Genetic testing is necessary for correct diagnosis and treatment in patients with isolated methylmalonic aciduria: a case report

Background Isolated methylmalonic aciduria can be caused by pathogenic mutations in the gene for methylmalonyl-CoA mutase or in the genes encoding enzymes involved in the intracellular metabolism of cobalamin. Some of these mutations may be cobalamin responsive. The type of methylmalonic aciduria cannot always be assumed from clinical manifestation and the responsiveness to cobalamin has to be assessed for appropriate cobalamin administration, or to avoid unnecessary treatment. The cases presented herein highlight the importance of genetic testing in methylmalonic aciduria cases and the need for standardisation of the in vivo cobalamin-responsiveness assessment. Case presentation We describe two patients who presented in the first week of life with rapid neurological deterioration caused by metabolic acidosis with severe hyperammonaemia requiring extracorporeal elimination in addition to protein restriction, energy support, carnitine, and vitamin B12 treatment. The severity of the clinical symptoms and high methylmalonic acid concentrations in the urine (>30,000 μmol/mmol of creatinine) without hyperhomocysteinaemia in both of our patients suggested isolated methylmalonic aciduria. Based on the neonatal manifestation and the high methylmalonic acid urine levels, we assumed the cobalamin non-responsive form. The in vivo test of responsiveness to cobalamin was performed in both patients. Patient 1 was evaluated as non-responsive; thus, intensive treatment with vitamin B12 was not used. Patient 2 was responsive to cobalamin, but the dose was decreased to 1 mg i.m. every two weeks with daily oral treatment due to non-compliance. Genetic tests revealed bi-allelic mutations in the genes MMAB and MMAA in Patient 1 and 2, respectively. Based on these results, we were able to start intensive treatment with hydroxocobalamin in both patients. After the treatment intensification, there was no acute crisis requiring hospitalisation in Patient 1, and the urine methylmalonic acid levels further decreased in Patient 2. Conclusions Despite carrying out the in vivo test of responsiveness to cobalamin in both patients, only the results of molecular genetic tests led us to the correct diagnosis and enabled intensive treatment with hydroxocobalamin. The combination of the standardized in vivo test of cobalamin responsiveness and genetic testing is needed for accurate diagnosis and appropriate treatment of isolated methylmalonic aciduria.

Physical and Neurological Development of a Girl Born to a Mother with Methylmalonic Acidemia and Kidney Transplantation and Review of the Literature

Background: actual literature suggests that children of methylmalonic acidemia patients are mostly healthy, but data are only partial, especially regarding long-term outcome. Therefore, our aim was to evaluate the possible long-term neurological effects of fetal exposure to high levels of methylmalonic acid in a child of a renal transplant recipient. Methods: we retrospectively evaluated the clinical and neurological records of a girl whose mother is a kidney transplant recipient affected by methylmalonic acidemia. Subsequently, we compared our results with the ones already published. Results: the girl’s weight and stature were within the normal range in the first years of life but, starting from 4 years of age, she became progressively overweight. Regarding the neurodevelopment aspects, for the first time we performed a complete and seriated neuropsychological evaluation, highlighting a mild but significant weakness in the verbal domain, with a worsening trend at three-year revaluation. Conclusions: since children of MMA patients are exposed to methylmalonic acid, the efforts of the physicians caring for these children should be directed on careful evaluation of growth, prevention of obesity and regular neurological examination together with structured neuropsychological tests to achieve a better insight in possible complications of pregnancy in patients suffering from this condition.

