Dermatoglyphic and cytogenetic studies in parents of children with trisomy 21.

Dermatoglyphic studies were carried out of 131 mothers and 95 fathers of children with Down syndrome and 200 controls (100 males and 100 females) using the Hopkins single score method. Twelve percent of the mothers and 2% of the fathers showed dermatoglyphic abnormalities including a distal axial triradius (t"), hypothenar ulnar loops, radial loops on digits IV and V and abnormal palmar creases, resulting in a positive Hopkins score or a score in the "overlapping range" (greater than -3). The origin of the extra chromosome could be determined in 23 of a total group of 40 families. In 22 of the former, the mother was the donor of the extra chromosome; in one it was the father, In these 23 families, a Hopkins score in the overlapping range was found in three mothers who were all under the age of 35 years at the birth of the affected child. Since cytogenetic studies cannot easily differentiate between meiotic nondisjunction and mosaicism as a basis for 21 trisomy in the progeny, it is possible that mothers with positive overlapping Hopkins scores represent undetected mosaics for a trisomic cell line. The dual approach utilizing dermatoglyphic and cytogenetic studies may aid in identifying persons with an enhanced risk for having children with Down syndrome.