Renal transplantation in a patient with methylmalonic acidaemia

Acute fatal ventricular arrhythmia induced by severe hyperkalemia in a toddler with decompensated methylmalonic acidemia

BACKGROUND

Methylmalonic acidemia is a very rare genetic metabolic disease. Patients with isolated methylmalonic acidemia typically present with acute alterations of consciousness, failure to thrive, anorexia, vomiting, respiratory distress, and muscular hypotonia. Despite the evidence-based management, affected individuals experience significant morbidity and mortality. Hyperkalemia is one of the unusual complications of methylmalonic acidemia.

CASE PRESENTATION

In this paper, we describe a 4-year-old Persian boy with methylmalonic acidemia who developed life-threatening arrhythmia following severe hyperkalemia and metabolic acidosis. Emergent management of the condition was successfully carried out, and the rhythm changed to normal sinus rhythm by effectively reducing the serum potassium level. We discuss the possible etiology of this lethal condition and describe its management on the basis of the available evidence.

CONCLUSION

During metabolic decompensation in methylmalonic acidemia, frequent blood gas and electrolyte testing to prescribe and adjust therapy and annual echocardiogram and electrocardiogram screening are essential.

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.

Kidney disease and organ transplantation in methylmalonic acidaemia

OBJECTIVES

MMA is associated with chronic tubulointerstitial nephritis and a progressive decline in GFR. Optimal management of these children is uncertain. Our objectives were to document the pre-, peri-, and post-transplant course of all children with MMA who underwent liver or combined liver-kidney transplant in our centers.

DESIGN AND METHODS

Retrospective chart review of all cases of MMA who underwent organ transplantation over the last 10 years.

RESULTS

Five children with MMA underwent liver transplant (4/5) and combined liver-kidney transplant (1/5). Three were Mut⁰ and two had a cobalamin B disorder. Four of five were transplanted between ages 3 and 5 years. Renal dysfunction prior to transplant was seen in 2/5 patients. Post-transplant (one liver transplant and one combined transplant) renal function improved slightly when using creatinine-based GFR formula. We noticed in 2 patients a big discrepancy between creatinine- and cystatin C-based GFR calculations. One patient with no renal disease developed renal failure post-liver transplantation. Serum MMA levels have decreased in all to <300 μmol/L. Four patients remain on low protein diet, carnitine, coenzyme Q, and vitamin E post-transplant.

CONCLUSIONS

MMA is a complex metabolic disorder. Renal disease can continue to progress post-liver transplant and close follow-up is warranted. More research is needed to clarify best screening GFR method in patients with MMA. Whether liver transplant alone, continued protein restriction, or the addition of antioxidants post-transplant can halt the progression of renal disease remains unclear.

Hepatoblastoma in a patient with methylmalonic aciduria

Childhood malignant tumors and their treatment are not well described in the natural history of methylmalonic aciduria (MMA). Here we present a case of hepatoblastoma occurring in the native liver of a 19-month-old male with MMA. His tumor was unresectable at diagnosis and he received neoadjuvant chemotherapy with cisplatin, 5-fluorouracil and vincristine. He developed metabolic acidosis and hyperglycemia during chemotherapy. In addition, he developed anemia, thrombocytopenia and febrile neutropenia. He underwent a combined liver-kidney transplant for local control of his tumor and to treat MMA. He remains in remission more than five years after his transplant. In addition, his transplant has cured his MMA and he is able to tolerate a regular diet without developing metabolic crises.

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.

