Trichorrhexis nodosa: An important clue in the diagnosis of citrullinaemia type I

Citrullinaemia type I, a urea cycle disorder due to argininosuccinate synthetase 1 deficiency, can present as either an acute neonatal crisis or a milder, late-onset form. We report a rare presentation of citrullinaemia in a 2-year-old male, where trichorrhexis nodosa served as a clinical clue to the underlying inborn error of metabolism. This case emphasises the need for detailed clinical examination and metabolic workup in cases of unexplained neuroregression and encephalopathy.