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Deficiency of cytochrome-b5 reductase

MedGen UID:: 75661
•Concept ID:: C0268193
•: Disease or Syndrome

Synonyms:	Diaphorase deficiency; Methemoglobinemia Due to Deficiency of Methemoglobin Reductase; METHEMOGLOBINEMIA, CONGENITAL, AUTOSOMAL RECESSIVE; NADH cytochrome B5 reductase deficiency; NADH diaphorase deficiency; NADH methemoglobin reductase deficiency
SNOMED CT:	Deficiency of cytochrome-b>5< reductase (124184009); Congenital methemoglobinemia due to NADH-cytochrome b5 reductase 3 deficiency (767497003); Congenital NADH-methemoglobin reductase deficiency (767497003); Cytochrome b5 reductase deficiency (767497003); NADH-methemoglobin reductase deficiency (767497003); Chronic familial methemoglobin reductase deficiency (767497003); Autosomal recessive congenital methemoglobinemia (767497003)

Gene (location): Gene(s) directly associated with this condition or phenotype.	CYB5R3 (22q13.2)

Monarch Initiative:	MONDO:0009606
OMIM®:	250800

Definition

Methemoglobinemia due to NADH-cytochrome b5 reductase deficiency is an autosomal recessive disorder characterized clinically by decreased oxygen carrying capacity of the blood, with resultant cyanosis and hypoxia (review by Percy and Lappin, 2008). There are 2 types of methemoglobin reductase deficiency. In type I, the defect affects the soluble form of the enzyme, is restricted to red blood cells, and causes well-tolerated methemoglobinemia. In type II, the defect affects both the soluble and microsomal forms of the enzyme and is thus generalized, affecting red cells, leukocytes, and all body tissues. Type II methemoglobinemia is associated with mental deficiency and other neurologic symptoms. The neurologic symptoms may be related to the major role played by the cytochrome b5 system in the desaturation of fatty acids (Vives-Corrons et al., 1978; Kaplan et al., 1979). [from OMIM]

Clinical features

From HPO

Growth delay

MedGen UID:: 99124
•Concept ID:: C0456070
•: Pathologic Function

A deficiency or slowing down of growth pre- and postnatally.

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Headache

MedGen UID:: 9149
•Concept ID:: C0018681
•: Sign or Symptom

Cephalgia, or pain sensed in various parts of the head, not confined to the area of distribution of any nerve.

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Opisthotonus

MedGen UID:: 56246
•Concept ID:: C0151818
•: Sign or Symptom

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Global developmental delay

MedGen UID:: 107838
•Concept ID:: C0557874
•: Finding

A delay in the achievement of motor or mental milestones in the domains of development of a child, including motor skills, speech and language, cognitive skills, and social and emotional skills. This term should only be used to describe children younger than five years of age.

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Intellectual disability

MedGen UID:: 811461
•Concept ID:: C3714756
•: Mental or Behavioral Dysfunction

Subnormal intellectual functioning which originates during the developmental period. Intellectual disability, previously referred to as mental retardation, has been defined as an IQ score below 70.

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Methemoglobinemia

MedGen UID:: 6339
•Concept ID:: C0025637
•: Disease or Syndrome

Abnormally increased levels of methemoglobin in the blood. In this form of hemoglobin, there is an oxidized ferric iron (Fe +3) rather than the reduced ferrous form (Fe 2+) that is normally found in hemoglobin. Methemoglobin has a reduced affinity for oxygen, resulting in a reduced ability to release oxygen to tissues.

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Polycythemia

MedGen UID:: 18552
•Concept ID:: C0032461
•: Disease or Syndrome

Polycythemia is diagnosed if the red blood cell count, the hemoglobin level, and the red blood cell volume all exceed the upper limits of normal.

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Hypertonia

MedGen UID:: 10132
•Concept ID:: C0026826
•: Finding

A condition in which there is increased muscle tone so that arms or legs, for example, are stiff and difficult to move.

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Microcephaly

MedGen UID:: 1644158
•Concept ID:: C4551563
•: Finding

Head circumference below 2 standard deviations below the mean for age and gender.

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Exertional dyspnea

MedGen UID:: 68549
•Concept ID:: C0231807
•: Sign or Symptom

Perceived difficulty to breathe that occurs with exercise or exertion and improves with rest.

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Cyanosis

MedGen UID:: 1189
•Concept ID:: C0010520
•: Sign or Symptom

Bluish discoloration of the skin and mucosa due to poor circulation or inadequate oxygenation of arterial or capillary blood.

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Strabismus

MedGen UID:: 21337
•Concept ID:: C0038379
•: Disease or Syndrome

A misalignment of the eyes so that the visual axes deviate from bifoveal fixation. The classification of strabismus may be based on a number of features including the relative position of the eyes, whether the deviation is latent or manifest, intermittent or constant, concomitant or otherwise and according to the age of onset and the relevance of any associated refractive error.

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