Correction of methylmalonic aciduria in vivo using a codon-optimized lentiviral vector

Methylmalonic aciduria is a rare disorder of organic acid metabolism with limited therapeutic options, resulting in high morbidity and mortality. Positive results from combined liver/kidney transplantation suggest, however, that metabolic sink therapy may be efficacious. Gene therapy offers a more accessible approach for the treatment of methylmalonic aciduria than organ transplantation. Accordingly, we have evaluated a lentiviral vector-mediated gene transfer approach in an in vivo mouse model of methylmalonic aciduria. A mouse model of methylmalonic aciduria (Mut(-/-)MUT(h2)) was injected intravenously at 8 weeks of age with a lentiviral vector that expressed a codon-optimized human methylmalonyl coenzyme A mutase transgene, HIV-1SDmEF1αmurSigHutMCM. Untreated Mut(-/-)MUT(h2) and normal mice were used as controls. HIV-1SDmEF1αmurSigHutMCM-treated mice achieved near-normal weight for age, and Western blot analysis demonstrated significant methylmalonyl coenzyme A enzyme expression in their livers. Normalization of liver methylmalonyl coenzyme A enzyme activity in the treated group was associated with a reduction in plasma and urine methylmalonic acid levels, and a reduction in the hepatic methylmalonic acid concentration. Administration of the HIV-1SDmEF1αmurSigHutMCM vector provided significant, although incomplete, biochemical correction of methylmalonic aciduria in a mouse model, suggesting that gene therapy is a potential treatment for this disorder.

Renal involvement in a patient with cobalamin A type (cblA) methylmalonic aciduria: a 42-year follow-up

Chronic renal failure is a well-known long-term complication of methylmalonic aciduria (MMA-uria), occurring even under apparently optimal metabolic management. The onset of renal dysfunction seems to be dependent on the type of defect and vitamin B12-responsiveness. We report on a patient with a vitamin B12-responsive cobalamin A type (cblA) MMA-uria caused by a homozygous stop mutation (p.R145X) in the cobalamin A gene (MMAA). She was diagnosed with chronic kidney disease (CKD) stage III at the age of 12 years. Following re-evaluation, the patient received vitamin B12 (hydroxocobalamin) treatment, resulting in a significant decrease in the concentration of methylmalonic acid (MMA) in urine and plasma. Until age 29 years glomerular filtration rate remained stable probably due to hydroxocobalamin treatment slowing down progression to end-stage renal failure. Kidney biopsies showed non-specific manifestations of chronic interstitial inflammation. The patient received a renal transplant at age 35 years. Under continuous treatment with hydroxocobalamin there is no evidence of kidney damage due to MMA-uria until the last follow-up 6 years after transplantation. This case report illustrates (i) a long-term follow-up of a patient with MMA-uria due to cblA deficiency, (ii) the involvement of the kidney as a target organ and (iii) the importance of early and adequate vitamin B12 substitution in responsive patients. Further investigation will be necessary to prove the protective effect of hydroxocobalamin in the kidney in vitamin B12-responsive patients.

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 growth in isolated methylmalonic acidemia

PURPOSE

We sought to predict renal growth based on clinical and metabolic parameters in patients with isolated methylmalonic acidemia, a group of disorders associated with chronic kidney disease.

METHODS

Fifty patients with methylmalonic acidemia, followed from 2004 to 2011, were classified by molecular genetics and studied using a combined cross-sectional and longitudinal design that included renal ultrasound examinations, anthropometric measurements, and metabolic phenotyping. Renal length was compared with that of healthy controls and modeled to other clinical parameters using multiple-regression analyses.

RESULTS

Comparisons with age-matched controls showed that renal length in subjects with methylmalonic acidemia was significantly decreased (P < 0.05). Stepwise regression modeling found that combinations of height, serum cystatin C, and serum methymalonic acid concentrations best predicted kidney size. The regression equations used to generate methylmalonic acidemia kidney nomograms were renal length (cm) = 6.79 + 0.22 × age for the controls and 6.80 + 0.09 × age for the methylmalonic acidemia cohort (P < 0.001; constant and slope).

CONCLUSION

Renal length, reflective of kidney growth, significantly decreased in patients with methylmalonic acidemia over time as compared with controls and was predictable with select clinical parameters. Cystatin C and serum methylmalonic acid concentrations were highly correlated with smaller kidneys and decreased renal function in this patient population.

