PROXIMAL RENAL TUBULAR-ACIDOSIS SECONDARY TO FK506 IN PEDIATRIC LIVER-TRANSPLANT PATIENTS

We hereby report our experience with an index case of a pediatric live r transplant patient in whom FK506 administration was associated with the development of proximal renal tubular acidosis (RTA), as well the prevalence of acidosis and renal dysfunction in all pediatric liver tr ansplant patients in our institution followed long term during a 6-yea r period. Data were grouped according to immunosuppressant regime: cyc losporine (CsA) only, FK506 only, or CsA with conversion to FK506. A 2 3-month-old female treated with FK506 after orthotopic liver transplan tation (OLT) performed 15 months earlier presented with a I-wk history of fever, watery diarrhea and metabolic acidosis. Although the acidos is did not improve following correction of her hydration status, admin istration of oral bicarbonate was effective. Discontinuation of this t herapy resulted in acidosis. Since other indirect measurements of rena l tubular function were normal, the patient was judged to have an isol ated proximal RTA. In our group of pediatric liver transplant patients converted from CsA to FK506, FK506 administration was associated with a decline in serum bicarbonate (19+/-1 vs. 16+/-1 mEq/I, p<0.02); nei ther blood urea nitrogen nor serum creatinine differed between the two groups. The number of rejection episodes/patient/month was comparable , allowing clinically relevant comparison of relative drug nephrotoxic ities. We conclude that proximal RTA may be a relatively common treata ble complication of FK506 administration in children.