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An unusual fragile X sibship: female compound heterozygote and male with a partially methylated full mutation
Author(s) -
Russo S.,
Briscioli V.,
Cogliati F.,
Macchi M.,
Lalatta F.,
Larizza L.
Publication year - 1998
Publication title -
clinical genetics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.543
H-Index - 102
eISSN - 1399-0004
pISSN - 0009-9163
DOI - 10.1034/j.1399-0004.1998.5440408.x
Subject(s) - brother , sister , wechsler adult intelligence scale , genetics , mutation , compound heterozygosity , psychology , biology , cognition , psychiatry , gene , sociology , anthropology
We describe here a fragile X sibship of borderline retarded sister and brother born to carrier parents. The sister is a compound heterozygote (with a full mutation on one X chromosome and a pre‐mutation on the other X chromosome). The brother has a partially methylated full mutation. The activation ratio (AR) for the sister's pre‐mutation was 0.69 and the percent lack of methylation for the brother's full mutation was 73%. Intellectual and neuropsychological Wechsler Adult Intelligence Scale (W.A.I.S.) achievement tests reported full scale IQ scores of 74 in the sister and 77 in the brother. A significant discrepancy between verbal and performance IQ was found in the sister, indicating that her main impairment was in the cognitive area. The parents of this unusual sibship came from a small village, as did one of the two previously described cases of compound heterozygous females. These rare females raise special issues for genetic counselling in fragile X carrier couples, the frequency of which remains to be defined in different populations.