THEORY EXPLAINING ABNORMALITY IN 45,X-46,XY MOSAICISM WITH NON-FLUORESCENT Y-CHROMOSOME - PRESENTATION OF 3 CASES

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  • 1 January 1978
    • journal article
    • research article
    • Vol. 21  (1) , 5-11
Abstract
Three patients with male habitus, short stature and testicular differentiation are described. All had mos 45,X/46,XY, the ratio of the 2 stemlines varying between the patients and between different tissues. The Y chromosome was abnormal, lacking the brilliant QFQ [quinacrine bands by fluorescence using quinacrine and reverse banding by acridine orange] fluorescence and dark CGB [constitutive heterochromatin by giemsa using barium hydroxide] staining characteristic of the distal part of the normal Y. Detailed banding studies suggested that the short arm and proximal part of the long arm were normal, while the distal part of the long arm was molecularly or otherwise altered, resulting in abnormal staining properties. Two of the patients were tested for H[histocompatibility]-Y antigen and found to be positive. These data and those collected from the literature are compatible with a model in which the primary lesion in X/XY mosaicism is a molecular alteration in the reiterated Y-specific DNA sequences (and possibly neighboring sequences) of a 46,XY zygote resulting in the frequent mitotic loss of the Y and the emergence of a 45,X line. Provided the testis-determining gene(s) near the centromere are normal, testes are formed and the patient is H-Y antigen-positive. The extent of male or female differentiation depends in part on the prevalence, time of occurrence, and distribution of the 45,X line and possibly in part on the alteration of other genes involved in sex differentiation and located on Yq further from the centromere.