A very rare, severe, genetic neurometabolic disorder associated with clinical manifestations related to underproduction of serotonin and dopamine, mainly hypotonia, hypokinesia, ptosis oculogyric crises, and signs of autonomic dysfunction.

An abnormally increased muscular tone that causes fixed abnormal postures. There is a slow, intermittent twisting motion that leads to exaggerated turning and posture of the extremities and trunk.