Histidinemia, also known as histidine ammonia-lyase deficiency, is related to phenylketonuria and tyrosinemia. An important gene associated with Histidinemia is HAL (Histidine Ammonia-Lyase), and among its related pathways/superpathways are Metabolism and Regulation of expression of SLITs and ROBOs. Affiliated tissues include skin and cortex, and related phenotypes are histidinuria and hyperhistidinemia