Liver Transplantation for Propionic Acidemia: Evidence From a Systematic Review and Meta-analysis.

BACKGROUND: The worldwide experience of liver transplantation (LT) in the treatment of propionic acidemia (PA) remains limited and fragmented. This review aims to provide a comprehensive and quantitative understanding of posttransplant clinical outcomes in PA patients. METHODS: MEDLINE, Embase, and the Cochrane Library databases were searched for studies focusing on PA patients who underwent LT. The pooled estimate rates and 95% confidence intervals (CIs) were calculated using a random-effects model with Freeman-Tukey double arcsine transformation. RESULTS: Twenty-one studies involving 70 individuals were included. The pooled estimate rates were 0.95 (95% CI, 0.80-1.00) for patient survival and 0.91 (95% CI, 0.72-1.00) for allograft survival. The pooled estimate rates were 0.20 (95% CI, 0.05-0.39) for rejection, 0.08 (95% CI, 0.00-0.21) for hepatic artery thrombosis, 0.14 (95% CI, 0.00-0.37) for cytomegalovirus/Epstein-Barr virus infection, and 0.03 (95% CI, 0.00-0.15) for biliary complications. The pooled estimate rates were 0.98 (95% CI, 0.88-1.00) for metabolic stability, 1.00 (95% CI, 0.79-1.00) for reversal of preexisting cardiomyopathy, and 0.97 (95% CI, 0.78-1.00) for improvement of neurodevelopmental delay. A large proportion of patients achieved liberalization of protein intake posttransplant (pooled estimate rate 0.66 [95% CI, 0.35-0.93]). CONCLUSIONS: Despite the risk of transplant-related complications, LT is a viable therapeutic option in PA patients with satisfactory survival rates and clinical outcomes. Given the diversity in neurological assessment methods and the inconsistency in the achievement of dietary protein liberalization across different studies, consensus on neurological evaluation methods and posttransplant protein intake is necessary. Longer-term clinical outcomes of LT for PA warrants further investigation.

Liver and/or kidney transplantation in amino and organic acid-related inborn errors of metabolism: An overview on European data.

BACKGROUND: This study provides a general overview on liver and/or kidney transplantation in patients with an amino and organic acid-related disorder (AOA) with the aim to investigate patient characteristics and global outcome in Europe. This study was an initiative of the E-IMD and the AOA subnetwork of MetabERN. METHODS: A questionnaire was sent to all clinically active European Society for the Study of Inborn Errors of Metabolism (SSIEM) members. The questionnaire focused on transplanted individuals with methylmalonic acidemia (MMA), propionic acidemia (PA), maple syrup urine disease (MSUD), and urea-cycle disorders (UCDs). RESULTS: We identified 280 transplanted AOA patients (liver transplantation in 20 MMA, 37 PA, 47 MSUD, and 111 UCD patients, kidney or combined liver and kidney transplantation in 57 MMA patients and undefined transplantation type in 8 MMA patients), followed by 51 metabolic centers. At a median follow-up of 3.5 years, posttransplant survival ranged between 78% and 100%, being the lowest in PA patients. Overall, the risk of mortality was highest within 14 days posttransplantation. Neurological complications were mainly reported in Mut0 type MMA (n = 8). Nonneurological complications occurred in MMA (n = 28), PA (n = 7), and UCD (n = 14) patients, while it was virtually absent in MSUD patients. Only 116/280 patients were psychologically tested. In all, except MSUD patients, the intelligence quotient (IQ) remained unchanged in the majority (76/94, 81%). Forty-one percentage (9/22) of MSUD patient showed improved IQ. CONCLUSION: The survival in AOA individuals receiving liver and/or kidney transplantation seems satisfactory. Evidence-based guidelines, systematic data collection, and improved cooperation between transplantation centers and European Reference Networks are indispensable to improve patient care and outcomes.

Liver transplantation in propionic and methylmalonic acidemia: A single center study with literature review.