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.

Acute renal failure potentiates methylmalonate-induced oxidative stress in brain and kidney of rats

Tissue methylmalonic acid (MMA) accumulation is the biochemical hallmark of methylmalonic acidemia. The disease is clinically characterized by progressive neurological deterioration and kidney failure, whose pathophysiology is still unclear. In the present work we investigated the effects of acute MMA administration on various parameters of oxidative stress in cerebral cortex and kidney of young rats, as well as the influence of acute renal failure on MMA-elicited effects on these parameters. Acute renal failure was induced by gentamicin, an aminoglycoside antibiotic whose utilization over prolonged periods causes nephrotoxicity. The administration of gentamicin alone increased carbonyl content and inhibited superoxide dismutase (SOD) activity in cerebral cortex, as well as increased thiobarbituric acid-reactive substances (TBA-RS) and sulfhydryl levels and diminished glutathione peroxidase activity in kidney. On the other hand, MMA administration increased TBA-RS levels in cerebral cortex and decreased SOD activity in kidney. Furthermore, the simultaneous administration of MMA and gentamicin to the rats provoked an augment in TBA-RS levels and superoxide generation in cerebral cortex and in TBA-RS, carbonyl and sulfhydryl levels in kidney, while diminished SOD activity in both studied tissues. Finally, nitrate/nitrite content, reduced glutathione levels, 2',7'-dihydrodichlorofluorescein oxidation and catalase activity were not affected by this animal treatment in either tissue. In conclusion, our present data are in line with the hypothesis that MMA acts as a toxin in brain and kidney of rats and suggest that renal injury potentiates the toxicity of MMA on oxidative stress parameters in brain and peripheral tissues.

Gene therapy in a murine model of methylmalonic acidemia using rAAV9-mediated gene delivery

Methylmalonic acidemia (MMA), an inherited metabolic disorder caused by deficient activity of methylmalonyl-CoA mutase, carries a poor prognosis for long-term survival. While administration of a recombinant adeno-associated virus serotype 8 vector (rAAV8) can rescue Mut(-/-) mice from neonatal lethality and provide sustained phenotypic correction, translation of gene therapy to human subjects will likely require multiple rounds of systemic administration and, ideally, the use of a vector that transduces the kidney. To examine the effectiveness of alternative rAAVs in the treatment of MMA, a serotype 9 rAAV expressing the Mut cDNA was constructed and delivered to newborn Mut(-/-) mice (n=11). rAAV9 gene therapy directed hepatic transgene expression within 24 h and effectively rescued the Mut(-/-) mice from lethality, conferred long-term survival, markedly improved metabolism and resulted in striking preservation of renal function and histology. Systemic readministration of the vector at a dose similar to that used in human clinical trials (2.5 × 10(9) GC of rAAV9 per gram) to older, treated Mut(-/-) mice (n=5) lowered circulating metabolites, increased in vivo propionate oxidative capacity and produced transgene expression in the kidney and liver. Our data support the use of an rAAV9 vector in the acute and chronic treatment of MMA, and highlight the renal tropism afforded by this novel serotype.

Renal transplantation in a boy with methylmalonic acidaemia

We present the first reported case of B(12) non-responsive methylmalonic acidaemia due to MMAB mutation to undergo an isolated renal transplant for renal failure. At 8 years of age he was listed for a combined liver and kidney transplant following progressive renal impairment. His metabolic control deteriorated with declining renal function and he was commenced on haemodialysis, leading to marked symptomatic and biochemical improvement. He was therefore relisted for isolated cadaveric renal transplant instead. He underwent successful renal transplantation at 12 years of age and now 6 years post transplant he is enjoying a more normal lifestyle with a marked reduction in plasma methylmalonate.

