The family observed in this study included affected males and asymptomatic females. The patients shared specific digital abnormalities including postaxial polydactyly, cutaneous syndactyly, and brachydactyly. In addition, the patients exhibited mild-to-moderate intellectual disability and short stature coupled with microbrachycephaly, scoliosis, and cerebellar and renal hypoplasia. No chromosomal alterations or copy number variations were found in the index case. The genetic linkage analysis, which focused on the X chromosome, and the haplotype analysis detected a ~15.74 Mb candidate region located at Xp11.4-p11.21 with a LOD score of 4.8. Additionally, half of the mothers showed skewed X-inactivation, while the other mothers exhibited random inactivation patterns. The candidate region includes 28 protein-encoding genes that have not yet been implicated in human disorders. We speculate that the observed phenotype is compatible with a monogenic disorder in which the mutant gene plays a significant role during embryonic development. Based on the patients' clinical features, image studies, pedigree, chromosome location, and X-inactivation studies in the mothers, we propose that this family has a novel, specific syndrome with an X-linked recessive mode of inheritance.
Mutations in the Emopamil-binding protein (EBP) gene cause X-linked dominant chondrodysplasia punctata 2 (CDPX2), a disorder in which at least 95% of liveborn individuals are female and male intrauterine lethality is assumed. Several affected males with mutations in EBP have been reported. These males exhibit a phenotype similar to CDPX2 due to either somatic mosaicism or a 47, XXY karyotype in association with a null EBP allele. Alternatively, affected males may exhibit a distinct phenotype if they are hemizygous for a hypomorphic allele of EBP. Recently, we described a novel X-linked phenotype associated with digital abnormalities, intellectual disability and short stature, and mapped it to Xp11.4-p11.21. X-exome sequencing was performed to identify the mutated gene responsible for this phenotype. A novel missense variant, c.224T>A (p.I75N), was identified in EBP. SIFT and PolyPhen-2 predicted this change to be deleterious. The pathogenicity of this variant was subsequently supported by increased plasma levels of 8(9)-cholestenol in the proband and his mother. The molecular and biochemical evidence convincingly supports the pathogenicity and association of the p.I75N mutation with this newly described phenotype. This study expands the current phenotypic spectrum of males with hypomorphic EBP mutations and supports to the hypothesis that there exists an X-linked recessive entity independent of CDPX2.
The HPV prevalence was 20.1% in the present study; the most prevalent infections were HPV-59, HPV-52, HPV-16, and HPV-56. At 3-year follow-up, 25 (19.4%) patients had HPV infections.
This report is the first to suggest an association between HPV-2 and pyogenic granuloma. This relationship is similar to that observed between HPV-2 and nongenital warts.
Background
Male EBP disorder with neurologic defects (MEND) syndrome is an X‐linked disease caused by hypomorphic mutations in the EBP (emopamil‐binding protein) gene. Modifier genes may explain the clinical variability among individuals who share a primary mutation.
Methods
We studied four males (Patient 1 to Patient 4) exhibiting a descending degree of phenotypic severity from a family with MEND syndrome. To identify candidate modifier genes that explain the phenotypic variability, variants of homeostasis cholesterol genes identified by whole‐exome sequencing (WES) were ranked according to the predicted magnitude of their effect through an in‐house scoring system.
Results
Twenty‐seven from 105 missense variants found in 45 genes of the four exomes were considered significant (−5 to −9 scores). We found a direct genotype–phenotype association based on the differential accumulation of potentially functional gene variants among males. Patient 1 exhibited 17 variants, both Patients 2 and 3 exhibited nine variants, and Patient 4 exhibited only five variants.
Conclusion
We conclude that APOA5 (rs3135506), ABCA1 (rs9282541), and APOB (rs679899 and rs12714225) are the most relevant candidate modifier genes in this family. Relative accumulation of the deficiencies associated with variants of these genes along with other lesser deficiencies in other genes appears to explain the variable expressivity in MEND syndrome.
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