BACKGROUND: Organic acidemias, especially propionic acidemia (PA) and methylmalonic acidemia (MMA), may manifest clinically within the first few hours to days of life. The classic presentation in the newborn period includes metabolic acidosis, hyperlactatemia, and hyperammonemia that is precipitated by unrestricted protein intake. Implementation of newborn screening to diagnose and initiate early treatment has facilitated a reduction in neonatal mortality and improved survival. Despite early diagnosis and appropriate management, these individuals are prone to have recurrent episodes of metabolic acidosis and hyperammonemia resulting in frequent hospitalizations. Liver transplantation (LT) has been proposed as a treatment modality to reduce metabolic decompensations which are not controlled by medical management. Published reports on the outcome of LT show heterogeneous results regarding clinical and biochemical features in the post transplantation period. As a result, we evaluated the outcomes of LT in our institution and compared it to the previously published data. STUDY DESIGN/METHODS: We performed a retrospective chart review of nine individuals with PA or MMA who underwent LT and two individuals with MMA who underwent LT and kidney transplantation (KT). Data including number of hospitalizations, laboratory measures, cardiac and neurological outcomes, dietary protein intake, and growth parameters were collected. RESULTS: The median age of transplantation for subjects with MMA was 7.2 years with a median follow up of 4.3 years. The median age of transplantation for subjects with PA was 1.9 years with a median follow up of 5.4 years. The survival rate at 1 year and 5 years post-LT was 100%. Most of our subjects did not have any episodes of hyperammonemia or pancreatitis post-LT. There was significant reduction in plasma glycine post-LT. One subject developed mild elevation in ammonia post-LT on an unrestricted protein diet, suggesting that protein restriction may be indicated even after LT. CONCLUSION: In a large single center study of LT in MMA and PA, we show that LT may reduce the incidence of metabolic decompensation. Moreover, our data suggest that LT may be associated with reduced number of hospitalizations and improved linear growth in individuals with PA and MMA.

Methylmalonic acidemia/propionic acidemia - the biochemical presentation and comparing the outcome between liver transplantation versus non-liver transplantation groups.

BACKGROUND: Most patients with isolated methylmalonic acidemia (MMA) /propionic acidemia (PA) presenting during the neonatal period with acute metabolic distress are at risk for death and significant neurodevelopmental disability. The nationwide newborn screening for MMA/PA has been in place in Taiwan from January, 2000 and data was collected until December, 2016. RESULTS: During the study period, 3,155,263 newborns were screened. The overall incidence of MMA mutase type cases was 1/121,356 (n = 26), 1 cobalamin B was detected and that for PA cases (n = 4) was 1/788,816. The time of referral is 8.8 days for MMA patients, and 7.5 days for PA patients. The MMA mutase type patients have higher AST, ALT, and NH3 values as well as a lower pH value (p < 0.05). The mean age for liver transplantation (LT) is 402 days (range from 0.6-6.7 yr) with 16 out of 20 cases (80.0%) using living donors. The mean admission length shortened from 90.6 days/year (pre-LT) to 5.3 days/year (at 3rd year post-LT) (p < 0.0005). Similarly, the tube feeding ratio decreased from 67.8 to 0.50% (p < 0.00005). The anxiety level of the caregiver was reduced from 33.4 to 27.2 after LT (p = 0.001) and the DQ/IQ performance of the patients was improved after LT from 50 to 60.1 (p = 0.07). CONCLUSION: MMA/PA patients with LT do survive and have reduced admission time, reduced tube feeding and the caregiver is less anxious.

Cost-effectiveness of liver transplantation in methylmalonic and propionic acidemias.

Propionic acidemia (PA) and classical methylmalonic acidemia (MMA) are rare inborn errors of metabolism that can cause early mortality and significant morbidity. The mainstay of disease management is lifelong protein restriction. As an alternative, liver transplantation (LT) may improve survival, quality of life, and prevent further neurological deterioration. The aim of our study was to estimate the incremental costs and outcomes of LT versus nutritional support in patients with early-onset MMA or PA. We constructed a Markov model to simulate and compare life expectancies, quality-adjusted life years (QALYs), and lifetime direct and indirect costs for a cohort of newborns with MMA or PA who could either receive LT or be maintained on conventional nutritional support. We conducted a series of 1-way and probabilistic sensitivity analyses. In the base case, LT on average resulted in 1.5 more life years lived, 7.9 more QALYs, and a savings of $582,369 for lifetime societal cost per individual compared to nutritional support. LT remained more effective and less costly in all 1-way sensitivity analyses. In the probabilistic sensitivity analysis, LT was cost-effective at the $100,000/QALY threshold in more than 90% of the simulations and cost-saving in over half of the simulations. LT is likely a dominant treatment strategy compared to nutritional support in newborns with classical MMA or PA.

Clinical characteristics and mutation analysis of propionic acidemia in Thailand.

BACKGROUND: Propionic acidemia (PA) is caused by a deficiency of propionyl CoA carboxylase. A characteristic urine organic acid profile includes 3-hydroxypropionate, methylcitrate, tiglylglycine, and propionylglycine. The diagnosis of PA is confirmed by detection of mutations in the PCCA or PCCB genes. We herein report the clinical and molecular findings of four Thai patients with PA. METHODS: Clinical findings of four Thai patients with PA were retrospectively reviewed. Urine organic acids were analyzed by gas chromatography-mass spectrometry. PCR-sequencing analyses of encoding exons and intron/exon boundaries of the PCCA and PCCB genes were performed. RESULTS: All patients had neonatal onset of PA. One patient died of cardiomyopathy, and another one of pneumonia and metabolic decompensation. The remainder experienced significant neurocognitive impairment. Mutation analysis of the PCCA gene identified homozygous c.1284+1G>A in patient 1, c.230G>A (p.R77Q) and c.1855C>T (p.R619X) in patient 2, homozygous c.2125T>C (p.S709P) in patient 3, and only one mutant allele, c.231+1G>T in patient 4. No PCCB mutation was identified. Four mutations including c.230G>A, c.231+1G>T, c.1855C>T, and c.2125T>C have not been reported previously. CONCLUSIONS: The clinical and molecular study of these Thai patients provided additional knowledge of the genotype and phenotype characteristics of PA. The results of the study suggested that PCCA mutations in Asian populations were distinct from those of other populations.

