Ornithine translocase deficiency, also called hyperornithinemia-hyperammonemia-homocitrullinuria (HHH) syndrome,[1] is a rare autosomal recessive[2] urea cycle disorder affecting the enzyme ornithine translocase, which causes ammonia to accumulate in the blood, a condition called hyperammonemia.

This cycle processes excess nitrogen, generated when protein is used by the body, to make a compound called urea that is excreted by the kidneys.

The SLC25A15 gene provides instructions for making a protein called a mitochondrial ornithine transporter.

This protein is needed to move a molecule called ornithine within the mitochondria (the energy-producing centers in cells).

Specifically, this protein transports ornithine across the inner membrane of mitochondria to the region called the mitochondrial matrix, where it participates in the urea cycle.