ABSTRACT
We report on a sibship with one brother and two MZ twin sisters affected with osteoporosis-pseudoglioma syndrome. An analysis of the present and literature data showed that vitreoretinal dysplasia or phthisis bulbi and X-ray evidence of osteoporosis must be considered minimal diagnostic criteria. Mental retardation, ligamentous laxity, and other reported anomalies are highly variable manifestations in the syndrome. Segregation analysis confirmed autosomal recessive transmission. The geographic origin of reported families suggests a higher gene frequency in Mediterranean countries.
Subject(s)
Eye Abnormalities , Osteoporosis/genetics , Adult , Diseases in Twins , Female , Genes, Recessive , Growth Disorders/genetics , Humans , Male , Musculoskeletal System/pathology , Osteoporosis/diagnosis , Osteoporosis/diagnostic imaging , Pedigree , Radiography , Syndrome , Twins, MonozygoticABSTRACT
A case is reported of monozygotic triplets, discordant for phenotypic sex, in which the female presented at birth with the features of Turner's syndrome. Chromosomal analyses showed homogeneous 46,XY karyotypes in the lymphocytes of the three sibs, while a 45,X non-mosaic chromosome constitution was detected in skin fibroblasts of the female triplet. It is suggested that mitotic non-disjunction or anaphase lag occurring early during embryonic development accounted for the occurrence of monosomy X in one cell line of the affected triplet. Previous observations of monozygotic twin pairs discordant for chromosome constitutions are reviewed.
Subject(s)
Triplets , Turner Syndrome/genetics , X Chromosome , Blood Grouping and Crossmatching , Dermatoglyphics , Female , Fibroblasts/ultrastructure , Genetic Markers , Humans , Infant, Newborn , Karyotyping , Lymphocytes/ultrastructure , Male , Monosomy , Mosaicism , Nondisjunction, Genetic , Phenotype , PregnancyABSTRACT
The existence of a rare autosomal gene which in the homozygous state would cause mitotic nondisjunction in the Down zygote has been hypothesized in the past by Alfi et al. (1980). This hypothesis can be supported or contradicted by the study of the frequency of consanguineous marriages among parents of affected children. Our study on 242 children affected with Down syndrome does not show any increase in the frequency of consanguineous marriages among their parents with respect to the general population, and therefore does not support the hypothesis of an autosomal gene controlling mitotic nondisjunction. Our data do not show any increase in the frequency of consanguineous marriages even among paternal and maternal grandparents of the affected children, thus not supporting the other possible explanation of an autosomal recessive condition in one of the patient's parents which would cause meiotic nondisjunction.
