Combined malonic and methylmalonic acidemia (CMAMMA) is a rare genetic disorder caused by biallelic variants in the acyl-CoA synthetase family member 3 (ACSF3) gene (Witkowski et al., 2011) and is associated with elevated levels of malonic acid (MA) and methylmalonic acid (MMA) in urine (Sloan et al., 2011). CMAMMA is generally considered a benign disorder, with recent descriptions of potential neuropsychiatric symptoms in children (Levtova et al., 2019). We expand the phenotype by describing a case of severe developmental and epileptic encephalopathy with a CMAMMA-associated Lennox-Gastaut Syndrome (LGS) phenotype and comorbid neuropsychiatric abnormalities. An 8-year-old boy with CMAMMA, referred to our clinic's neurogenetic center, presented with refractory epilepsy and severe neurobehavioral symptoms. His epilepsy consisted of tonic, atonic, and generalized tonic-clonic seizures with electroclinical features consistent with LGS. The patient had comorbid autism, aggression, and intellectual disability with a history of developmental regression. Genetic testing confirmed pathogenic biallelic ACSF3 variants, and urine organic acid testing showed elevated levels of MA and MMA in urine. This case suggests that CMAMMA can lead to severe epilepsy and a neuropsychiatric phenotype, expanding the clinical spectrum of the disorder.

Combined malonic and methylmalonic aciduria (CMAMMA) is an inherited metabolic disorder caused by ACSF3 variants leading to malonyl-CoA synthetase (MCS) deficiency. Despite its well-defined genetic basis, the clinical spectrum of CMAMMA remains highly variable. This study reports six patients from three unrelated families, aged 12 days to 30 years, presenting with heterogeneous clinical manifestations. Exome sequencing (ES) identified a homozygous ACSF3 variant, c.1470G>C [p.(Glu490Asp)], in five patients, and a novel variant, c.1145T>C [p.(Leu382Pro)], in one patient. Notably, in each family's index case, ES revealed additional pathogenic variants consistent with a dual molecular diagnosis: a homozygous CHRNG variant in one patient; compound heterozygous BTD variants in two siblings, confirming biotinidase deficiency; and a novel CDK10 frameshift variant, c.520_521del [p.(Lys174Glyfs*34)], in another patient. Half of the patients with CMAMMA demonstrated mild to moderate developmental delay. Notably, the sibling with both CMAMMA and biotinidase deficiency exhibited developmental delay, whereas the sibling with isolated CMAMMA had normal development. Symptomatic individuals showed clinical improvement following dietary protein restriction and carnitine supplementation. These findings highlight that CMAMMA may cause developmental delay, emphasizing the importance of early diagnosis and treatment. Furthermore, in patients with atypical features, high-throughput sequencing technologies offer a comprehensive approach to identifying additional pathogenic variants in genes beyond ACSF3.

Methylmalonic aciduria (MMA) is described by high methylmalonic acid concentrations in the blood and urine. This condition can be isolated or in combination with homocystinuria. While variants in the MMUT, MMAA, MMAB, MMADHC and MCEE genes contribute to the pathogenesis of the isolated form, variants in MMACHC, MMADHC, LMBRD1, and ABCD4 genes, are responsible for diverse types of combined MMA and homocystinuria. In the current study, we report molecular tests of 15 Iranian patients who had mutations in MMA-related genes. Among the assessed patients, MMACHC gene was the most prevalently mutated gene (mutated in 7 patients). Each of MMAA, MMAB, and MMUT genes were mutated in 2 patients, respectively. Finally, we detected variants in each of ACSF3 and ABCD4 genes in one case, respectively. Among the identified variants, five variants were not reported before. Cumulatively, the current study provides some data about MMA-related variants among Iranian patients.

Methylmalonic acidemia (MMAs) is known as a severe, complex, and lethal disorder of methylmalonate and cobalamin. The patients with MMA may have developmental, neurological, and metabolic disorders such as liver disease. Here, we aim to evaluate 6 Iranian patients suspected to MMA disorder. We will provide genetic results, biochemical analysis and treatment for these patients. Liquid chromatography-tandem mass spectrometry (LC-MS/MS) and variant screening in probands by whole exome sequencing (WES) were performed. A total of six homozygous variants were identified, including five previously identified variants and one novel variant, in the two MMA-causing genes as follows: c.577G > C, c.290 + 69G > T, c.662T > A, c.290 + 69G > T of MMAB, and c.100dupA, c.394 C > T of MMACHC. Sanger sequencing confirmed the identified variants. Additionally, metabolomics data analysis reliably identified elevated C3 and MMA levels, as well as abnormalities in the amino acid profile, indicating the presence of pathogenic variants. Our findings expand the global spectrum of genotypes in MMA. While WES, combined with metabolomics and biochemical analysis, offers valuable insights for accurate diagnosis and subtyping of MMA, it is most beneficial in complex cases where clinical findings are unclear.

