Evaluation of the clinical, biochemical, genotype and prognosis of mut-type methylmalonic acidemia in 365 Chinese cases.

BACKGROUND: Methylmalonic acidemia (MMA), which results from defects in methylmalonyl-CoA mutase (mut type) or its cofactor, is the most common inherited organic acid metabolic disease in China. This study aimed to investigate the phenotype and genotype of mut-type MMA in Chinese patients. METHODS: We recruited 365 patients with mut-type MMA; investigated their disease onset, newborn screening (NBS) status, biochemical metabolite levels, gene variations and prognosis; and explored the relationship between phenotype and genotype. RESULTS: There were 152 patients diagnosed by tandem mass spectrometry (MS/MS) expanded NBS, 209 patients diagnosed because of disease onset without NBS and 4 cases diagnosed because of sibling diagnosis. The median age of onset was 15 days old, with a variety of symptoms without specificity. Urinary levels of methylmalonic acid and methylcitric acid (MCA) decreased after treatment. Regarding the prognosis, among the 152 patients with NBS, 50.6% were healthy, 30.3% had neurocognitive impairment and/or movement disorders and 13.8% died. Among the 209 patients without NBS, 15.3% were healthy, 45.9% had neurocognitive impairment and/or movement disorders and 33.0% died. In total, 179 variants were detected in the MMUT gene, including 52 novel variations. c.729_730insTT, c.1106G>A, c.323G>A, c.914T>C and c.1663G>A were the five most frequent variations. The c.1663G>A variation led to a milder phenotype and better prognosis. CONCLUSION: There is a wide spectrum of variations in the MMUT gene with several common variations. Although the overall prognosis of mut-type MMA was poor, participation in MS/MS expanded NBS, vitamin B12 responsive and late onset are favourable factors for the prognosis.

[Analysis of TBX19 gene variant in a child with congenital isolated adrenocorticotropic hormone deficiency].

OBJECTIVE: To analyze the clinical and genetic characteristics of a patient with congenital isolated adrenocorticotropic hormone deficiency (IAD). METHODS: Clinical characteristics of the patient was reviewed. Genomic DNA of the child was subjected to whole exome sequencing. RESULTS: Genetic testing has confirmed the diagnosis of congenital IAD by identification of compound heterozygous variants of the TBX19 gene, which included a pathogenic nonsense c.535C>T (p.R179X) variant inherited from his father and a novel missense c.298C>T (p.R100C) variant inherited from his mother. CONCLUSION: Congenital IAD due to variants of the TBX19 gene is a rare autosomal recessive disease. It is characterized by low plasma adrenocorticotropic hormone and cortisol levels but normal levels of other pituitary hormones. Delayed diagnosis may lead to severe early-onset adrenal failure and wrong treatment which may result in neonatal mortality. Hydrocortisone replacement is effective. Detection of pathogenic variant of TBX19 gene is the key to diagnosis.

Clinical and genetic characteristics of Keishi-Bukuryo-Gan syndrome: an analysis of 5 cases.

: To analyze the clinical and genetic characteristics of children with Keishi-Bukuryo-Gan (KBG) syndrome. The clinical and genetic data of 5 children with KBG syndrome admitted in Children's Hospital Affiliated of Zhengzhou University from November 2018 to September 2020 were retrospectively analyzed. Five children were all males who came from four different families. All children presented triangular face, bushy eyebrows, thin upper lip, large or delayed closure of anterior fontanel, and abnormal bone development. Four cases had growth retardation, large ears, thick ear lips; 3 cases had large central incisors; 2 cases had congenital heart disease; 2 cases had abnormal skin changes; 2 cases had genital changes; and 2 cases became grumpy. Liver and kidney function,thyroid function, blood gas analysis and electrolyte of the children were all in the normal range. Three children received bone age examination, and all showed bone age lag. Two cases showed backward myelination of white matter in MRI. Whole exome sequencing revealed that all 5 children had heterozygous mutations in the gene, among which c.6836_6837delTG, c.5866C>T, and c.6270delT were newly discovered mutation sites. None of the parents of probands were found to carry the mutations in gene. Two cases achieved height catch-up and cognitive improvement after treatment with recombinant human growth hormone. KBG syndrome is characterized by a wide spectrum of phenotypes, and large or delayed closure of the anterior fontanel, large ears and thick ear lips may be the main manifestations of the disease in infants and young children. gene mostly presents spontaneous mutations, and early application of growth hormone therapy can achieve height catch-up and cognitive improvement without obvious adverse reactions.

[Clinical and genetic analysis of a case of dihydrolipoamide dehydrogenase deficiency caused by novel variant of DLD gene].

