Phenotypic variability to medication management: an update on fragile X syndrome

This review discusses the discovery, epidemiology, pathophysiology, genetic etiology, molecular diagnosis, and medication-based management of fragile X syndrome (FXS). It also highlights the syndrome's variable expressivity and common comorbid and overlapping conditions. FXS is an X-linked dominant disorder associated with a wide spectrum of clinical features, including but not limited to intellectual disability, autism spectrum disorder, language deficits, macroorchidism, seizures, and anxiety. Its prevalence in the general population is approximately 1 in 5000-7000 men and 1 in 4000-6000 women worldwide. FXS is associated with the fragile X messenger ribonucleoprotein 1 (FMR1) gene located at locus Xq27.3 and encodes the fragile X messenger ribonucleoprotein (FMRP). Most individuals with FXS have an FMR1 allele with > 200 CGG repeats (full mutation) and hypermethylation of the CpG island proximal to the repeats, which silences the gene's promoter. Some individuals have mosaicism in the size of the CGG repeats or in hypermethylation of the CpG island, both produce some FMRP and give rise to milder cognitive and behavioral deficits than in non-mosaic individuals with FXS. As in several monogenic disorders, modifier genes influence the penetrance of FMR1 mutations and FXS's variable expressivity by regulating the pathophysiological mechanisms related to the syndrome's behavioral features. Although there is no cure for FXS, prenatal molecular diagnostic testing is recommended to facilitate early diagnosis. Pharmacologic agents can reduce some behavioral features of FXS, and researchers are investigating whether gene editing can be used to demethylate the FMR1 promoter region to improve patient outcomes. Moreover, clustered regularly interspaced palindromic repeats (CRISPR)/Cas9 and developed nuclease defective Cas9 (dCas9) strategies have promised options of genome editing in gain-of-function mutations to rewrite new genetic information into a specified DNA site, are also being studied.

Variations in TAP1 and PSMB9 Genes Involved in Antigen Processing and Presentation Increase the Risk of Vitiligo in the Saudi Community

Background

The antigen processing 1 (TAP1) and proteasome 20S subunit beta 9 (PSMB9) genes are associated with strong susceptibility to many autoimmune diseases. Here, we explored whether TAP1/PSMB9 genetic variants, individually or combined, affected susceptibility to the complex, autoimmune-based skin disorder vitiligo.

Methods

Samples of genomic DNA from buccal cells of 172 patients with vitiligo and 129 healthy controls were analyzed using TaqMan™ genotyping assays for the TAP1 rs1135216 (A>G) and PSMB9 rs17587 (A>G) single nucleotide polymorphisms (SNPs). SNPStats software (https://www.snpstats.net) was utilized to choose the best interactive inheritance mode for selected SNPs.

Results

The genotype frequencies for the TAP1 rs1135216 and PSMB9 rs17587 SNPs were in Hardy-Weinberg equilibrium for cases (P= 0.11 and P= 0.10, respectively) but not for controls (P< 0.05). The TAP1 rs1135216 (D637G) and PSMB9 rs17587 (R60H) SNPs increased the risk of vitiligo four-fold and two-fold, respectively (odds ratio [OR]= 4.6; 95% confidence interval [CI], 3.2-6.5; P< 0.0001 and OR= 2.2; 95% CI, 1.5-3.1; P< 0.0001). The recessive model (G/G-D/G versus D/D) and the codominant model (R/R versus R/H) were the best models of inheritance for the rs113526 and rs17587 SNPs, respectively (OR= 16.4; 95% CI, 2.0-138; P= 0.0006 and OR= 1.7; 95% CI, 0.3-1.8; P= 0.013). Vulgaris, focal vulgaris, and acryl/acrofacial were the most common vitiligo subtypes in our sample (51%, 21%, and 19%, respectively). Heterozygous rs113526 (637D/G) and rs17587 (60R/H) were the most common genotypes in most vitiligo subtypes. The heterozygous 637D/G genotype and the 637G variant allele were significantly more common in patients with active disease than in patients with stable disease (P= 0.000052 and P= 0.0063, respectively).

Conclusion

Our findings suggest a crucial role for TAP1 rs1135216 and PSMB9 rs17587 in the risk and progression of vitiligo in the Saudi community. Genomic analyses are needed to identify more candidate genes and more genetic variants associated with vitiligo.

Variations in TAP1 and PSMB9 Genes Involved in Antigen Processing and Presentation Increase the Risk of Vitiligo in the Saudi Community

BACKGROUND

The antigen processing 1 (TAP1) and proteasome 20S subunit beta 9 (PSMB9) genes are associated with strong susceptibility to many autoimmune diseases. Here, we explored whether TAP1/PSMB9 genetic variants, individually or combined, affected susceptibility to the complex, autoimmune-based skin disorder vitiligo.

METHODS

Samples of genomic DNA from buccal cells of 172 patients with vitiligo and 129 healthy controls were analyzed using TaqMan™ genotyping assays for the TAP1 rs1135216 (A>G) and PSMB9 rs17587 (A>G) single nucleotide polymorphisms (SNPs). SNPStats software (https://www.snpstats.net) was utilized to choose the best interactive inheritance mode for selected SNPs.

RESULTS

The genotype frequencies for the TAP1 rs1135216 and PSMB9 rs17587 SNPs were in Hardy-Weinberg equilibrium for cases (P= 0.11 and P= 0.10, respectively) but not for controls (P< 0.05). The TAP1 rs1135216 (D637G) and PSMB9 rs17587 (R60H) SNPs increased the risk of vitiligo four-fold and two-fold, respectively (odds ratio [OR]= 4.6; 95% confidence interval [CI], 3.2-6.5; P< 0.0001 and OR= 2.2; 95% CI, 1.5-3.1; P< 0.0001). The recessive model (G/G-D/G versus D/D) and the codominant model (R/R versus R/H) were the best models of inheritance for the rs113526 and rs17587 SNPs, respectively (OR= 16.4; 95% CI, 2.0-138; P= 0.0006 and OR= 1.7; 95% CI, 0.3-1.8; P= 0.013). Vulgaris, focal vulgaris, and acryl/acrofacial were the most common vitiligo subtypes in our sample (51%, 21%, and 19%, respectively). Heterozygous rs113526 (637D/G) and rs17587 (60R/H) were the most common genotypes in most vitiligo subtypes. The heterozygous 637D/G genotype and the 637G variant allele were significantly more common in patients with active disease than in patients with stable disease (P= 0.000052 and P= 0.0063, respectively).

CONCLUSION

Our findings suggest a crucial role for TAP1 rs1135216 and PSMB9 rs17587 in the risk and progression of vitiligo in the Saudi community. Genomic analyses are needed to identify more candidate genes and more genetic variants associated with vitiligo.

A unique case of segmental vasal atresia

We report a case of a 2-year-old boy who presented with an empty left scrotum. Clinical examination revealed a left palpable undescended testis. During orchidopexy, segmental atresia of the vas deferens was found, and microsurgical repair was carried out. Segmental vasal atresia is an extremely rare condition and is infrequently diagnosed, especially in the pediatric age group. This is the first reported case of segmental vasal atresia without an association with cystic fibrosis.