Ring (13),t(2;6) associated with familial fragile (16).

Fragile sites consist of isochromatid chromosome breaks which take place at specific sites along a chromosome and segregate as simple Mendelian traits.1 2 While the Xq28 fragile site is regarded as a marker for X linked mental retardation, the fragile sites on autosomes are regarded as normal uncommon variants. The present case supports the idea that the presence of fragile sites may constitute a risk factor which should be taken into account in clinical diagnosis. In addition, a fragile site may indicate some chromosomal instability. The patient described here is the third child of a young non-consanguineous couple with no known exposure to mutagenic or teratogenic agents. The other two children