Progressive Imbalance and Visual Impairment in a Patient With Diabetes

A 72-year-old man with hypothyroidism and type 2 diabetes sought care for a 3-year history of slowly progressive, ascending lower limb paresthesias and imbalance. Three months earlier, he noted subacute onset of finger numbness and substantial worsening of imbalance with infrequent falls. He also had a 1-year history of progressive visual decline that persisted despite cataract surgery. Additional symptoms included intermittent light-headedness and confusion. Laboratory evaluations showed a decreased hemoglobin value and an increased mean corpuscular volume. Macrocytic red blood cells were noted on a peripheral blood smear. Serum vitamin B12 level was less than 70 ng/L. Levels of plasma homocysteine and serum methylmalonic acid were markedly increased to 375 µmol/L and 143 nmol/L, respectively. Serum copper level was normal. Serum parietal cell antibodies were increased to 46 U, and intrinsic factor antibodies were absent. Serum gastrin was markedly increased. The clinical presentation in this patient suggested a myeloneuropathy. His vitamin B12 level was undetectable and accompanied by a macrocytic anemia and increased methylmalonic acid and homocysteine levels. Even though intrinsic factor antibodies were negative, the clinical picture was supportive of subacute combined degeneration in the setting of pernicious anemia. The patient was started on vitamin B12 replacement. At 6-month follow-up he had striking improvement in gait and vision. The light-headedness and confusion were no longer present. His examination was remarkable only for mild impairment, with tandem gait and a slightly positive Romberg sign. The lower limb reflexes were reduced. Impaired position perception at the toes persisted, but vibration perception in the lower limbs improved. Laboratory investigations showed normalization of the hemoglobin, vitamin B12, methylmalonic acid, and homocysteine levels. The serum gastrin level had improved but was still increased at 742 pg/mL. The best-characterized neurologic manifestations of vitamin B12 deficiency include myelopathy and myeloneuropathy. Autonomic neuropathy, optic neuropathy, and neuropsychiatric manifestations have also been reported. Neurologic manifestations may occur without evidence of the characteristic hematologic derangement, megaloblastic anemia. Macrocytosis or hypersegmented neutrophils on peripheral blood smear may be clues.

Methylmalonic acid impairs cell respiration and glutamate uptake in C6 rat glioma cells

ABSTRACTMethylmalonic acidemia is an organic acidemia caused by deficient activity of L-methylmalonyl-CoA mutase or its cofactor cyanocobalamin and it is biochemically characterized by an accumulation of methylmalonic acid (MMA) in tissue and body fluids of patients. The main clinical manifestations of this disease are neurological and observable symptoms during metabolic decompensation are encephalopathy, cerebral atrophy, coma, and seizures, which commonly appear in newborns. This study aimed to investigate the toxic effects of MMA in a glial cell line presenting astrocytic features. Astroglial C6 cells were exposed to MMA (0.1-10mM) for 24 or 48 hours and cell viability, glucose consumption and oxygen consumption rate, as well as glutamate uptake and ATP content were analyzed. The possible preventive effects of bezafibrate were also evaluated. MMA significantly reduced cell viability after 48-hour period and increased glucose consumption during the same period of incubation. Regarding the energy homeostasis, MMA significantly reduced respiratory parameters of cells after 48-hour exposition, indicating that cell metabolism is compromised at resting and reserve capacity state, which might influence the cell capacity to meet energetic demands. Glutamate uptake and ATP content were also compromised after exposition to MMA, which can be influenced energy metabolism impairment, affecting the functionality of the astroglial cells. Our findings suggest that these effects could be involved in the pathophysiology of neurological dysfunction of this disease.

Oral administration of cyanocobalamin for functional vitamin В12 deficiency: efficacy and safety

The prevalence of vitamin В12 deficiency is about 3—16% in the general population, while in older people, it ranges from 10 to 20%. An increase in the proportion of people on reduced-calorie diets, the widespread use of drugs that can result in vitamin В12 deficiency, an increase in life expectancy, on the one hand, a variety of clinical manifestations and the lack of precise algorithms for laboratory diagnostics, on the other hand, suggest that the number of patients with vitamin В12 deficiency is significantly higher. Vitamin В12 can be absorbed by passive diffusion, regardless of intrinsic factor and other underlying causes of the deficiency. The presence of an additional route of absorption brings in new expectations for the oral administration of cyanocobalamin in therapeutic doses. Comparative clinical trials of the use of cyanocobalamin have shown that the oral route of administration is as effective as the parenteral. Considering the need for long-term, and in some cases — life-long, use of the drug, there is a need to develop dosage regimens for oral administration comparable in effectiveness to parenteral administration. The use of functional vitamin В12 deficiency biomarkers, such as vitamin В12 levels, cholotranscobalamin, methylmalonic acid, homocysteine, made it possible to establish that a daily dose of 1000 mkg is the most effective, which at the initial stage is as efficient as intramuscular administration. In some circumstances, maintenance therapy (intramuscularly at a dose of 1 mg/month) was more effective; thus, a differentiated approach scheme to determining the maintenance oral dose was proposed, depending on the result obtained at the initial stage of therapy. Comparative studies covering the entire spectrum from the recommended dietary allowance to the dose commonly used for cobalamin injections have shown that an oral daily dose of 1000 mcg of cyanocobalamin normalizes serum vitamin В12 levels and causes an 80—90% decrease in plasma methylmalonic acid concentration from the assumed maximum value. The oral route of administration provides a higher patient treatment adherence.

