Renal transplantation in a boy with methylmalonic acidaemia

Guidelines for the diagnosis and management of methylmalonic acidaemia and propionic acidaemia: First revision

Isolated methylmalonic acidaemia (MMA) and propionic acidaemia (PA) are rare inherited metabolic diseases. Six years ago, a detailed evaluation of the available evidence on diagnosis and management of these disorders has been published for the first time. The article received considerable attention, illustrating the importance of an expert panel to evaluate and compile recommendations to guide rare disease patient care. Since that time, a growing body of evidence on transplant outcomes in MMA and PA patients and use of precursor free amino acid mixtures allows for updates of the guidelines. In this article, we aim to incorporate this newly published knowledge and provide a revised version of the guidelines. The analysis was performed by a panel of multidisciplinary health care experts, who followed an updated guideline development methodology (GRADE). Hence, the full body of evidence up until autumn 2019 was re-evaluated, analysed and graded. As a result, 21 updated recommendations were compiled in a more concise paper with a focus on the existing evidence to enable well-informed decisions in the context of MMA and PA patient care.

Post-transplantation Outcomes in Patients with PA or MMA: A Review of the Literature

Introduction

Liver transplantation is recognised as a treatment option for patients with propionic acidemia (PA) and those with methylmalonic acidemia (MMA) without renal impairment. In patients with MMA and moderate-to-severe renal impairment, combined liver–kidney transplantation is indicated. However, clinical experience of these transplantation options in patients with PA and MMA remains limited and fragmented. We undertook an overview of post-transplantation outcomes in patients with PA and MMA using the current available evidence.

Methods

A literature search identified publications on the use of transplantation in patients with PA and MMA. Publications were considered if they presented adequate demographic and outcome data from patients with PA or MMA. Publications that did not report any specific outcomes for patients or provided insufficient data were excluded.

Results

Seventy publications were identified of which 38 were full papers. A total of 373 patients underwent liver/kidney/combined liver–kidney transplantation for PA or MMA. The most typical reason for transplantation was recurrent metabolic decompensation. A total of 27 post-transplant deaths were reported in patients with PA [14.0% (27/194)]. For patients with MMA, 18 post-transplant deaths were reported [11% (18/167)]. A total of 62 complications were reported in 115 patients with PA (54%) with cardiomyopathy (n = 12), hepatic arterial thrombosis (HAT; n = 14) and viral infections (n = 12) being the most commonly reported. A total of 52 complications were reported in 106 patients with MMA (49%) with viral infections (n = 14) and renal failure/impairment (n = 10) being the most commonly reported.

Conclusions

Liver transplantation and combined liver–kidney transplantation appears to benefit some patients with PA or MMA, respectively, but this approach does not provide complete correction of the metabolic defect and some patients remain at risk from disease-related and transplantation-related complications, including death. Thus, all treatment avenues should be exhausted before consideration of organ transplantation and the benefits of this approach must be weighed against the risk of perioperative complications on an individual basis.

Improvement in the prognosis and development of patients with methylmalonic acidemia after living donor liver transplant

Liver transplant is a treatment option for patients with MMA-emia. While this therapy does not bring about a complete cure, it is expected to prolong survival and improve the QOL of patients. The aim of this study was to evaluate the significance of LDLT for patients with MMA-emia in Japan. Clinical information on 13 patients with MMA-emia who underwent LDLT was acquired using a self-developed questionnaire sent to the doctors who provided medical care to patients with MMA-emia after LDLT. Almost all of the patients continued on a protein-restricted diet, and the number of acidosis attacks had significantly decreased. Physical growth had recovered to within the normal range by 2.5 years after LDLT, especially in patients who underwent LDLT before the age of 1 year. The average propionyl carnitine (C3) level had significantly decreased after LDLT, and the DQs had not worsened. Liver transplant should be performed for MMA-emia in early life. This can be expected to maintain neurological development and improve the growth and QOL of patients. However, LDLT is not a curative treatment for MMA-emia. A protein-restricted diet should be continued, and renal function should be monitored closely, with consideration of a renal transplant.

Methylmalonic and propionic acidemias: clinical management update

PURPOSE OF REVIEW

Recent clinical studies and management guidelines for the treatment of the organic acidopathies methylmalonic acidemia (MMA) and propionic acidemia address the scope of interventions to maximize health and quality of life. Unfortunately, these disorders continue to cause significant morbidity and mortality due to acute and chronic systemic and end-organ injury.

RECENT FINDINGS

Dietary management with medical foods has been a mainstay of therapy for decades, yet well controlled patients can manifest growth, development, cardiac, ophthalmological, renal, and neurological complications. Patients with organic acidopathies suffer metabolic brain injury that targets specific regions of the basal ganglia in a distinctive pattern, and these injuries may occur even with optimal management during metabolic stress. Liver transplantation has improved quality of life and metabolic stability, yet transplantation in this population does not entirely prevent brain injury or the development of optic neuropathy and cardiac disease.

