Benign methylmalonic acidemia in a sibship with distal renal tubular acidosis

Factors influencing in-hospital death for pediatric patients with isolated methylmalonic acidemia: a nationwide inpatient database analysis

Background

Patients with isolated methylmalonic acidemia (MMA) usually experience recurrent episodes of acute metabolic decompensation or metabolic stroke, require frequent hospitalization, and have a relatively high mortality rate. The aim of our study was to assess factors predicting the in-hospital death of pediatric patients with isolated MMA. We performed a retrospective study using data from the Hospital Quality Monitoring System, a national inpatient database in China collected from 2013 to 2017. All patients under 18 years old with a diagnosis of isolated MMA were included. Demographic, hospital-related, and clinical features were collected. Poisson regression was performed to identify potential influencing variables associated with in-hospital death.

Results

From 2013 to 2017, among 2317 admissions for pediatric patients diagnosed with isolated MMA, 1.77% had the outcome of death. In the univariate analysis, patients aged under 1 year had a higher risk of death than did those aged 1 year or older (odds ratio [OR] = 2.63, 95% confidence interval [CI]: 1.36–5.07). There was a higher risk of in-hospital death for patients admitted through emergency departments or via referrals than for those admitted through other routes (OR = 3.76, 95% CI: 1.84–7.67). Deaths were higher in hospitals with volumes of less than 50 patients with isolated MMA during the five study years (OR = 2.92, 95% CI: 1.46–5.83). Moreover, the risk of in-hospital death gradually decreased over time (OR = 0.72, 95% CI: 0.57–0.90). In the multivariate analysis, the abovementioned associations with the risk of in-hospital death remained statistically significant. However, no significant associations were observed between specific clinical signs and in-hospital death in either the univariate or the multivariate analysis.

Conclusions

Younger age, admission to hospitals with low patient volumes, and admission through emergency departments or referrals are associated with higher risk of in-hospital death. The co-existence of specific clinical signs appears to have no effect on in-hospital death.

Renal dysfunction in methylmalonic acidurias: review for the pediatric nephrologist

Methylmalonic acidurias are a heterogeneous group of inborn errors of branched-chain amino acid metabolism. Depending on the underlying etiology, acute or chronic renal disease constitutes major (long-term) complications. In recent decades, overall survival has improved due to optimized treatment strategies based on the use of standardized emergency protocols and dialysis techniques. The majority of these patients, especially those having mut°, cblB, and cblA deficiency, are at increased risk of developing chronic kidney disease secondary to tubulointerstitial nephritis to require hemo- or peritoneal dialysis. Kidney and/or liver transplantation, as organ replacement, or even gene therapy on a limited scale, are controversially discussed treatment options in methylmalonic acidurias. The pathophysiological basis of renal disease has not been clarified in detail until now, but a severe mitochondrial dysfunction and an impairment of tubular dicarboxylic acid transport due to accumulated toxic metabolic compounds has been recently proposed. Another severe renal complication of methylmalonic acidurias is the occurrence of cblC-associated infantile atypical hemolytic syndrome, which can result in acute kidney injury. Close collaboration between (pediatric) nephrologists and metabolic specialists is required for the long-term management of these patients.