Respiratory chain complexes defects: Complex III deficiency. Co Q- cytochrome reductase.
Incidence
Very rare. 2 forms: adult & infantile. It may be a multisystem disorder (plus myopathy) or only muscle involvement. Never reported in Saudi Arabia.
Clinical Characteristics
Muscle Sx, cramps. Adult form: lactic acidemia, ophtalmoplegia, ptosis, dysphagia, ataxia, weakness, exercise intolerance.. The infantile form: lactic acidosis, myoclonus, seizures from birth on, hypotonia, coma & abnormal eye movements.
Precipitants
Exercise induces lactic acidosis.
Provocation Tests
Exercise.
Diagnostic Procedures
EB-F, EB-muscle.