Long-term needs of adult patients with organic acidaemias: outcome and prognostic factors

BACKGROUND

With improvements in the treatment of children with organic acidaemias (OA), the number surviving to adulthood is increasing. To plan appropriate services for their care it is important to know what their needs are.

OBJECTIVE

To describe the clinical and social problems affecting adult patients with OA.

PATIENTS AND METHODS

We reviewed the medical records of 15 adult patients diagnosed with OA. Social attainment (housing, schooling and occupation) was analysed. Nutritional status was evaluated by body mass index (BMI) and laboratory studies. Neurological and visceral complications were noted. Cognitive outcome was evaluated by psychometric testing and/or educational attainment.

RESULTS

Seven had methylmalonic acidaemia (MMA), 4 isovaleric acidaemia (IVA) and 4 propionic acidaemia (PA). Ten were female, and median age was 23.5 years (range 18-48). All but three had late-onset disease. Two patients became pregnant during follow up. Four patients had obtained university degrees and were working. Three-quarters of the patients required some kind of social support. All had a good nutritional status. Height was normal in IVA and 3 PA patients. Osteoporosis was present in 2 out of 8 patients assessed. A variety of neurocognitive or visceral complications were seen in two-thirds of the patients. Metabolic decompensations were unusual.

CONCLUSIONS

The approach to adult patients with OA has to be multidisciplinary, with the clinician and dietician as the core of the team, but with the collaboration of clinical nurses specialists, social workers and other specialist services and the support of a biochemical and molecular laboratory.

Disease recurrence in paediatric renal transplantation

Renal transplantation (Tx) is the treatment of choice for end-stage renal disease. The incidence of acute rejection after renal Tx has decreased because of improving early immunosuppression, but the risk of disease recurrence (DR) is becoming relatively high, with a greater prevalence in children than in adults, thereby increasing patient morbidity, graft loss (GL) and, sometimes, mortality rate. The current overall graft loss to DR is 7-8%, mainly due to primary glomerulonephritis (70-80%) and inherited metabolic diseases. The more typical presentation is a recurrence of the full disease, either with a high risk of GL (focal and segmental glomerulosclerosis 14-50% DR, 40-60% GL; atypical haemolytic uraemic syndrome 20-80% DR, 10-83% GL; membranoproliferative glomerulonephritis 30-100% DR, 17-61% GL; membranous nephropathy approximately 30% DR, approximately 50% GL; lipoprotein glomerulopathy approximately 100% DR and GL; primary hyperoxaluria type 1 80-100% DR and GL) or with a low risk of GL [immunoglobulin (Ig)A nephropathy 36-60% DR, 7-10% GL; systemic lupus erythematosus 0-30% DR, 0-5% GL; anti-neutrophilic cytoplasmic antibody (ANCA)-associated glomerulonephritis]. Recurrence may also occur with a delayed risk of GL, such as insulin-dependent diabetes mellitus, sickle cell disease, endemic nephropathy, and sarcoidosis. In other primary diseases, the post-Tx course may be complicated by specific events that are different from overt recurrence: proteinuria or cancer in some genetic forms of nephrotic syndrome, anti-glomerular basement membrane antibodies-associated glomerulonephritis (Alport syndrome, Goodpasture syndrome), and graft involvement as a consequence of lower urinary tract abnormality or human immunodeficiency virus (HIV) nephropathy. Some other post-Tx conditions may mimic recurrence, such as de novo membranous glomerulonephritis, IgA nephropathy, microangiopathy, or isolated specific deposits (cystinosis, Fabry disease). Adequate strategies should therefore be added to kidney Tx, such as donor selection, associated liver Tx, plasmatherapy, specific immunosuppression protocols. In such conditions, very few patients may be excluded from kidney Tx only because of a major risk of DR and repeated GL. In the near future the issue of DR after kidney Tx may benefit from alternatives to organ Tx, such as recombinant proteins, specific monoclonal antibodies, cell/gene therapy, and chaperone molecules.

