Cryptic duplication of the distal segment of 22q due to a translocation (21;22): three case reports and a review of the literature.

Duplications of the proximal segment of chromosome 22q are not uncommon, like Cat-eye syndrome and duplications due to familial (11;22) translocations. However, duplications of the distal long arm of chromosome 22 (22qter) seem to be exceedingly rare. So far, duplications of 22q12 or 22q13 to 22qter have been described in 21 patients, of whom 13 had a pure duplication 22qter. Here we report on three new cases with a pure duplication of the distal part of 22q. The first patient carries a duplication of terminal 22q due to a de novo unbalanced translocation, 46,XX,der(21)t(21;22) (p13;q13.2), detected by NOR-staining, while the other patients have a familial cryptic duplication of terminal 22q due to an unbalanced translocation, 46,XY,der(21)t(21;22)(p10;q13.3). The last two patients were initially thought to have a polymorphic variant of 21p, but additional subtelomeric screening using FISH showed the extra material was derived from chromosome 22. Terminal duplications of 22qter may be more common than generally assumed, but due to its small size, especially when located on an acrocentric chromosome and/or possibly relatively mild phenotype remain undetected thus far.

A new case of dup(1)(q21.2q12) in an individual with mild mental retardation.

Proximal duplications of the long arm of chromosome 1 are rare and the few patients that have been described in literature have multiple congenital abnormalities and/or mental retardation. The present paper describes the clinical and cytogenetic findings of an adult patient with only mild mental retardation and some minor malformations. The patient carries an inverted duplication of 1q12q21.2.

Dysmorphology and mental retardation: molecular cytogenetic studies in dysmorphic mentally retarded patients.

In an institutionalised population of 471 mentally retarded adult residents (436 males and 35 females), 18 patients (16 males and 2 females) with dysmorphic features were selected to perform FISH studies by using subtelomeric probes to discover cryptic terminal deletions or duplications, undetectable with standard banding techniques. In the 13 investigated patients, no abnormalities were found with a selected battery of subtelomeric probes. The results of cryptic chromosomal rearrangement studies are variable but the frequency of positive diagnostic findings seems to be lower than previously expected.

Identification of an unbalanced cryptic translocation between the chromosomes 8 and 13 in two sisters with mild mental retardation accompanied by mild dysmorphic features.

Recently, much attention has been given to subtelomeric chromosomal rearrangements as important aetiological factors leading to idiopathic mental retardation. However, detection of these aberrations is difficult, mostly due to technical limitations and lack of genotype-phenotype relationships. We report on a family with a history suggestive of segregation of a chromosomal anomaly. In two mildly mentally retarded sisters with a similar phenotype consisting of obesitas, skin atrophy of the lower limbs and mild facial dysmorphisms, a subtle unbalanced cryptic translocation (46,XX,der(13)t(8;13)(q24.3;q34)) was detected on routine cytogenetic investigation followed by additional FISH studies. The translocation originated from the mother.

Down-Turner syndrome: case report and review.

We present a male patient with Down-Turner mosaicism (45,X/46,X,+21/47,XY,+21) and review 27 similar cases reported so far. Clinical features of Down's syndrome were present in all cases, whereas a combination of features of both Ullrich-Turner syndrome and Down's syndrome was reported in 61% of the patients. However, one has to bear in mind that several stigmata of Ullrich-Turner syndrome can also be present in patients with Down's syndrome and vice versa. In most of the patients two different cell lines were encountered, although cases with one, three, and even four different cell lines have been reported. Of 28 patients, 21 showed female external genitalia, four were phenotypically male, and three showed ambiguous genitalia. Only six patients (21%) carried a Y chromosome, which is far less than expected.