Testing and Prescribing Vitamin B12 in Swiss General Practice: A Survey among Physicians

Testing and prescribing vitamin B12 (also known as cobalamin) is increasing in Switzerland but substantial variation among general practitioners (GPs) with respect to testing has been noted. In this study, we aimed at exploring GPs’ mindsets regarding vitamin B12 testing and prescribing. A cross-sectional study was conducted using an online survey distributed by e-mail to Swiss GPs. The questionnaire explored mindsets related to testing and prescribing vitamin B12 in specific clinical situations, as well as testing and prescribing strategies. The questionnaire was sent to 876 GPs and 390 GPs responded (44.5%). The most controversial domains for testing and prescribing vitamin B12 were idiopathic fatigue (57.4% and 43.4% of GPs agreed, respectively) and depressive symptoms (53.0% and 35.4% of GPs agreed, respectively). There was substantial variation among GPs with regard to testing strategies (89.5% of GPS used a serum cobalamin test, 71.3% of GPS used holotranscobalamin, and 27.6% of GPs used homocysteine or methylmalonic acid). Intramuscular injection was the predominantly prescribed route of application (median of 87.5% of the prescriptions). In this study, we focus on discordant mindsets that can be specifically targeted by using educational interventions, and research questions that still need answering specifically about the effectiveness of vitamin B12 for idiopathic fatigue.

VITAMIN B12 AND FOLIC ACID STATUS AMONG DISPLACED PREGNANT WOMEN ATTENDING ANTENATAL CARE CLINIC IN DOMIZ CAMP OF A SYRIAN REFUGEES /KURDISTAN REGION, IRAQ

Background: Vitamin B12, folic acid and their relevant biomarkers are essential micronutrients for healthy fetal growth and development. Thus, deficiency in the levels of these vitamins and relevant biomarkers during pregnancy leads to many adverse outcomes for both mother and fetus. Objective: The current research project aims to detect the status of vitamin B12 and Folic acid and relevant biomarkers such as Homocysteine, Methylmalonic acid and Holotranscobalamin among displaced pregnant women attending antenatal care in Domiz Camps Clinic of Syrian refugees. Methods and Subjects: This cross-sectional research was performed at Syrian refugee’s camps in Domiz- Duhok city, Kurdistan Region, Iraq, from February 2019 until June 2019. This study included 540 pregnant women whose ages ranged between 15-44 years. Participants were subdivided into three groups based on their trimesters. Each group included 180 pregnant women. Vitamin B12 and folic acid were measured by Automatic Clinical Chemistry Analyzer COBAS 6000 while Methylmalonic acid (MMA), Homocysteine (Hcy), and Holotranscobalamin (HoloTc) were measured by ELISA. Results: The results of the current study revealed that the prevalence of vitamin B12 insufficiency (<200 pg/mL) was high across all three trimesters, which constitutes 73% in the total cohort. The mean vitamin B12 (pg/mL) during 1st semester was within the normal range (226.5± 6.95), whereas during the 2nd and 3rd semesters it was significantly (P<0.0001) low (179.25± 4.52 and 151.60±4.32, respectively). Prevalence of folic acid (ng/ml) insufficiency (<3.8 ng/mL) was 11.5% in total subjects and means of folic acid during the 3 semesters were 11.2± 0.41, 11.0± 0.41 and 9.2±0.41), respectively. Methylmalonic acid levels (umol/L) also showed a highly significant (P < 0.001) differences between the three semesters. The mean MMA levels during the three semesters were 0.130±0.003, 0.142±0.002, and 0.154± 0.003, respectively. Whereas homocysteine (umol/L) showed non-significant (P=0.2085) differences between all trimesters; and their levels were 7.6± 0.45, 8.0± 0.39, and 8.6± 0.42. respectively. Furthermore, Holotranscobalamin also showed non-significant (P=0.883) difference between studied trimesters; and its level during the three trimesters were 137.4± 2.86, 135.1± 3.25 and 137.16± 4.20 pmol/l, respectively. From the total sum, 22.2% of the total pregnant women showed an increased MMA level (more than 0.280 umol/l), and 18.5% of the total participant showed an elevated level of Hcy (more than 15 umol/l). Whereas as only 7.9% of 540 pregnant women showed low level of HoloTc less than 40 pmol/l. From the total cohort, only 7.03% showed combining lowered HoloTc level plus elevated MMA and Hcy level which indicates the manifestation of vitamin B12 deficiency during pregnancy.