Citrullinemia with an Atypical Presentation: Paroxysmal Hypoventilation Attacks

Citrullinemia type 1 (CTLN1) is a rare inherited urea cycle disorder, which resulted from the deficiency of argininosuccinate synthetase enzyme. We presented an infant who was hospitalized because of acute losses of tonus and cyanotic hypoventilation attacks lasting approximately 4–5 min. The physical and neurological examinations were normal. Ammonia level was in the normal range. Citrulline levels increased in both blood and urine. The blood sample was sent to mutation analysis, which showed one novel and one known mutation on ASS1 gene sequencing: a heterozygous novel mutation p.A94V (c.281C>T) and a heterozygous mutation p.W179R (c.535C>T). Urea cycle disorders should be considered in the differential diagnosis of unexplained brief apnea or hypoventilation attacks, even though those symptoms do not lead to hyperammonemia during infancy and childhood as seen in our patient. This is the first case in terms of atypical clinical presentation with a new mutation for CTLN1.