OBJECTIVE: To analyze the clinical and genetic characteristics of a patient with dihydrolipoamide dehydrogenase deficiency. METHODS: Potential variants of the DLD gene were detected by whole exome sequencing and verified by Sanger sequencing. RESULTS: Compound heterozygous variants, c.704_705delTT (p.Leu235Argfs*8) and c.1058T>C (p.Ile353Thr), were detected in the DLD gene. The c.1058T>C (p.Ile353Thr) variant was derived from his mother and known to be pathogenic. The c.704_705delTT (p.Leu235Argfs*8) variant was derived from his father and was unreported previously. CONCLUSION: The compound heterozygous variants of c.704_705delTT (p.Leu235Argfs*8) and c.1058T>C (p.Ile353Thr) of the DLD gene probably underlay the disease in this patient. Above finding has facilitated genetic counseling and prenatal diagnosis for the family.

A novel stop-loss DAX1 variant affecting its protein-interaction with SF1 precedes the adrenal hypoplasia congenital with rare spontaneous precocious puberty and elevated hypothalamic-pituitary-gonadal/adrenal axis responses.

The case study unveils the likely mechanism of a novel stop-loss DAX1 variant preceding the prolonged precocious puberty in the adrenal hypoplasia congenital (AHC) boy. A boy aged five years and nine months initially examined for the primary adrenal insufficiency symptoms. Next-generation sequencing confirmed the X-linked inheritance of a novel stop-loss DAX1 variant: c.1411T>C/p.Ter471Gln associated with AHC in the patient. The patient was subjected to a brief clinical follow-up from 11 to 15.1 years of age. The effect of the mutant-DAX1 variant (p.Ter471Gln) on DAX1-steroidogenic factor 1 (SF1) (protein-protein) interaction was studied by protein-protein docking using the ClusPro-online tool. At 5.9 yrs of age, the patient exhibited precocious puberty with the secondary sexual characteristics of Tanner 2 stage (of 9-14 yrs of age). The patient showed primary adrenal insufficiency with diminished cortisol concentrations at blood serum (25 ng/ml) and urine (3.55 µg/24 h) levels. Upon steroidal exposure, the patient showed normalized serum cortisol levels of 45-61 ng/ml. However, the precocious puberty got prolonged with the increased penis length of 8.5 cm and the bone age of 18 yrs old during the follow-up. The patient showed increased basal serum adrenocorticotropic hormone (110->2000 pg/ml) and follicle-stimulating hormone (18.4-22.3 mIU/ml) concentrations. Following an elevated hypothalamic-pituitary-gonadal axis activity witnessed upon gonarellin stimulation. Protein-protein docking confirmed a weaker interaction between the mutant-DAX1 (p.Ter471Gln) protein and the wild-SF1 protein. Overall, we hypothesize the weakened mutant-DAX1-SF1 (protein-protein) interaction could govern the prolonged precocious puberty augmented with the elevated hypothalamic-pituitary-gonadal/adrenal axis responses via SF1-induced neuronal nitric oxide synthetase activation in the patient.

Clinical, Biochemical, Molecular, and Outcome Features of Mitochondrial 3-Hydroxy-3-Methylglutaryl-CoA Synthase Deficiency in 10 Chinese Patients.

Background: Mitochondrial 3-hydroxy-3-methylglutaryl-CoA synthase deficiency (HMGCS2D) is a rare autosomal recessive metabolic disorder caused by mutations of the HMGCS2 gene. To date, no more than 60 patients have been reported throughout the world. Purpose: To analyze the clinical, biochemical, molecular, and outcome features of HMGCS2D in a case series of 10 new Chinese patients. Methods: This retrospective study includes 10 Chinese patients diagnosed with HMGCS2D. We collected and analyzed clinical data for all patients. We also reviewed clinical data for 39 cases that had been reported previously. Results: All of our patients had experienced their first metabolic crisis before 12 months old. The most common clinical manifestations were anorexia, dyspnea, and disturbance of consciousness (10/10), followed by vomiting (8/10), fever (7/10), cough (4/10), diarrhea, and seizures (3/10). Each patient (10/10) had a different degree of hepatomegaly and increased aminotransferase, severe metabolic acidosis, and hypofibrinogenemia. 9 patients presented with severe hypoglycemia and weak positives on qualitative tests of urinary ketone body. Patient 3 was the only one without hypoglycemia. Five patients had hypocalcemia, five patients had hyperammonemia, four patients had hyperuricemia, and three had hypertriglyceridemia. During the metabolic acidosis episode, we observed high dicarboxylic acid values in urine, and the elevated ratio of blood acetylcarnitine to free carnitine may have been an additional biochemical signature. However, all returned to normal during the interictal interval. Molecular analysis identified 15 variants in the HMGCS2 gene, of which 10 were novel (c.220G>A/p.E74K, c.407A>G/p.D136G, c.422T>A/p.V141D, c.719A>C/p.D240A, c.821G>A/p.R274H, c.39dupA/p.L14Tfs*59, c.1394delA/p.N465Tfs*10, c.788delT/p.L263Cfs*36, c.717T>G/p.Y239*, and c.1017-2A>G). Combining these with previous cases, the known mutation c.1201G>T/p.E401* has been found in 6/40 (15.0%) of mutated alleles in 21 Chinese patients from 20 families, while none have been found in other populations. We found that patients with biallelic truncation mutation appeared to show a more severe clinical condition through a literature review. Conclusion: This study analyzed the phenotypic and genetic features of HMGCS2D in a Chinese case series. We also expanded the HMGCS2 mutational spectrum with 10 novel variants. The c.1201G>T/p.E401* mutation was the most frequent, representing 15.0% of the mutated alleles in reported unrelated Chinese patients, and thus, it may be a hot spot mutation.

