchel S, Madan-Khetarpal S, Hoover J, Hoffner L, Macpherson T, et al. Prenatal diagnosis of trisomy 6 rescue resulting in paternal UPD6 with novel placental findings. Am J Med Genet Part A. 2011;155 A(8):1996-2002.)mat) has been previously reported to cause intrauterine growth restriction (IUGR), but the specific clinical phenotype has not been defined. Based on clinical data from two new cases and patients from the literature, specific phenotypes and mechanisms will be discussed further.

In case 1, a maternal isodisomy mixed with a heterodisomy was found on chromosome 6, including a regional absence of heterozygosity between 6q23.3 and 6q27. In case 2, a homozygous SCUBE3 mutation and upd(Cajaiba MM, Witchel S, Madan-Khetarpal S, Hoover J, Hoffner L, Macpherson T, et al. Prenatal diagnosis of trisomy 6 rescue resulting in paternal UPD6 with novel placental findings. Am J Med Genet Part A. 2011;155 A(8):1996-2002.)mat, involving the 6p21.1-25.1 region were found. Clinical data related to upd(Cajaiba MM, Witchel S, Madan-Khetarpal S, Hoover J, Hoffner L, Macpherson T, et al. Prenatal diagnosis of trisomy 6 rescue resulting in paternal UPD6 with novel placental findings. Am J Med Genet Part A. 2011;155 A(8):1996-2002.)mat were also reviewed. Of all the 21 reported cases with upd(Cajaiba MM, Witchel S, Madan-Khetarpal S, Hoover J, Hoffner L, Macpherson T, et al. Prenatal diagnosis of trisomy 6 rescue resulting in paternal UPD6 with novel placental findings. Am J Med Genet Part A. 2011;155 A(8):1996-2002.)mat (including our 2 cases), 18 (85.7%) presented IUGR.

The phenotypes of the two newly identified patients with upd(Cajaiba MM, Witchel S, Madan-Khetarpal S, Hoover J, Hoffner L, Macpherson T, et al. Prenatal diagnosis of trisomy 6 rescue resulting in paternal UPD6 with novel placental findings. Am J Med Genet Part A. 2011;155 A(8):1996-2002.)mat further suggest that IUGR is associated with upd(Cajaiba MM, Witchel S, Madan-Khetarpal S, Hoover J, Hoffner L, Macpherson T, et al. Prenatal diagnosis of trisomy 6 rescue resulting in paternal UPD6 with novel placental findings. Am J Med Genet Part A. 2011;155 A(8):1996-2002.)mat and case 2 is the first reported upd(Cajaiba MM, Witchel S, Madan-Khetarpal S, Hoover J, Hoffner L, Macpherson T, et al. Prenatal diagnosis of trisomy 6 rescue resulting in paternal UPD6 with novel placental findings. Am J Med Genet Part A. 2011;155 A(8):1996-2002.)mat patient with a homozygous SCUBE3 gene mutation. However, the specific phenotypes involved in upd(Cajaiba MM, Witchel S, Madan-Khetarpal S, Hoover J, Hoffner L, Macpherson T, et al. Prenatal diagnosis of trisomy 6 rescue resulting in paternal UPD6 with novel placental findings. Am J Med Genet Part A. 2011;155 A(8):1996-2002.)mat and the related mechanisms need to be further studied.