mitochondrial complex II deficiency

A mitochondrial metabolism disease characterized by a highly variable phenotype. Some patients have multisystem involvement of the brain, heart, muscle, liver, and kidneys resulting in death in infancy, whereas others have only isolated cardiac or muscle invol

A mitochondrial metabolism disease characterized by a highly variable phenotype. Some patients have multisystem involvement of the brain, heart, muscle, liver, and kidneys resulting in death in infancy, whereas others have only isolated cardiac or muscle involvement with onset in adulthood and normal cognition. It has_material_basis_in homozygous or compound heterozygous mutation in the nuclear-encoded SDHA gene on chromosome 5p, the nuclear-encoded SDHAF1 gene on chromosome 19q, or the nuclear-encoded SDHD gene on chromosome 11q23.

Signs and symptoms

• Elevated lactate:pyruvate ratio
• Decreased activity of mitochondrial complex II
• Truncal ataxia
• Developmental regression
• Increased circulating lactate concentration
• Global developmental delay
• Dystonia
• Short stature
• Flexion contracture
• Seizure

Also known as: isolated mitochondrial respiratory chain complex II deficiency; isolated succinate-CoQ reductase deficiency; isolated succinate-coenzyme Q reductase deficiency; isolated succinate-ubiquinone reductase deficiency