Variable phenotypes and outcomes associated with the MMACHC c.482G > A mutation: follow-up in a large CblC disease cohort.

BACKGROUND: The aim of this study was to characterize the variable phenotypes and outcomes associated with the methylmalonic aciduria and homocystinuria type C protein gene (MMACHC) c.482G > A mutation in 195 Chinese cases with CblC disease. METHODS: We carried out a national, retrospective multicenter study of 195 Chinese patients with CblC disease attributable to the MMACHC c.482G > A variant either in a homozygous or compound heterozygous state. The control group consisted of 200 patients diagnosed with CblC disease who did not possess the c.482G > A mutation. Clinical features, including disease onset, symptoms, biochemical metabolites, gene mutation, and follow-up outcomes were reviewed and analyzed in detail. The median follow-up period spanned 3 years and 8 months, with a range of 1 year and 2 months to 12 years and 10 months. RESULTS: Among 195 patients carrying the c.482G > A variant, 125 (64.1%) cases were diagnosed by newborn screening (NBS), 60 (30.8%) cases were detected due to disease onset, and 10 (5.1%) cases were identified from sibling diagnoses. One hundred and seventeen (93.6%) individuals who were diagnosed by NBS, and nine patients who came from sibling diagnoses remained asymptomatic in this study. From 69 symptomatic patients of the c.482G > A group, more patients presented with later onset, and the top six common clinical symptoms at disease onset were developmental delay (59.4%), lower limb weakness and poor exercise tolerance (50.7%), cognitive decline (37.7%), gait instability and abnormal posture (36.2%), seizures (26.1%), and psychiatric and behavioral disturbances (24.6%). In the 159 symptomatic patients lacking c.482G > A variants, the most frequently observed clinical manifestations at disease onset included developmental delay (81.8%), lethargy and feeding difficulty (62.9%), lower limb weakness and poor exercise tolerance (54.7%), prolonged neonatal jaundice (51.6%), vomiting (47.2%), and seizures (32.7%). Before treatment, the levels of blood propionylcarnitine, propionylcarnitine/acetylcarnitine ratio, and homocysteine in the c.482G > A group were significantly lower (P < 0.05) than those in the non-c.482G > A group, while the concentration of urinary methylmalonic acid was slightly lower (P > 0.05). The degree of decline in the above metabolites after treatment in different groups significantly differed in both plasma total homocysteine values and urinary methylmalonic acid levels (P < 0.05). In patients carrying the c.482G > A variant compared with the non-c.428G > A group, there were markedly lower rates of mortality (0.5% vs. 2.0%) and developmental delay (20.5% vs. 65.5%). When compared with individuals diagnosed due to disease onset, those identified through NBS in either group exhibited a reduced proportion of disease onset (6.7% vs. 100% in the c.482G > A group, 54.4% vs. 100% in the non-c.482G > A group), lower mortality (0.0% vs. 1.7% in the c.482G > A group, 0.0% vs. 3.6% in the non-c.482G > A group), and had a higher percentage of patients exhibiting normal psychomotor and language development (99.3% vs. 33.3% in the c.482G > A group, 58.9% vs. 10.9% in the non-c.482G > A group). CONCLUSIONS: The c.482G > A variant in MMACHC is associated with late-onset and milder phenotypes of CblC disease. Patients with this mutation tend to have a relatively better response to hydroxocobalamin, better metabolic control, and more favorable neurological outcomes. NBS and other appropriate pre-symptomatic treatments seem to be helpful in early diagnosis, resulting in favorable clinical outcomes. Video Abstract (MP4 136794 kb).

Diagnosis and therapeutic monitoring of inborn errors of metabolism in 100,077 newborns from Jining city in China.

BACKGROUND: Mandatory newborn screening for metabolic disorders has not been implemented in most parts of China. Newborn mortality and morbidity could be markedly reduced by early diagnosis and treatment of inborn errors of metabolism (IEM). Methods of screening for IEM by tandem mass spectrometry (MS/MS) have been developed, and their advantages include rapid testing, high sensitivity, high specificity, high throughput, and low sample volume (a single dried blood spot). METHODS: Dried blood spots of 100,077 newborns obtained from Jining city in 2014-2015 were screened by MS/MS. The screening results were further confirmed by clinical symptoms and biochemical analysis in combination with the detection of neonatal deficiency in organic acid, amino acid, or fatty acid metabolism and DNA analysis. RESULTS: The percentages of males and females among the 100,077 infants were 54.1% and 45.9%, respectively. Cut-off values were established by utilizing the percentile method. The screening results showed that 98,764 newborns were healthy, and 56 out of the 1313 newborns with suspected IEM were ultimately diagnosed with IEM. Among these 56 newborns, 19 (1:5267) had amino acid metabolism disorders, 26 (1:3849) had organic acid metabolism disorders, and 11 (1:9098) had fatty acid oxidation disorders. In addition, 54 patients with IEM were found to carry mutations, and the other 2 patients had argininemia. CONCLUSIONS: Fifty-six cases of metabolic disorders in Jining were confirmed via newborn screening (NBS) by MS/MS. Early diagnosis and treatment are crucial for the survival and well-being of affected children. A nationwide NBS program using MS/MS is recommended, especially in poor areas of China.

[Study on manufacturing materials of imitation snails].

OBJECTIVE: To make imitation snails by using substances with chemotaxis to Schistosoma japonicum miracidia. METHODS: The imitation snails were made by using Fe3+, gelatin and agar. The modified comparison method of Roberts was used to observe the chemotaxis of imitation snails and snail conditioned water (SCW) to Schistosoma japonicum miracidia. RESULTS: The mixture consisting of 0.1 or 0.5 mol/L Fe3+, 9% or 10% gelatin, and that consisting of 0.5 mol/L Fe3+, 9% gelatin, 2% or 1% agar could be used to make the imitation snails. The chemotaxis of imitation snails made by the mixtures above was stronger than that of SCW. CONCLUSION: The mixtures made by certain proportion of Fe3+, gelatin or gelatin and agar can be used to make imitation snails.