ABSTRACT
5α-Reductase type 2 deficiency causes a 46,XY disorder of sex development (DSD) characterized by ambiguous external genitalia, rudimentary prostate, and normal internal genitalia. The disease prevalence worldwide is low, but in a small and isolated village of the Venezuelan Andes, a higher incidence has been found. DNA analysis of the SRD5A2 gene was performed in three inbred affected individuals clinically diagnosed with DSD. The entire coding regions, the p.L89V polymorphism (rs523349) and five intragenic SNPs (rs2300702, rs2268797, rs2268796, rs4952220, rs12470196) used to construct haplotypes were analyzed by Sanger sequencing. To assess the probable ethnic origin of the mutation in this geographic isolate, a population structure analysis was performed. Homozygosis for the p.N193S mutation was found in all patients, with a mutation carrier frequency of 1:80 chromosomes (0.0125) in the geographic focus, suggesting a founder phenomenon. The results of the population structure analysis suggested a mutation origin closer to the Spanish populations, according to the clusters grouping. The genotype-phenotype correlation in the patients was not absolute, being hypospadias and cryptorchidism the main traits that differentiate affected individuals.
Subject(s)
3-Oxo-5-alpha-Steroid 4-Dehydrogenase/genetics , Disorder of Sex Development, 46,XY/genetics , Membrane Proteins/genetics , Mutation , Polymorphism, Genetic , 3-Oxo-5-alpha-Steroid 4-Dehydrogenase/deficiency , Adolescent , Case-Control Studies , Child , Disorder of Sex Development, 46,XY/enzymology , Disorder of Sex Development, 46,XY/epidemiology , Disorder of Sex Development, 46,XY/pathology , Female , Humans , Infant , Male , Membrane Proteins/deficiency , Phenotype , Prognosis , Venezuela/epidemiologyABSTRACT
Amniotic Band Syndrome is a sporadic condition with a spectrum of clinical presentations that include constriction rings, pseudosyndactily, amputations, multiple craniofacial - visceral - body wall defects and spontaneous abortion. The incidence ranges from 1: 1 200 to 1: 15 000 newborns, creating controversy regarding its pathogenesis. We report 3 cases with different clinical manifestations of this entity and review the different etiological hypotheses for this syndrome. Two main pathogenic mechanisms are proposed: the exogenous theory with early amnion rupture leading to fibrous bands that entrap the fetal body and the endogenous theory that establishes a germ plasm defect with vascular disruption and disturbance of morphogenesis during early gastrulation. However, the exact etiology of Amniotic Band Syndrome remains unknown and its natural evolution is unpredictable. The observed geographic difference in birth prevalence is useful in studying specific genetic and environmental factors involved. The management of this disease must be multidisciplinary and the outcome depends on malformations severity.
El síndrome de bridas amnióticas es una condición esporádica variable que presenta un espectro que incluye anillos de constricción, pseudosindactilia, amputaciones, múltiples alteraciones craneofaciales, viscerales, de la pared corporal y abortos espontáneos. El rango de incidencia es de 1 en 1 200 a 1 en 15 000 recién nacidos vivos. La patogenia del síndrome de bridas amnioticas es controversial. En el siguiente informe se reportan tres casos donde se describen las diferentes manifestaciones clínicas de esta entidad, además se revisaron las diferentes hipótesis etiológicas. Entre los dos mecanismos propuestos destacan la ruptura prematura del amnios (teoría exógena), que conlleva a la formación de bandas fibrosas que afectan el cuerpo fetal y la teoría endógena como defecto germinal, disrupción vascular y alteraciones en la morfogénesis durante la gastrulación temprana. Sin embargo, la etiología exacta del síndrome de bridas amnioticas es incierta y su curso natural es impredecible. Las diferencias geográficas observadas en las prevalencias de nacimiento puede ser una indicación útil para estudios de factores genéticos y ambientales candidatos. El manejo debe ser multidisciplinario y el pronóstico depende de la gravedad de las malformaciones.