Combined liver-kidney transplant for the management of methylmalonic aciduria: a case report and review of the literature

Over 27 cases of liver transplant, kidney transplant and combined liver-kidney transplant have been reported for the treatment of methylmalonic aciduria. We describe a case of a 5-year-old boy who underwent combined liver-kidney transplant (CLKT) for phenotypic mut0 disease. His history was notable for more than 30 hospitalizations for severe acidosis, metabolic strokes, liver disease, pancreatic disease, chronic renal insufficiency with interstitial nephritis, and decreased quality of life. Post-CLKT, there was a marked reduction in serum (80%) and urine MMA levels (90%) as well as a cessation of metabolic decompensations. Neurologic deterioration continued post-CKLT manifested as a cerebellar stroke. The clinical details and therapeutic implications of solid organ transplant for methylmalonic aciduria are discussed.

Renal transplant in methylmalonic acidemia: could it be the best option? Report on a case at 10 years and review of the literature

Methylmalonic acidemia (MMA) is an inborn error of organic acid metabolism. Patients with severe disease develop many complications despite treatment; often, the disease progresses to severe damage of the central nervous system or to end-stage renal disease (ESRD). When medical treatment is ineffective, liver, kidney, or combined liver and kidney transplantation is advocated. At present, there are no definite guidelines as for the organ to be transplanted, and results are inconsistent. We report on a 27-year-old woman with MMA MUT0. The clinical symptoms developed at age 4 months. She progressed to ESRD and received a kidney transplant in November 1996 at age 17 years. One hundred and twenty months after transplant, renal function is normal; although urinary levels of methylmalonic acid are above normal limits, no episodes of metabolic decompensation have been observed after transplantation. Although liver is the major site of methylmalonyl-CoA mutase activity, this case and similar ones in the literature suggest that the smaller mutase activity present in the transplanted kidney may be sufficient to ensure partial correction of the metabolism of organic acids sufficient to prevent the onset of episodes of metabolic decompensation. It is worth investigating whether kidney transplant can be a safer and more satisfactory alternative to liver transplantation in cases of MMA unresponsive to medical treatment although urine MMA excretion remains significantly elevated.

Current role of liver transplantation for methylmalonic acidemia: a review of the literature

To evaluate the current role of liver transplantation (LT) for methylmalonic acidemia (MMA), we reviewed the literature on outcomes of this treatment, and describe three of our own cases of living-donor liver transplantation (LDLT). The total number of LT cases identified was 18. Transplantation mode was deceased donor LT in 12, including five combined liver-kidney transplantations (CLKT) from deceased donors, and LDLT in six. Three hospital mortalities were noted, because of metabolic decompensation, sepsis and aspergillosis. Although mean postoperative serum MMA level decreased to 13.8% +/- 9.2% (range 1.25-26.1%) of preoperative levels, four patients (22.2%) had renal insufficiency after isolated LT and three (16.7%) had postoperative neurological disability. Continuing metabolic damage to the kidney and brain may occur even after successful LT. Further evaluation is required to determine the long-term suitability of this treatment modality.

Liver transplantation is not curative for methylmalonic acidopathy caused by methylmalonyl-CoA mutase deficiency

Methylmalonic acidopathy resulting from severe methylmalonyl-CoA mutase deficiency causes acute, potentially lethal ketoacidotic episodes, renal failure, and acute and chronic neurologic disease. As dietary and alkali therapy is suboptimal, liver transplantation during infancy has been touted as a potential cure. However, reports in liver transplant recipients about new onset neurologic disease, in the absence of ketoacidosis, and progressive renal insufficiency have cast doubt about its effectiveness. We report the long-term (9 years) outcome for the first patient with severe methylmalonic acidopathy transplanted in the USA and provide new biochemical data that indicate why transplanted patients are still susceptible to "metabolic strokes". In our 10-year-old male patient, there is clear evidence that the de novo synthesis of propionyl-CoA within the CNS leads to brain methylmalonate (MMA) accumulation that is largely unaffected by transplantation. Liver replacement is not a cure for methylmalonic acidopathy.

