Ring Chromosome 7

In general, ring chromosomes (RCs) are among the rarest constitutional chromosomal aberrations. Hereby, chromosome 7 comprises only 23 postnatal and one prenatal clinical case with RC formation. Reasons are not clear yet, even though it is noteworthy, that chromosome 7 is underlying imprinting, which may have a negative effect on viability of RC7 carriers. It is interesting that all yet reported 24 cases of RC7 have three typical clinical features growth retardation, pigmented skin nevi, and microcephaly commonly seen in 92%, 83%, and 67% of patients, respectively. Besides, due to the small number of available cases, it is hardly possible to distinguish effects of RC-induced genomic imbalances and the effects of the practically always present mosaic cell line with a monosomy 7. RC7 can be found as acquired chromosomal changes in tumors occasionally, enhanced risk for malignant melanoma has been reported in constitutional cases, as a result of the mentioned pigmented skin nevi.