Severe early-onset form: neonatal hypotonia, feeding difficulties, respiratory insufficiency, bradycardia and heart failure (cardiomyopathy), epileptic encephalopathy, and antenatal cerebellar hypoplasia. The course is often fatal in infancy.
Intermediate form: developmental delay, epilepsy and stroke-like episodes in childhood.
Later-onset form: slowly progressive cerebellar ataxia, spasticity (sometimes presenting as hereditary spastic paraplegia), dysarthria and variable cognitive involvement; onset in childhood up to adulthood. Epilepsy may occur.
COQ4