📘 Histidine Disorders · Histidinemia & Urocanic Aciduria

Nelson Textbook of Pediatrics 22nd Ed — Section 105.13. Histidase deficiency (histidinemia) → elevated histidine and urocanic acid. Usually benign, incidental finding on newborn screening. Rarely associated with intellectual disability, speech delay, ataxia. Treatment: low-histidine diet (rarely needed).