A rare mutation c.1663G > A (p.A555T) in the MMUT gene associated with mild clinical and biochemical phenotypes of methylmalonic acidemia in 30 Chinese patients.

BACKGROUND: Methylmalonic acidemia is an inherited organic acid metabolic disease. It involves multiple physiological systems and has variable manifestations. The primary causative gene MMUT carries wide range of mutations, and one of them, c.1663G > A (p.A555T), is considered to be a rare type, which is seen more frequently in Asian than other populations. So far, little is known about the clinical features of patients carrying this mutation. In the present study, we aimed to define the clinical and biochemical features of the patients with this genotype. METHODS: Among 328 mut type methylmalonic acidemia patients from multiple hospitals in China, we collected 30 compound heterozygous patients sharing the mutation c.1663G > A (p.A555T) in the MMUT gene. Their clinical characteristics and biochemical index were described in detail and compared with methylmalonic acidemia patients without this variant. RESULTS: Most of these patients were diagnosed via newborn screening (26/30), treated in a timely manner, and kept healthy (24/30). Disease onset occurred in 7 patients. Developmental delay or intellectual impairment occurred in 4 patients. 100% of these patients (29/29) were responsive to Vitamin B12 administration. The blood propionylcarnitine, blood propionylcarnitine/acetylcarnitine ratio, urinary methylmalonic acid, urinary methylcitric acid before and after treatment in c.1663G > A (p.A555T) carrying patients were much lower than those in non-c.1663G > A (p.A555T) carrying patients. CONCLUSION: Compared to patients with other mutations in the MMUT gene, patients with the c.1663G > A (p.A555T) mutation showed later onset, milder clinical phenotype, lighter biochemical abnormalities, better vitamin B12 responsiveness, lower morbidity, easier metabolic control, and thereby better prognosis. Newborn screening project plays an important role in early diagnosis, treatment, and prognosis of these patients.

Different mutations in the MMUT gene are associated with the effect of vitamin B12 in a cohort of 266 Chinese patients with mut-type methylmalonic acidemia: A retrospective study.

BACKGROUND: To summarize the relationship between different MMUT gene mutations and the response to vitamin B12 in MMA. METHODS: This was a retrospective study of patients diagnosed with mut-type MMA. All patients with mut-type MMA were tested for responsiveness to vitamin B12. RESULTS: There were 81, 27, and 158 patients in the completely responsive, partially responsive, and nonresponsive groups, respectively, and the proportions of symptom occurrence were 30/81 (37.0%), 21/27 (77.8%), and 131/158 (82.9%), respectively (p < .001). The median levels of posttreatment propionyl carnitine (C3), C3/acetyl carnitine (C2) ratio in the blood, and methylmalonic acid in the urine were all lower than pretreatment, and the median level of C3/C2 ratio in the completely responsive group was within the normal range. In 266 patients, 144 different mutations in the MMUT gene were identified. Patients with the mutations of c.1663G>A, c.2080C>T, c.1880A>G, c.1208G>A, etc. were completely responsive and with the mutations of c.1741C>T, c.1630_1631GG>TA, c.599T>C, etc. were partially responsive. The proportions of healthy/developmental delay outcomes in the three groups were 63.0%/23.5%, 33.3%/40.7%, and 13.3%/60.1%, respectively (p < .001). CONCLUSION: Different mutations in the MMUT gene are associated with the effect of vitamin B12 treatment.