Safety and efficacy of liver transplantation for methylmalonic acidemia: A systematic review and meta-analysis

Background-objectives: Liver transplantation (LT) and combined liver and kidney transplantation (CLKT) have been proposed as enzyme replacement therapies for methylmalonic aciduria (MMA). We aimed to synthesize the available evidence on their safety and efficacy. Methods: Medline, Embase and Cochrane library were searched to identify studies that reported post-LT/CLKT clinical outcomes of MMA from their inception to February 1, 2020. The pooled rate was calculated using random-effects model with Freeman–Tukey double arcsine transformation method. Results: Thirty-two studies involving 109 patients were included. The pooled estimate rates were 99.9% (95% CI 95.3–100.0) for patient survival, 98.5% (95% CI 91.5–100.0) for graft survival after LT/CLKT. The combined incidence of biliary, vascular complications and rejection were 0.2% (95% CI 0.0–6.6), 7.7% (95% CI 0.1–22.1) and 18.4% (95% CI 4.6–36.3), respectively. The pooled estimate rates were 100.0% (95% CI 99.4–100.0) for metabolic eradication, 61.5% (95% CI: 33.4–87.0) for normalization of kidney function. Chronic kidney disease (CKD) remission is more promising after CLKT (70.3% VS 37.6% in LT group). The pooled estimate rates for neurodevelopmental status improvement and protein intake liberalization were 52.0% (95% CI 2.8–98.8) and 36.3% (95% CI 6.3–71.7), respectively. Conclusions: This first quantitative systematic review confirms favorable survival outcomes and partially improved disease-related complications in transplanted MMA patients, although some results should be interpreted with caution. Future studies with detailed description of long-term outcomes and consensus on neurodevelopmental evaluation method can help provide a more accurate picture.