Cytochrome b5 reductase (CB5R) deficiency is a recessively inherited autosomal disorder that is either benign (type I) or associated with severe neurological problems (type II). Specific mutations in the CYB5R gene are not exclusive to each type.
Two cyanotic children with developmental delay but with slow progression were investigated for CB5R deficiency. A novel mutation, p.Arg58Pro, was independently detected in both cases.
The clinical variability and severity of the disease reflect the combined effects of impaired function of the 2 mutant enzymes. As illustrated by these 2 cases, inheritance of p.Arg58Pro with either p.Gly76Ser or pLeu188del causes a clinical condition more severe than type I and less severe than the type II cases reported to date.
*Department of Haematology, Belfast City Hospital
∥Haematology Research Group, Centre for Cancer Research and Cell Biology, Queen’s University Belfast, Belfast, Northern Ireland
†Department of Paediatric Haematology
‡Department of Neurology and Murdoch Children’s Research Institute, Royal Children’s Hospital, Melbourne, Vic., Australia
§Department of Paediatric Haematology, Royal Manchester Children’s Hospital, Manchester, UK
The authors declare no conflict of interest.
Reprints: Melanie J. Percy, PhD, FRCPath, Department of Haematology, Belfast City Hospital, Lisburn Road, Belfast BT9 7AB, Northern Ireland (e-mail: firstname.lastname@example.org).
Received July 22, 2011
Accepted March 27, 2012