Methylmalonic and propionic aciduria

Methylmalonic and propionic aciduria (PA) are the most frequent forms of branched-chain organic acidurias. These autosomal recessive disorders result from deficient activity of methylmalonyl-CoA mutase and propionyl-CoA carboxylase, respectively. Clinically, acute or chronic neurologic signs are caused by the accumulation of toxic compounds proximal to the metabolic block. Phenotype varies from severe neonatal-onset forms with high mortality and poor outcome to milder forms with a later onset. In both cases the clinical course is dominated by the risk of relapses of life-threatening episodes of metabolic decompensation and of severe organ failure. Despite improvement of treatment, the overall outcome remains disappointing with no major differences between the two diseases. The diagnosis is based on the presence of characteristic compounds in body fluids as detected by organic acid analysis in urine and acylcarnitine profile in blood. Therapy is based on low-protein high-energy diet, carnitine supplementation, and metronidazole. Some patients with methylmalonic aciduria (MMA) respond to pharmacological doses of vitamin B12. Given the poor long-term prognosis, liver transplantation has been recently attempted as an alternative therapy to conventional medical treatment to cure the underlying metabolic defect. Nevertheless, the overall experience to date does not clearly demonstrate its effectiveness in preventing further deterioration or improving survival and quality of life. The recent implementation of neonatal screening by electrospray tandem mass spectrometry has decreased early mortality and improved the short-term outcome, without changing the detection rate of both diseases in the screening population compared to clinically detected cases. However, the limited number of patients and the short duration of their follow-up do not yet permit drawing final conclusions on its effect on the long-term outcome of methylmalonic and propionic acidemia.

'Classical' organic acidurias, propionic aciduria, methylmalonic aciduria and isovaleric aciduria: long-term outcome and effects of expanded newborn screening using tandem mass spectrometry

'Classical organic acidurias' comprise isovaleric aciduria, propionic aciduria and methylmalonic aciduria. Available data from the literature suggest that the use of 'new' therapeutic strategies has improved survival but has not modified neurodevelopment. Progressive neurocognitive deterioration is almost invariably present in propionic and methylmalonic acidurias, while large-scale studies on the long-term outcome of patients with isovaleric aciduria are still lacking. In order to answer to some of the questions suggested by Wilson and Jungner in 1968 about the criteria of disease screening, we compared the natural history of patients with 'classical' organic acidurias diagnosed on clinical bases to those diagnosed through neonatal mass screening using tandem mass spectrometry. Decreased early mortality, less severe symptoms at diagnosis, and more favourable short-term neurodevelopmental outcome were recorded in patients identified through expanded newborn screening. The short duration of follow-up so far does not allow us to draw final conclusions about the effects of newborn screening on long-term outcome. The evaluation of the effect of neonatal screening on the detection rate of these three diseases showed that the incidence of isovaleric aciduria was significantly higher in the screening population than in clinically detected cases, with no changes for propionic and methylmalonic acidurias. Further multicentre longitudinal studies are needed to assess the usefulness of expanded newborn screening for 'classical' organic acidurias and to better understand the clinical spectrum of these diseases. This paper describes the long-term outcome and the impact of expanded newborn screening on the so-called 'classical' organic acidurias (propionic aciduria, methylmalonic aciduria and isovaleric aciduria).

Effect of docosahexaenoic acid administration on plasma lipid profile and metabolic parameters of children with methylmalonic acidaemia

AIM

To evaluate the effect of administration of docosahexaenoic acid (DHA) on dyslipidaemia, plasma fatty acid composition and metabolic parameters of children with isolated methylmalonic acidaemia (MMA) (McKusick 25100).

