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A History of Mental Retardation
Published in Merlin G. Butler, F. John Meaney, Genetics of Developmental Disabilities, 2019
Giovanni Neri, Francesco D. Tiziano
An account of the modern history of X-linked mental retardation (XLMR), although brief, deserves a place within a general history of mental retardation. It has been known for quite some time that there is an excess of males among the mentally retarded. In 1938, Penrose published his famous Colchester Survey (52), a milestone in the history of mental retardation, showing a 20% excess of males in a hospital sample of 1280 mentally retarded individuals. He attributed this unexpected observation to ascertainment bias, demonstrating that even the great Penrose could be mistaken, as we shall see in a moment. Again, 25 years later, he wrote in The Biology of Mental Defect that “… in general, the genes on the X chromosome do not play any greater part in the causation of mental defect than might be supposed from the fact that there are 22 autosomes to one sex chromosome in man… The conclusion may be drawn that there is no outstanding tendency for sex-linked genes to influence the genetics of mental deficiency” (53, p. 127). The statement is more surprising if one considers that at that time Penrose must have been aware of several maternally transmitted XLMR conditions, including the Martin–Bell syndrome (54), which is now considered the archetype of XLMR. Martin and Bell’s report of 1943 is of historical value per se and also for the demonstration, almost 40 years later, that surviving members of the family were positive for the fragile X test (55), proving beyond doubt that the Martin–Bell and the fragile X syndrome are one and the same condition. Other families of historical value are described by Allan et al. (56), whose affected members were known as the “limbernecks” of rural North Carolina, and that described by Dr. Renpenning when he was a medical student at the University of Saskatchewan (57). Curiously, the Renpenning syndrome, which is distinctively characterized by microcephaly and short stature, was considered for a period of time the prototype of XLMR, and, as such, confused with the Martin–Bell syndrome, usually characterized by macrocephaly and tall stature.
Microphthalmos-anophthalmos-coloboma (MAC) spectrum in two brothers with Renpenning syndrome due to a truncating mutation in the polyglutamine tract binding protein 1 (PQBP1) gene
Published in Ophthalmic Genetics, 2019
Maha M. Mameesh, Adila Al-Kindy, Majda Al-Yahyai, Anuradha Ganesh
The polyglutamine-binding protein 1 (PQBP1) maps to chromosome Xp11.23. Mutations in this gene have been implicated in patients with syndromic and non-syndromic X-linked intellectual disabilities collectively referred to as Renpenning syndrome (MIM # 309500). Renpenning syndrome is a rare disorder with a prevalence of <1/1000000 (5). Clinical manifestations are heterogenous including variable intellectual disability, primary microcephaly, mild postnatal growth deficiency and hypogonadism. Other less common features include dysmorphic facies, spasticity, muscle atrophy, cleft palate, cardiac and anorectal malformations (6). While ocular malformation has been reported in Renpenning syndrome, there is a lack of comprehensive description (6).