Disorders of mitochondrial function should be considered in infants or children with symmetric abnormalities of the deep gray matter (including the subthalamic nuclei) or dorsal brain stem. Patients may also have white matter disease, cerebellar atrophy, or increased lactate on MRS
There is not a consensus of the classification of these disorders. The most commonly found functional mitochondrial respiratory chain defects were in
Complex I (32%)
Complexes I, III, and IV (26%)
Complexes III (16%)
Complex II (7%)
A. Myopathy
B. Multisystemic disorder
1. Fatal infantile disorder
2. Leigh syndrome
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
A. Multisystemic disorders
1. GRACILE syndrome (Growth retardation, aminoaciduria, cholestatsis, iron overload, lactic acidosis, early death)
2. Leigh syndrome
B. Myopathy
C. Infantile histiocytoid cardiomyopathy
A. Myopathic forms
B. Multisystemic forms
1. Leigh syndrome
2. Alpers syndrome
A. Multisystemic forms
1. Leigh syndrome
2. NARP (Neuropathy, ataxia, retinitis pigmentosa)
3. Familial bilateral striatal necrosis
4. Fatal infantile multisystemic disease