AADC deficiency

The L-amino acid decarboxylase (AADC) deficiency describes a severe neurometabolic disease that prevents the normal growth and proper "data transmission" of the brain. 

AADC is involved in the synthesis of serotonin and catecholamines. If there is a deficiency of this enzyme, the L-dopa formed by phenylalanine via tyrosine can not be further converted to dopamine. It is degraded to homovanillic acid (HVA). HVA is a breakdown product of epinephrine and norepinephrine and acts as a neurotransmitter. An excess can lead to neurotransmitter defects that cause severe neurological disorders. 

Other symptoms associated with neurotransmitter disorders include extrapyramidal movement disorders, hyperreflexia, refractory trauma, severe mental retardation, hypotension and oculogyric crises. The inheritance of the metabolic disease is known to be autosomal recessive.