Objective: To investigate the clinical features and outcomes of adolescence-onset methylmalonic acidemia (MMA) and explore preventive strategies. Methods: This was a retrospective case analysis of the phenotypes, genotypes and prognoses of adolescence-onset MMA patients. There were 55 patients diagnosed in Peking University First Hospital from January 2002 to June 2023, the data of symptoms, signs, laboratory results, gene variations, and outcomes was collected. The follow-ups were done through WeChat, telephone, or clinic visits every 3 to 6 months. Results: Among the 55 patients, 31 were males and 24 were females. The age of onset was 12 years old (range 10-18 years old). They visited clinics at Tanner stages 2 to 5 with typical secondary sexual characteristics. Nine cases (16%) were trigged by infection and 5 cases (9%) were triggered by insidious exercises. The period from onset to diagnosis was between 2 months and 6 years. Forty-five cases (82%) had neuropsychiatric symptoms as the main symptoms, followed by cardiovascular symptoms in 12 cases (22%), kidney damage in 7 cases (13%), and eye disease in 12 cases (22%). Fifty-four cases (98%) had the biochemical characteristics of methylmalonic acidemia combined with homocysteinemia, and 1 case (2%) had the isolated methylmalonic acidemia. Genetic diagnosis was obtained in 54 cases, with 20 variants identified in MMACHC gene and 2 in MMUT gene. In 53 children with MMACHC gene mutation,1 case had dual gene variants of PRDX1 and MMACHC, with 105 alleles. The top 5 frequent variants in MMACHC were c.482G>A in 39 alleles (37%), c.609G>A in 17 alleles (16%), c.658_660delAAG in 11 alleles (10%), c.80A>G in 10 alleles (10%), c.567dupT and c.394C>T both are 4 alleles (4%). All patients recovered using cobalamin, L-carnitine, betaine, and symptomatic therapy, and 54 patients (98%) returned to school or work. Conclusions: Patients with adolescence-onset MMA may triggered by fatigue or infection. The diagnosis is often delayed due to non-specific symptoms. Metabolic and genetic tests are crucial for a definite diagnosis. Treatment with cobalamin, L-carnitine, and betaine can effectively reverse the prognosis of MMA in adolescence-onset patients. 目的： 探讨青春期起病的迟发型甲基丙二酸血症患儿的临床特点、诊断治疗及随访。 方法： 回顾性病例分析。选择2002年1月至2023年6月于北京大学第一医院确诊的青春期起病的55例甲基丙二酸血症患儿为研究对象，收集患儿症状、体征、检验结果、基因变异等临床资料，每3或6个月通过微信、电话或门诊进行随访（截至2023年12月），对患儿的临床表型、基因型及转归进行总结。 结果： 55例患儿中男31例、女24例，于10~18岁发病，中位发病年龄为12岁，第二性征发育均正常，就诊时Tanner 2~5期。9例（16%）在感染后起病，5例（9%）在剧烈运动后起病，从发病到确诊的时间历经2个月至6年。45例（82%）主要表现为神经精神疾病，12例（22%）出现心血管损伤，7例（13%）出现肾脏损伤，12例（22%）合并眼病。54例（98%）患甲基丙二酸血症合并同型半胱氨酸血症，1例患单纯型甲基丙二酸血症（2%）。54例获得了基因诊断，发现20种MMACHC基因变异和2种MMUT基因变异。53例MMACHC基因变异患儿中，1例为PRDX1和MMACHC双基因变异，共105个等位基因变异，前5位高频度变异为39个（37%）c.482G>A、17个（16%）c.609G>A、11个（10%）c.658_660delAAG、10个（10%）c.80A>G、4个（4%）c.567dupT和4个（4%）c.394C>T。所有患儿经过钴胺素、左卡尼汀、甜菜碱和对症治疗后逐渐康复，54例（98%）恢复正常就学和工作。 结论： 青春期起病的甲基丙二酸血症患儿多为合并型，发病隐匿，部分因疲劳或感染诱发疾病，临床识别困难，容易被延误诊断。生化代谢和基因检测是获得正确诊断的关键，通过钴胺素、左卡尼汀和甜菜碱治疗可以显著改善病情。.