METHODS

Four children (3 male, 1 female) with MMA (mut(0)), participated in a crossover, randomized study of DHA administration (25 mg/kg per day, divided into three daily doses). The control group comprised 56 healthy children, aged 10+/- 2.7 years, (51 male, 5 female), who were followed in our clinic owing to possible familial risk of cardiovascular disease.

RESULTS

The comparison of plasma fatty acid composition of children with MMA versus control children demonstrated that the patients had significantly higher values for oleic acid (p = 0.004) and linolenic acid (p = 0.008). No differences were observed in the levels of DHA and arachidonic acid. Plasma concentrations of insulin, glycine, ammonia, total cholesterol and cholesterol fractions did not change with DHA administration. No significant changes were observed in urinary excretion of methylmalonic acid. As expected, the percentage of DHA and n-3 fatty acids in plasma increased significantly after therapy (p = 0.005 and 0.014, respectively). The most remarkable result was a decrease of plasma levels of triglycerides after DHA therapy (p = 0.014).

CONCLUSION

As previously found in normal children, dietary supplementation with DHA decreases the triglyceride levels, normalizing the hypertriglyceridaemia of these children without any evidence of short-term adverse effects.

Renal transplantation in a 14-year-old girl with vitamin B12-responsive cblA-type methylmalonic acidaemia

Renal tubular dysfunction and chronic renal failure are well recognised complications of methylmalonic acidaemia (MMA) and can occur even in the context of optimal medical metabolic management. Organ transplantation, such as renal and combined liver and renal transplants, have been utilised in the past for children whose disease cannot be managed by conservative medical practices and those with end stage renal disease. Our patient was diagnosed with B(12)-responsive MMA (subsequently proven to be cblA-type MMA) in the postoperative period following renal transplantation for idiopathic chronic renal failure. She remains well, with excellent graft function and metabolic control 4 years after transplantation. This patient highlights the importance of testing for the inborn errors of metabolism in patients presenting with recurrent acidosis and progressive renal impairment.

Propionic acidemia revisited: a workshop report

Propionic acidemia (PA) is one of the most frequent organic acidurias, but information on the outcome of individuals with PA is rather limited. We present data of 49 patients with PA, which were gathered from 18 metabolic centers throughout Central Europe on the occasion of an international workshop. All patients were identified by selective metabolic screening, and 86% of them were classified as having early-onset PA owing to their presentation with clinical symptoms within the first 90 days of life. Mortality rate was one third, and details of symptoms and treatment of the surviving patients are discussed. The great variation of phenotypic expression of the disease and different therapeutic strategies (especially in regard to the degree of protein restriction) used at the various institutions involved in this study imply the need for a registry of PA patients and for a multicenter prospective treatment study.

Pathophysiology, diagnosis, and treatment of methylmalonic aciduria-recent advances and new challenges

Classical methylmalonic aciduria is a relatively rare inborn error of branched-chain amino acid metabolism, occurring in 1:50,000 to 1:80,000 newborns. Three decades after its recognition, major progress has been made in survival and prevention of neurological sequelae in affected children, if the diagnosis is made early and treatment and follow-up care are meticulous. Therapy consists of a specially formulated protein diet, carnitine supplementation, and vigorous emergency treatment during intercurrent illnesses aimed at preventing the development of catabolism. Recently the clinician has been challenged by partially unexpected long-term complications. These include chronic neurological symptoms, specifically an extrapyramidal movement disorder caused by progressive destruction of the basal ganglia, which are similar to those observed in other organic acid disorders, such as propionic aciduria or glutaric aciduria type I. Unexpected and unique is the development of chronic renal failure in a major subset of patients. As the pathophysiological basis of renal failure is still obscure, no causative treatment is available and hemodialysis may become necessary. Experience with transplantation of liver, kidney, or kidney and liver is very limited and allows as yet no conclusions. Interdisciplinary research efforts in this field should reveal new pathophysiological links and hopefully provide additional therapeutic approaches.