A case of transient hyperammonemia in the newborn Transient hyperammonemia of the newborn (THAN) is a rare disease, which occurs most frequently in premature newborn infants. Its aetiology is unknown. After serum ammonia level is normalised, there is no further risk of new episodes of hyperammonemia, and normal intake of proteins is allowed.

The patient was a male newborn of healthy parents, with no consanguinity. The preterm labour occurred in the 30th gestational week, without complication. At admission to NICU the newborn was hypotensive, mechanically ventilated, hypotonic, without spontaneous motoricity. The pupils were nonreactive. Laboratory findings were indicated early neonatal sepsis, acute kidney injury and liver injury. Serum ammonia level was 2181 μmol/l (14.7–134 umol/l). Elevated plasma and urine levels of aminonoacid citrulline were detected. Orotic acid was within the limits of normal. Due to further deterioration of clinical status (therapy ressistent seizures) continuous veno-venous hemodiafiltration (CVVHDF) was innitiated. Serum ammonia gradually started to normalise. The patient was extubated on day 13. After 1.5 months the child was dismissed from hospital. The last check up by physiatrist and neurologist was at four months, and his neurologic development was normal for corrected age.

In conclusion, it is essential to estimate the serum ammonia levels in every preterm newborn infant who develops the signs of RDS, as well as some symptoms of hyperammonemic encephalopathy, in the first hours of life, and to immediately perform therapeutic measures leading to elimination of ammonia from the blood, in order to prevent the brain damage.