SUMMARY

Management guidelines should identify necessary screening for patients with methylmalonic acidemia and propionic acidemia, and improve anticipatory management of progressive end-organ disease. Liver transplantation improves overall metabolic control, but injury to nonregenerative tissues may not be mitigated. Continued use of medical foods in these patients requires prospective studies to demonstrate evidence of benefit in a controlled manner.

Dimethylarginines as biomarkers for the kidney transplant management in methylmalonic aciduria

Methylmalonic aciduria (MMA) is an inborn error of metabolism associated with many complications despite treatment. Chronic renal failure is the most common problem, and patients may eventually require kidney transplant. Therefore, it is worth investigating whether living donor kidney transplant offers a better option than deceased kidney donors; and the value of novel vascular risk biomarkers in the assessment of transplanted MMA patients. We report a case of a 26-year-old man with MMA, who progressed to end-stage renal disease and received kidney transplant from a heterozygous next-of-kin living donor at 20 years of age. Although post-transplant urinary levels of methylmalonic acid decreased, this reduction was lower than previously reported for deceased donors. No episodes of metabolic decompensation were observed after transplantation. During his clinical progress, vascular complications appeared; and finally, pancreatitis was the cause of death. After kidney transplant, we evaluated novel vascular risk factors, such as asymmetric dimethylarginine (ADMA) and symmetric dimethylarginine (SDMA), which were used as early biomarkers of progression and metabolic management for this transplanted patient. This case report illustrates the disadvantage of transplantation with an allograft from a heterozygous living donor, and the utility of vascular risk biomarkers in renal transplant assessment.

A detailed analysis of methylmalonic acid kinetics during hemodialysis and after combined liver/kidney transplantation in a patient with mut (0) methylmalonic acidemia

End stage kidney disease is a well-known complication of methylmalonic acidemia (MMA), and can be treated by dialysis, kidney transplant, or combined kidney-liver transplant. While liver and/or kidney transplantation in MMA may reduce the risk of metabolic crisis and end-organ disease, it does not fully prevent disease-related complications. We performed detailed metabolite and kinetic analyses in a 28-year-old patient with mut (0) MMA who underwent hemodialysis for 6 months prior to receiving a combined liver/kidney transplant. A single hemodialysis session led to a 54 % reduction in plasma methylmalonic acid and yielded a plasma clearance of 103 ml/min and VD0.48 L/kg, which approximates the total body free water space. This was followed by rapid reaccumulation of methylmalonic acid over 24 h to the predialysis concentration in the plasma. Following combined liver/kidney transplantation, the plasma methylmalonic acid was reduced to 3 % of pre-dialysis levels (6,965 ± 1,638 (SD) μmol/L and 234 ± 100 (SD) μmol/L) but remained >850× higher than the upper limit of normal (0.27 ± 0.08 (SD) μmol/L). Despite substantial post-operative metabolic improvement, the patient developed significant neurologic complications including acute worsening of vision in the setting of pre-existing bilateral optic neuropathy, generalized seizures, and a transient, focal leukoencephalopathy. Plasma methylmalonic acid was stable throughout the post-operative course. The biochemical parameters exhibited by this patient further define the whole body metabolism of methylmalonic acid in the setting of dialysis and subsequent combined liver/kidney transplant.

Proposed guidelines for the diagnosis and management of methylmalonic and propionic acidemia

Methylmalonic and propionic acidemia (MMA/PA) are inborn errors of metabolism characterized by accumulation of propionic acid and/or methylmalonic acid due to deficiency of methylmalonyl-CoA mutase (MUT) or propionyl-CoA carboxylase (PCC). MMA has an estimated incidence of ~ 1: 50,000 and PA of ~ 1:100’000 -150,000. Patients present either shortly after birth with acute deterioration, metabolic acidosis and hyperammonemia or later at any age with a more heterogeneous clinical picture, leading to early death or to severe neurological handicap in many survivors. Mental outcome tends to be worse in PA and late complications include chronic kidney disease almost exclusively in MMA and cardiomyopathy mainly in PA. Except for vitamin B₁₂ responsive forms of MMA the outcome remains poor despite the existence of apparently effective therapy with a low protein diet and carnitine. This may be related to under recognition and delayed diagnosis due to nonspecific clinical presentation and insufficient awareness of health care professionals because of disease rarity.

