Liver transplantation in propionic acidaemia

Despite the improvement in dietary therapy during the past 20 years, the overall outcome of severe forms of propionic acidaemia (PA) remains often disappointing. Good results can be obtained at a very high price in terms of medical attention, family burden and high cost. In most early onset forms of PA, the intake of natural protein must be rigidly restricted to 8-12 g/day for the first 3 years of life, and then slowly increased to 15-20 g/day by the age of 6-8 years. Supplementation with a precursor-free aminoacid mixture to provide 1.5 g/kg protein per day is generally recommended, although remains controversial. From the age of 1 year onward, these children are often severely anorectic and most of the diet must be delivered by nocturnal gastric drip feeding or gastrostomy. Metronidazole is very effective in reducing the excretion of propionate metabolites derived from the gut. L-carnitine (50 to 100 mg/kg) is systematically given to promote propionylcarnitine synthesis and excretion. We report here a retrospective study of 33 patients with PA diagnosed during the last 20 years in our hospital. Of them, 2 have been liver transplanted. In these two patients who presented frequent severe and unexpected metabolic decompensations despite good compliance with the dietary therapy, orthotopic liver transplantation (OLT) was done at 7 and 9 years respectively. One child died 15 months after transplantation due to a severe lymphoproliferative disorder; the other child now aged 13.5 years is doing well. Despite a persistent methylcitrate excretion, she is under normal moderate daily protein intake (40-50 g/day) and still on carnitine supplementation. Interestingly, another patient who filled the criteria for OLT (very frequent and severe decompensations leading to frequent admissions to the intensive care unit despite excellent dietary management) was also placed on the list for OLT. From the time he was registered onward, he experienced no further episodes of metabolic decompensation, there was almost no interruption in his daily intake and he gained height and weight and developed well. He was finally removed from the list and is still doing very well 2 years thereafter. Correction of propionylCoA carboxylase deficiency restricted to hepatic tissues seems to induce a change towards clinical normalisation and a milder biochemical phenotype. Liver transplanted PA patients still require slight protein restriction and carnitine treatment. We consider that at the moment OLT should only be performed in severe forms of PA, mostly characterised by frequent and unexpected episodes of metabolic decompensation despite good dietary therapy. However, a strict appreciation of these criteria is difficult. A more generalised indication for OLT in PA will require more information about the long-term outcome of transplanted patients. We should also await other alternatives like auxiliary partial OLT from living donors or transplantation of isolated allogenic hepatocytes, genetically modified or not.