Chromosome analysis of blood cells from a 42-year-old white male with mental retardation, colon carcinoma, horseshoe kidney, absence of left lobe of the liver, agenesis of the gallbladder, and possible Gardner syndrome revealed a constitutional marker chromosome due to del(5)(q13q15) or del(5)(q15q22). A polymorphic chromosome #22 with enlarged satellites was inherited from the father, who is phenotypically normal, and was probably unrelated to the congenital malformations. This is the first report of a Gardner syndrome patient with an interstitial deletion of 5q.

A fluorordeoxyuridine (FdU) synchronization technique was applied to 30 chorionic villus samples (CVS) from patients undergoing first trimester fetal diagnosis. The villi were incubated for 15 h in the presence of FdU. The block in DNA synthesis was subsequently released using thymidine and after an additional 5 h of incubation the mitotic cells were arrested in metaphases using a high concentration of colcemid. This method results in improved morphology of the chromosomes and a high mitotic index. A diagnostic chromosome analysis could be obtained in each clinical case using at least 15 well-spread metaphases. G-banded karyotypes were prepared of four metaphases in each case. The diagnostic procedure was completed within 48 h from the time of CVS. Use of this technique significantly improves the success rate of 'direct' chromosome analyses from CVS in a busy cytogenetic laboratory.

Methods ASCERTAINMENTSixty-four patients with the diagnosis of RTS were ascertained through the Rubinstein-Taybi Parent Group (47 (73%)) and referrals from other genetic centres (17 (27%)). Clinical data, photographs, and medical records were collected on each patient to confirm the diagnosis of RTS. Thirty-nine specific traits, including growth parameters, were assessed for each patient. Since RTS is a short stature syndrome, microcephaly in this context was used as 1 SD below the 50th centile height age to assess true microcephaly in relation to body size and not small head size resulting from overall growth deficiency. Clinical assessment was made before knowledge of deletion status to minimise potential bias and to test the hypothesis that there are clinically distinguishable differences between deletion and non-deletion patients. CYTOGENETIC STUDIESPeripheral lymphocytes were cultured for 72 hours using conventional methods. Karyotyping with GTG banding was performed at the 550 to 750 band level. A minimum offive metaphase preparations were examined from each patient. MOLECULAR STUDIESThe RT1 cosmid (D16S237), approximately 56 kb in size, was obtained in an E coli MC 1046 host. The presence of the probe was confirmed by digestion with EcoRI, which yielded a specific 5.2 kb fragment. The cosmid was

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We present a patient with features suggestive of Seckel syndrome who was found to be mosaic for ring 4 chromosome. Seckel syndrome is a rare entity characterized by marked growth retardation, microcephaly, facies characterized by receding forehead and chin, large beaked nose, and severe retardation, usually thought to be inherited as an autosomal recessive condition. In addition, our patient had oligomeganephronia, a rare and usually sporadic renal malformation, previously reported in two other patients with abnormalities of chromosome 4. Besides pointing out the overlap between the Seckel phenotype and Wolf-Hirschhorn syndrome, our patient illustrates the need to consider cytogenetic studies in patients with the Seckel phenotype, so that accurate diagnoses can be given to families. Also, the case suggests that there may be a locus for oligomeganephronia distal to the Wolf-Hirschhorn critical region on 4p.