Ring Chromosome and Clinical Findings: Reports Cases of 4 Different Chromosomes in Beninese Population

Ring chromosome is a disorder in which one or both ends of chromosome are lost and joined, so they could show a ringshaped structure. Patients with ring chromosome could therefore present with features of deletionof long or short arms of the chromosome syndromes or a combination of both. Phenotypic of these individuals depends on the size of the ring chromosome, amount of genetic material lost in breakage, the stability of the ring chromosome and the presence of secondary chromosomal aberrations including the varying degrees of mosaicism. Ring chromosomes accounts for a very low percentage of structural chromosomal abnormalities but could lead to a major clinical concern and complicated genetic counseling. Practitioner awareness must be permanently raised up to help in managing with efficacy patient with ring condition. We report here 4 cases of ring on chromosome 4, 9, 15 and X. We described their clinical finding and draw attention on common key signs that were present in the reported cases and also discussed recurrence risk. A ring chromosome is a chromosome whose arms have fused together to form a ring. Ring chromosomes were first discovered by Lilian Vaughan Morgan in 1926. Constitutional ring chromosomes have been identified for each of the human chromosomes and the overall frequency is estimated at 1 in 27:000 to 62:000 births [2]. Rings result from rare intrachromosomal fusions although mechanisms underlying chromosomal ring formation are not completely understood. These fusion events are hypothesized to arise from either unstable telomeres, which directly fuse, or from chromosomal breaks that resolve by fusion of the two chromosomal arms. Phenotype of these individuals depends on the size of the ring chromosome, amount of genetic material that is lost in breakage, the stability of the ring chromosome and the presence of other type of chromosomal abnormalities including mosaicism.