Liver Transplantation for Propionic Acidemia and Methylmalonic Acidemia: Perioperative Management and Clinical Outcomes.

Propionic acidemia (PA) and methylmalonic acidemia (MMA) comprise the most common organic acidemias and account for profound morbidity in affected individuals. Although liver transplantation (LT) has emerged as a bulk enzyme-replacement strategy to stabilize metabolically fragile patients, it is not a metabolic cure because patients remain at risk for disease-related complications. We retrospectively studied LT and/or liver-kidney transplant in 9 patients with PA or MMA with additional focus on the optimization of metabolic control and management in the perioperative period. Metabolic crises were common before transplant. By implementing a strategy of carbohydrate minimization with gradual but early lipid and protein introduction, lactate levels significantly improved over the perioperative period (P < 0.001). Posttransplant metabolic improvement is demonstrated by improvements in serum glycine levels (for PA; P < 0.001 × 10-14 ), methylmalonic acid levels (for MMA; P < 0.001), and ammonia levels (for PA and MMA; P < 0.001). Dietary restriction remained after transplant. However, no further metabolic crises have occurred. Other disease-specific comorbidities such as renal dysfunction and cardiomyopathy stabilized and improved. In conclusion, transplant can provide a strategy for altering the natural history of PA and MMA providing stability to a rare but metabolically brittle population. Nutritional management is critical to optimize patient outcomes.

Treatment of methylmalonic acidemia by liver or combined liver-kidney transplantation.

OBJECTIVE: To assess biochemical, surgical, and long-term outcomes of liver (LT) or liver-kidney transplantation (LKT) for severe, early-onset methylmalonic acidemia/acid (MMA). STUDY DESIGN: A retrospective chart review (December 1997 to May 2012) of patients with MMA who underwent LT or LKT at Lucile Packard Children's Hospital at Stanford. RESULTS: Fourteen patients underwent LT (n = 6) or LKT (n = 8) at mean age 8.2 years (range 0.8-20.7). Eleven (79%) were diagnosed during the neonatal period, including 6 by newborn screening. All underwent deceased donor transplantation; 12 (86%) received a whole liver graft. Postoperative survival was 100%. At a mean follow-up of 3.25 ± 4.2 years, patient survival was 100%, liver allograft survival 93%, and kidney allograft survival 100%. One patient underwent liver re-transplantation because of hepatic artery thrombosis. After transplantation, there were no episodes of hyperammonemia, acidosis, or metabolic decompensation. The mean serum MMA at the time of transplantation was 1648 ± 1492 µmol/L (normal <0.3, range 99-4420). By 3 days, post-transplantation levels fell on average by 87% (mean 210 ± 154 µmol/L), and at 4 months, they were 83% below pre-transplantation levels (mean 305 ± 108 µmol/L). Developmental delay was present in 12 patients (86%) before transplantation. All patients maintained neurodevelopmental abilities or exhibited improvements in motor skills, learning abilities, and social functioning. CONCLUSIONS: LT or LKT for MMA eradicates episodes of hyperammonemia, results in excellent long-term survival, and suggests stabilization of neurocognitive development. Long-term follow-up is underway to evaluate whether patients who undergo early LT need kidney transplantation later in life.

Long-term correction of urea cycle disorders.

Long-term correction of urea cycle disorders is achieved by correction of the enzymatic defect in hepatocytes. Currently, orthotopic liver transplantation is the primary means of achieving this correction. In the United States most liver transplantations for urea cycle disorders have been restricted to patients with ornithine transcarbamylase deficiency and argininosuccinic aciduria. However, patients with citrullinemia have also received transplants, but more so in Europe and Japan. Recent advances in organ procurement, surgical technique, and immunosuppression have significantly decreased morbidity and mortality. However, unique short-term complications associated with surgery and long-term complications associated with chronic immunosuppression have spurred continued efforts to develop gene replacement therapies for management of acute metabolic decompensations as intercurrent therapy until liver transplantation, and ultimately, for long-term correction. The pathophysiology of urea cycle disorders requires gene vector delivery systems that are highly efficient for liver transduction and transgene expression. To date, adenoviral vectors are unique in fulfilling these criteria, and significant data have been gained in both animal and human studies with early versions of adenoviral vectors. Ultimately, the development of helper-dependent adenoviral vectors may offer the long-term expression and increased margin of safety necessary for adjunctive therapies.

Combined liver-kidney transplantation in methylmalonic acidemia.

A 13-year-old boy with non-B12-responsive methylmalonic acidemia (MMA) had chronic renal failure. Hemodialysis led to symptomatic and biochemical improvement. He subsequently received a combined liver-kidney transplant. After 16 months of follow-up he has a normal lifestyle and a marked reduction in plasma and urine methylmalonate.