Mutations in several genes can result in a deficiency of complex III activity in mitochondria. Affected patients may demonstrate a number of clinical findings.


Synonym: ubiquinol cytochrome c reductase deficiency


Genes affected: may include BCS1L (chromosome 2q33), UQCRB (chromosome 8q22), UQCRQ (chromosome 5q31)


Inheritance: autosomal recessive


Clinical features - a severe multisystem disorder often present at birth:

(1) lactic acidosis

(2) hypotonia

(3) hypoglycemia

(4) failure to thrive

(5) encephalopathy

(6) hepatopathy, which can progress to liver failure

(7) renal proximal tubulopathy

(8) variable deafness and blindness


Premature death in early childhood is common but some patients may survive longer.


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