Idiopathic hyperammonemia after solid organ transplantation: Primarily a lung problem? A single-center experience and systematic review.

BACKGROUND: Idiopathic hyperammonemia syndrome (IHS) is an uncommon, often deadly complication of solid organ transplantation. IHS cases in solid organ transplantation seem to occur predominantly in lung transplant (LTx) recipients. However, to the best of our knowledge, the occurrence of IHS has not been systematically evaluated. We set out to identify all reported cases of IHS following nonliver solid organ transplantations.

METHODS: Retrospective review of our institutional experience and systematic review of the literature.

RESULTS: At our institution six cases (of 844 nonliver solid organ transplants) of IHS were identified: five occurred following LTx (incidence 3.9% [lung] vs 0.1% [nonlung], P=.004). In the systematic review, 16 studies met inclusion criteria, reporting on 32 cases of IHS. The majority of IHS cases in the literature (81%) were LTx-recipients. The average peak reported ammonia level was 1039 μmol/L occurring on average 14.7 days post-transplant. Mortality in previously reported IHS cases was 69%. A single-center experience suggested that, in addition to standard treatment for hyperammonemia, early initiation of high intensity hemodialysis to remove ammonia was associated with increased survival. In the systematic review, mortality was 40% (four of 10) with intermittent hemodialysis, 75% (nine of 12) with continuous veno-venous hemodialysis, and 100% in six subjects that did not receive renal replacement to remove ammonia. Three reports identified infection with urease producing organisms as a possible etiology of IHS.

CONCLUSION: IHS is a rare but often fatal complication that primarily affects lung transplant recipients within the first 30 days.