Complex II (Succinate dehydrogenase) is composed of four subunits all encoded by nuclear DNA. Deficiencies result in Mitochondrial disorders ranging from lethal neonatal disease (brain, heart, muscle, liver, and kidneys) to adult onset isolated cardiac or muscle disease with normal cognition. These patients have a deficiency of Succinate - Coenzyme Q reductase.
Complex II deficiency disorders include
A. Succinate dehydrogenase deficiency
1. Encephalomyopathic form with seizures and ataxia
2. Multisystem infantile form with encephalopathy, cardiomyopathy, and renal failure
3. A cerebellar form with ataxia and cerebellar atrophy
4. Leigh syndrome with growth retardation
5. Isolated myopathic form
On brain/spine imaging patients may have
Increased T2 signal of the substantial nigra and basal ganglia
Leukoencephalopathy with sparing of the sucortical white matter
Abnormal signal in the corpus callosum, ventral pons, medulla, and the gray matter of the spinal cord