The characteristic symptoms of<unk>  are at least partially caused by bilateral, focal lesions in the brainstem, basal ganglia, cerebellum, and other regions of the brain. The lesions take on different forms, including areas of demyelination, spongiosis, gliosis, necrosis, and capillary proliferation. Demyelination is the loss of the myelin sheath around the axons of neurons, inhibiting their ability to communicate with other neurons. The brain stem is involved in maintaining basic life functions such as breathing, swallowing, and circulation; the basal ganglia and cerebellum control movement and balance. Damage to these areas therefore results in the major symptoms of<unk> —loss of control over functions controlled by these areas. The lactic acidosis sometimes associated with<unk>  is caused by the buildup of pyruvate, which is unable to be processed in individuals with certain types of oxidative phosphorylation deficiencies. The pyruvate is either converted into alanine via alanine aminotransferase or converted into lactic acid by lactate dehydrogenase; both of these substances can then build up in the body.
Leigh syndrome
Tay–Sachs disease
Maroteaux–Lamy syndrome
Coffin–Siris syndrome
Ohtahara syndrome
Nathalie syndrome
Laurence–Moon syndrome
Kosaki overgrowth syndrome