A Case of Osteogenesis Imperfecta Type II With Additional Balanced Translocation t(1;20)(p13;p11.2)

Osteogenesis imperfect (OI) type II is a genetic disorder of bone characterized by bone fragility, multiple fractures, severe bowing and shortening of long bones, and perinatal death due to respiratory insufficiency. It is mainly caused by mutations in the COL1A1 or COL1A2 genes, inherited in an autosomal dominant manner.

A fetal form of this disorder that included brachydactyly, macrocephaly, frontal bossing, soft calvarium, saddle nose, micrognathia, low set ears, and narrow thoracic cavity is described. A postmortem skeletal survey revealed multiple fractures, unossified skull, and long crumpled bones. The fetal karyotype revealed a balanced translocation t(1;20)(p13;p11.2). DNA sequencing detected a c.3065G > T transversion in exon 42 of the COL1A1 gene, a mutation associated with OI type II.

Although the balanced translocation t(1:20)(p13;p11.2) appears to be incidental in our case, identification of the specific mutation and translocation is important for estimation of genetic risk for another afflicted child.