Connexion

GENATLAS PHENOTYPE

last update : 02-06-2020

Symbol	CYB5R3D
Location	22q13.2
Name	methemoglobinemia, with CYB5R3 deficiency
Corresponding gene	CYB5R3
Other symbol(s)	DIA1
Main clinical features	type I : cyanosis, without over sickness, readily controlled with appropriate medical treatment type II : characterized by cyanosis , leading to severe illness with mental retardation, feeding difficulties, failure to thrive, and psychomotor developmental delay in the first months of life (diaphorase deficiency) type III : deficiency of NADH cytochrome b5 reductase in lymphocytes and platelets as well as in erythrocytes, but there was no associated mental retardation
Genetic determination	autosomal recessive
Function/system disorder	hematology
Type	disease

Gene product

Name

diaphorase (NADH), cytochrome b-5 reductase (DIA1)

Mechanism(s)

Gene mutation	Chromosome rearrangement	Effect	Comments

missense			missense mutations in type I, mutation in exon 7
deletion			more often full stops or deletions in type II, a 3bp deletion in exon 9
missense		abnormal protein/loss of function	D239G mutation perturbed substrate binding, causing both decreased specificity for NADH and increased specificity for NADPH

Remark(s)

homozygous exon 5 skipping, a C to T transition introducing a stop codon in exon 8