TY - JOUR T1 - Clinical and cytogenetic characterisation of a patient with Down syndrome resulting from a 21q22.1→qter duplication JF - Journal of Medical Genetics JO - J Med Genet SP - 73 LP - 76 DO - 10.1136/jmg.38.1.73 VL - 38 IS - 1 AU - MARGA NADAL AU - CÉSAR GUZMÁN VIGO AU - MARIA ISABEL MELARAGNO AU - JOYCE A D ANDRADE AU - LUIS GARCIA ALONSO AU - DECIO BRUNONI AU - MELANIE PRITCHARD AU - XAVIER ESTIVILL Y1 - 2001/01/01 UR - http://jmg.bmj.com/content/38/1/73.abstract N2 - Editor—Trisomy of human chromosome 21 is one of the most frequent aneuploidies in humans and results in Down syndrome (DS), affecting approximately 1 in 700 live births.1 DS is a major cause of mental retardation and congenital heart disease in humans, but is also associated with other major features, such as characteristic facies, skeletal abnormalities, and an increased risk of leukaemia and Alzheimer's disease. In most cases (95%), the trisomy of chromosome 21 involves the whole chromosome through maternal (most frequent) or paternal non-disjunction, whereas in some cases (4%) Down syndrome is the result of an unbalanced translocation. Among the latter, a very small proportion of cases are the result of partial trisomy of chromosome 21 arising either from non-Robertsonian translocations or from intrachromosomal duplications.2 The DS phenotype is also found in cases (1%) of mosaicism of trisomy 21.3 During the last decade, considerable progress has been made towards discovering the gene content of chromosome 21, but the functions of most of these genes and their specific contributions to the final DS phenotype still remain unknown. The identification and characterisation of cases of partial trisomy of chromosome 21 has allowed a phenotypic map of this chromosome and DS to be constructed. Clinical and molecular studies of these cases have suggested that most of the phenotypic features of DS are the result of the triple dose of the genes contained in the region around marker D21S55. This region is called the Down syndrome critical region (DSCR).4-6 However, recent evidence suggests that genes outside this region may also contribute to the DS phenotype.7 To evaluate DS patients clinically, a checklist of 25 clinical traits was first reported by Jacksonet al 8 and later revised by Epstein et al.9 The accurate and exhaustive … ER -