Clinical features and management of organic acidemias in Japan.

Organic acidemias (OAs) are rare inborn errors of metabolism. The clinical presentations of methylmalonic acidemia (MMA) and propionic acidemia (PA) in Japan have not yet been examined in detail. We aimed to investigate the clinical presentations of OAs in Japan and evaluate current therapies for improving long-term outcomes, especially in MMA and PA cases. Questionnaires were sent to 928 institutions in 2009 inquiring about OAs, and secondary questionnaires were sent to those who confirmed that they had diagnosed and/or treated such cases; 119 cases were eventually included for analysis. In Japan, the majority of OAs was MMA, which was associated with a high mortality rate. The survival rates at 20 years of age in vitamin B12-unresponsive MMA, vitamin B12-responsive MMA and PA patients were 69.8%, 94.4% and 95.8%, respectively. Factors associated with mortality in MMA were failure to thrive, hypoglycemia and pancreatitis. Factors associated with mental retardation in vitamin B12-unresponsive MMA, vitamin B12-responsive MMA, and PA were seizure and liver dysfunction, seizure and failure to thrive, and failure to thrive, respectively. We advocated that avoiding failure to thrive due to too restricted protein diet, hypoglycemia and pancreatitis associated with mortality lead to improve outcome, especially in vitamin B12-unresponsive MMA patients.

The molecular landscape of propionic acidemia and methylmalonic aciduria in Latin America.

In this work, we review the clinical and genetic data in 14 Latin American propionic acidemia (PA) and 15 methylmalonic aciduria (MMAuria) patients. In the PA patients, we have identified four different changes in the PCCA gene, including one novel one (c.414+5G>A) affecting the splicing process. The PCCB mutational spectrum included two prevalent changes accounting for close to 60% of the mutant alleles studied and one novel change (c.494G>C) which by functional analysis is clearly pathogenic. We have also identified the deep intronic change c.654+462A>G, and the results of the antisense treatment in the patient's cell line confirmed the functional recovery of PCC activity. All PA patients bearing out-of-frame mutations presented the disease earlier while patients bearing in hemizygous fashion p.E168K and p.R165W presented the disease later. Regarding the MMAuria patients, we have found three novel mutations in the MUT gene (c.1068G>A, c.1587_1594del8 and c.593delA) and one in the MMAB gene (c.349-1 G>C). Two patients with MMAuria with homocystinuria cblC type are carriers of the frequent c.271dupA mutation. All mut(0), cblB and cblC patients presented the symptoms early and in general had more neurological complications, while cblA and mut(-) patients exhibited a late-onset presentation, and in general the long-term outcome was better. The results presented in this work emphasize the importance of the genetic analysis of the patients not only for diagnostic purposes but also to research into novel therapies based on the genotype.

Short-term rescue of neonatal lethality in a mouse model of propionic acidemia by gene therapy.

Propionic acidemia (PA) is a metabolic disorder that causes mental retardation and that can be fatal if untreated. PA is inherited in an autosomal recessive fashion involving mutations in PCCA or PCCB encoding the alpha and beta subunits of propionyl-CoA carboxylase (PCC). Current treatment is based on dietary restriction of substrate amino acids, which attenuates symptoms. However, patients still experience episodes of hyperammonemia that can cause progressive neurologic damage. In this paper, we have tested gene therapy approaches to PA in a stringent mouse model of PCCA deficiency, in which homozygous knockout mice are born but die within 36 hr. In this work, we have delivered first-generation and helper-dependent adenovirus serotype 5 (Ad5) vectors expressing the human PCCA cDNA by intraperitoneal injection into newborn mice. Unmodified Ad5 vectors mediated extensive transduction of the peritoneum with weak liver transduction as determined by luciferase imaging and dsRed expression. In contrast, modification of Ad5 with polyethylene glycol detargeted the virus from the peritoneum and retargeted it for transduction in the liver. When vectors expressing PCCA were injected, significant increases in life span were observed for both the unmodified and polyethylene glycol (PEG)-modified Ad5 vectors. However, this rescue was transient. Similarly, adeno-associated virus serotype 8-mediated transduction also produced only transient rescue. These data show first proof of principle for gene therapy of PA and demonstrate the potential utility of PEG to modify viral tropism in an actual gene therapy application.