Dermatoglyphic peculiarities in families with X‐linked mental retardation and fragile site Xq27: a collaborative study

The dermatoglyphic patterns of fingertips, palms and soles of 75 male patients with X‐linked mental retardation and fra‐Xq27 and of 28 obligate female heterozygotes were analyzed and compared with the data from 200 S and 200 control individuals. The results show that there is a strong association between the fra‐X‐syndrome and dermatoglyphic peculiarities observed in male patients and also in female heterozygotes. The characteristic dermatoglyphic features of the fra‐X‐syndrome are: increased frequencies of radial loops, whorls and arches on the fingertips, a pronounced transversal course of palmar ridges, lower a‐b RC, absence of c‐triradii on the palms, abnormal palmar and plantar creases, dysplasia of the papillary ridges and low frequencies of true patterns on the soles. Some of these patterns were found in the female carriers of fra‐Xq27 also. The combination of palmar and plantar patterns, expressed by a “log. score‐Index”, provides a high degree of discrimination between the male patients with fra‐X‐syndrome and the control group. A preliminary log. score‐Index was developed also for the female heterozygotes.