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Mental retardation unassociated with the Fragile X syndrome accounts for up to 60% of patients with X-linked mental retardation. In this investigation, we report on a family with mild non-specific X-linked mental retardation (MRX) without other apparent phenotypic abnormalities. Linkage analysis on 27 relatives using 18 polymorphic markers spanning the X-chromosome demonstrated close linkage to DXYS1 with a peak LOD score of 2.14 at a theta of 0. Numerous families with various types of MRX have now been studied by other investigators using molecular genetic techniques. In addition to the family described in this report, a number of these have demonstrated linkage to the DXYS1 locus. These data suggest that a gene for mental retardation may exist in the region of DXYS1. Alternatively, this area of the X-chromosome may harbor multiple different but closely linked genes which cause the various types of MRX.

An Austrian family with nonsyndromic X-linked mental retardation (MRX) is reported in which the obligatory carrier females are normal, and 5 affected males have mild to moderate mental retardation. Linkage analysis indicated an X pericentromeric localization, with flanking markers DXS989 and DXS1111 and a maximum multipoint LOD score of 2.09 (θ = 0) for the 7 cosegregating markers DXS1243, CybB, MAOB, DXS988, ALAS2, DXS991, and AR. MRX58 thus mapped within a 50-cM interval between Xp11.3 and Xq13.1 and overlapped with 23 other MRX families already described. This pericentromeric clustering of MRX families suggests allelism, with a minimum of 2 X-linked mental retardation (XLMR) genes in this region. Am. J. Med. Genet. 86:102–106, 1999. © 1999 Wiley-Liss, Inc.

Most structural congenital heart defects (CHD) are thought to be multifactorially determined, but the precise causal factors usually are unknown. One may postulate that vascular events, such as hemorrhage in the developing embryo, could influence morphogenesis of the heart. One method of studying this hypothesis is to determine the frequency of CHD in persons with heritable bleeding diatheses and their families. We reviewed retrospectively medical and family histories of 120 hemophilia A and 14 hemophilia B patients seen in our Genetics Department. The family histories included 1, 126 maternal relatives of hemophiliac patients. We also reviewed the family histories of 138 patients with X-linked disorders who did not have bleeding diatheses or syndromes associated with CHD; these histories included 960 maternal relatives. There was one confirmed case of a CHD in 134 hemophilia patients, giving a frequency of 0.75% compared to 0.8% in the general population at birth. There was no apparent difference in the frequency of CHD in hemophilia A and B patients compared to the general population or in the relatives of hemophilia patients as compared to control individuals.

Urticaria in response to various physical stimuli has been reported in sporadic and familial patterns. The most common of these physical urticarias, dermographism, is a localized urticarial response to stroking or scratching of the skin and has not been reported previously to be familial. A four-generation family with dermographism, probably inherited as an autosomal dominant trait, is presented along with a discussion of sporadic dermographism and other types of familial physical urticarias.