An extra small metacentric chromosome in association with multiple congenital abnormalities.

Excess genetic material in the form of a small metacentric chromosome, often smaller than a member of the G group, has been reported in a number of cases (Ilberry, Lee, and Winn, 1961; Fr0land, Holst, and Terslev, 1963; Uchida et al, 1964; Taft, Dodge, and Atkins, 1965; Gustavson, Atkins, and Patricks, 1964, Crawfurd and Lele, 1965; Tamburro and Johnson, 1966; Gamstorp, Hfikansson, and Lagergren, 1966; Ferrante et al, 1968). In some patients with this small extra chromosome there have been suggestions of which chromosome part was in triplicate, as in the cases described by Stevenson, Patterson, and Goodman (1966), with an isochromosome of the short arms of D, with a C/D translocation (Insley, Rushton, and Jones, 1968), with a G/G translocation (Mukerjee and Burdette, 1966) and with incomplete D trisomy (Ishmael and Laurence, 1965). Also a phenotypically normal mother and her son with oligospermia were found to have an extra small metacentric chromosome (Smith et al, 1965). In the majority of the cases reported, it has not been concluded which chromosome or chromosome part is in triplicate, but some of the patients with the abnormal chromosome have had features suggestive of Down's syndrome (Ilberry et al, 1961; Dent, Edwards, and Delhanty, 1963; Gustavson et al, 1964; Dekaban and Zelson, 1968). A child with mental retardation and multiple congenital abnormalities in association with an extra metacentric chromosome which is smaller than a member of the G group is reported here. No conclusion is reached about the origin of the extra chromosome material.