HHH syndrome (Hyperammonemia, Hyperornithinemia, Homocitrullinuria) (Hyperammonemia disorder)
Incidence
Rare. Some 30 pts reported. It is a partial defect of ornithine decarboxylase and transport defect into the mitochondria. CPS activity is low. AR inheritance. Never seen in Saudi Arabia.
Clinical Characteristics
Prolonged neonatal jaundice, mental retardation, infantile spasms and intermittent ataxia. Also episodic vomiting, lethargy, irritability may occur. Hypotonia may be seen. Progressive spastic paresis commonly develops during adolescence. After infancy, most patients select their food (low protein diet) avoiding milk and meat.
Precipitants
High protein formula trigger an attack.
Provocation Tests
None, but high protein intake produce elevation of ammonia and ornithine in blood and homocitrullinuria.
Diagnostic Procedures
None specific.