Identification of Novel and Recurrent RMRP Variants in a Series of Brazilian Patients with Cartilage-Hair Hypoplasia: McKusick Syndrome.

Cartilage-hair hypoplasia syndrome (CHH) is an autosomal recessive disorder caused by pathogenic variants of the RMRP gene and characterized by metaphyseal bone dysplasia associated with hypotrichosis, immunodeficiency, and predisposition to malignancy. However, the genotype-phenotype correlation in CHH is not well understood. Here, we report a single country cohort of 23 Brazilian patients with clinical and radiological features consistent with CHH. We found 23 different pathogenic variants in the RMRP gene - 12 novel and 11 previously described in the literature. Interestingly, the most frequent Finnish pathogenic variant related to CHH (g.71A>G) was not found in our cohort. In contrast, more than 50% of the patients carried the rare g.196C>T variant suggesting a possible founder effect in the Brazilian population. In silico analysis showed that pathogenic variants occurred either in the regions conserved in mammalian species or within essential domains for the ribonucleoprotein complex. Pathogenicity prediction studies can improve the understanding of how these variants affect RNA.

A rapid and accurate methylation-sensitive high-resolution melting analysis assay for the diagnosis of Prader Willi and Angelman patients.

BACKGROUND: Prader Willi (PWS) and Angelman (AS) syndromes are rare genetic disorders characterized by deletions, uniparental disomy, and imprinting defects at chromosome 15. The loss of function of specific genes caused by genetic alterations in paternal allele causes PWS while the absence in maternal allele results AS. The laboratory diagnosis of PWS and AS is complex and demands molecular biology and cytogenetics techniques to identify the genetic mechanism related to the development of the disease. The DNA methylation analysis in chromosome 15 at the SNURF-SNRPN locus through MS-PCR confirms the diagnosis and distinguishes between PWS and AS. Our study aimed to establish the MS-PCR technique associated with High-Resolution Melting (MS-HRM) in PWS and AS diagnostic with a single pair of primers. METHODS: We collected blood samples from 43 suspected patients to a cytogenetic and methylation analysis. The extracted DNA was treated with bisulfite to perform comparative methylation analysis. RESULTS: MS-HRM and MS-PCR agreed in 100% of cases, identifying 19(44%) PWS, 3(7%) AS, and 21(49%) Normal. FISH analysis detected four cases of PWS caused by deletions in chromosome 15. CONCLUSION: The MS-HRM showed good performance with a unique pair of primers, dispensing electrophoresis gel analysis, offering a quick and reproducible diagnostic.

Clinical characteristics of alopecia areata in Down syndrome.

This study was undertaken to better understand clinical characteristics, environmental and physical events in Down syndrome (DS) and alopecia areata (AA). This cross-sectional study included 18 DS patients who were currently presenting or had presented AA. We evaluated gender, age, location and type of AA, presence of autoimmune disease or atopy, AA in first-degree relatives, and environmental, physical, and clinical intercurrences. The mean age of study subjects was 11.6 (SD ± 5.5) years and mean age at AA onset 7.2 (2.5 to 15.2) years. The duration of alopecia episodes varied, with a mean of 2.7 (0.1 to 18.7) years. Recurrence of AA was reported in 27.7% (5/18) of subjects, with a mean number of recurrences of 3.6. Localized type AA was seen in 83.4% of individuals, with the most frequent location on the scalp (100%). Seven of the individuals presented atopy. Fourteen individuals had undergone environmental and/or clinical intercurrences. In conclusion, the most frequent presentation of AA in DS is the non-recurrent, localized form on the scalp, with a varied period of duration. Changes in the individuals' routine occurred in more than half of the study group. We suggest further studies of the psychology and immunogenetics in the etiopathology of AA in DS.