These guidelines aim to provide a trans-European consensus to guide practitioners, set standards of care and to help to raise awareness. To achieve these goals, the guidelines were developed using the SIGN methodology by having professionals on MMA/PA across twelve European countries and the U.S. gather all the existing evidence, score it according to the SIGN evidence level system and make a series of conclusive statements supported by an associated level of evidence. Although the degree of evidence rarely exceeds level C (evidence from non-analytical studies like case reports and series), the guideline should provide a firm and critical basis to guide practice on both acute and chronic presentations, and to address diagnosis, management, monitoring, outcomes, and psychosocial and ethical issues. Furthermore, these guidelines highlight gaps in knowledge that must be filled by future research. We consider that these guidelines will help to harmonize practice, set common standards and spread good practices, with a positive impact on the outcomes of MMA/PA patients.

Combined liver and kidney transplantation in children

Simultaneous combined liver-kidney transplantation (CLKT) is a rare operation in pediatric patients so that annually only 10-30 operations are performed worldwide. The main indications for CLKT are primary hyperoxaluria type 1 and autosomal recessive polycystic kidney disease. In addition, CLKT is indicated in individual patients with metabolic or cirrhotic liver diseases and end-stage kidney disease. The surgery and immediate post-operative management of CLKT remain challenging in infants and small children. The patients should be operated on before they become severely ill or develop major systemic manifestations of their metabolic disorder. The liver allograft is immunologically protective of the kidney graft in simultaneous CLKT, often resulting in well-preserved kidney function. The long-term outcome after CLKT is nowadays comparable to that of isolated liver and kidney transplantations.

Renal transplantation in 4 patients with methylmalonic aciduria: a cell therapy for metabolic disease

INTRODUCTION

Patients with methylmalonic acidemia (MMA) may develop many complications despite medical treatment, in particular, severe central nervous system damage and chronic kidney disease (CKD). A kidney transplant may partially correct the metabolic dysfunctions. Liver, kidney and combined liver-kidney transplantations have been advocated but no guidelines are available to identify the most suitable organ to transplant.

PATIENTS AND METHODS

Four patients with MMA (mut° phenotype) received a kidney graft because of repeated metabolic decompensations, with progression to CKD in 3 patients (end-stage kidney disease in two patients and CKD stage III in one patient with an estimated glomerular filtration rate [eGFR] of 40ml/min/1.73m(2)) but normal renal function in one (eGFR of 93ml/min/1.73m(2)) before transplantation.

RESULTS

The medium age at transplantation was 7.9y (5-10.2) and the median follow-up was 2.8years (1.8-4.6). Renal transplantation improved the relevant metabolic parameters in 4/4 patients and renal function in the patients with CKD. Plasma and urinary MMA levels immediately decreased and remained normal or subnormal (mean values of plasma MMA before transplantation 1530μmol/L versus 240μmol/L after transplantation, and mean values of urine MMA before transplantation 4700mmol/mol creatinine versus 2300mmol/mol creatinine after transplantation). No further acute metabolic decompensation was observed and protein-intake was increased from 0.60 to 0.83g/Kg/day. One patient transplanted at age 9.7years developed a hepatoblastoma at age 11years with subsequent neurological complications and eventually died. The three other patients are alive. Two of them remained neurologically stable. The 3rd patient who displayed choreoathetosis transiently improved his neurological condition immediately after transplantation and then remained stable.

CONCLUSION

Kidney transplantation represents an interesting alternative therapeutic option in methylmalonic aciduria, for renal complications but also as a "cellular therapy" that may significantly reduce metabolic decompensations and hospitalizations. However, further neurological impairment remains possible.

Increased susceptibility of brain acetylcholinesterase activity to methylmalonate in young rats with renal failure

Tissue methylmalonic acid (MMA) accumulation is the biochemical hallmark of methylmalonic acidemia. Clinically, the disease is characterized by progressive neurological deterioration and renal failure, whose pathophysiology is still undefined. In the present study we investigated the effect of acute MMA administration on some important parameters of brain neurotransmission in cerebral cortex of rats, namely Na(+), K(+)-ATPase, ouabain-insensitive ATPases and acetylcholinesterase activities, in the presence or absence of kidney injury induced by gentamicin administration. Initially, thirty-day old Wistar rats received one intraperitoneal injection of saline or gentamicin (70 mg/kg). One hour after, the animals received three consecutive subcutaneous injections of MMA (1.67 μmol/g) or saline, with an 11 h interval between each injection. One hour after the last injection the animals were killed and the cerebral cortex isolated. MMA administration by itself was not able to modify Na(+), K(+)-ATPase, ATPases ouabain-insensitive or acetylcholinesterase activities in cerebral cortex of young rats. In rats receiving gentamicin simultaneously with MMA, it was observed an increase in the activity of acetylcholinesterase activity in cerebral cortex, without any alteration in the activity of the other studied enzymes. Therefore, it may be speculated that cholinergic imbalance may play a role in the pathogenesis of the brain damage. Furthermore, the pathophysiology of tissue damage cannot be exclusively attributed to MMA toxicity, and control of kidney function should be considered as a priority in the management of these patients, specifically during episodes of metabolic decompensation when MMA levels are higher.

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.