Citrullinemia Type I (CTLN1) is a rare disorder associated with a defect in the urea cycle.

The mutations affect the third step in the urea cycle (generation of arginosuccinic acid from arginine and citrulline).


Inheritance: autosomal recessive


Clinical syndromes:

(1) acute neonatal form

(2) late-onset form

(3) pregnancy-related hyperammonemia


Features of the acute neonatal (classic) form:

(1) apparently normal at birth

(2) progressive lethargy

(3) poor feeding and vomiting

(4) signs of increased intracranial pressure with spasticity, ankle clonus and epilepsy

(5) coma and death if untreated

(6) hyperammonemia


Laboratory findings:

(1) plasma ammonia > 150 µmol/L

(2) plasma citrulline > 1,000 µmol/L

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