A COMPARISON OF THE DYSPLASTIC MIDDLE PHALANX OF THE FIFTH FINGER IN MENTALLY NORMAL CAUCASIANS, MONGOLOIDS, AND NEGROES WITH THAT OF INDIVIDUALS OF THE SAME RACIAL GROUPS WHO HAVE DOWN’S SYNDROME

¹ Professor of Anatomy, Emeritus, Stanford University School of Medicine, Stanford, California.

Dysplasia of the middle phalanges of the fifth fingers occurs with considerable frequency among some mentally normal Mongoloid peoples, e.g., Japanese, Chinese, American Indians, and also among Caucasians and persons of other races who have Down’s syndrome (mongolism).

The type of dysplasia is, however, different in the 2 groups. In Down’s syndrome, the abnormal phalanx is typically shortened, disproportionately wide, and, frequently, wedge-shaped, and it is usually associated with clinodactyly. In mentally normal Mongoloid peoples, the dysplastic phalanx is characterized by a concave de fect in the base of its diaphysis and by a cone-shaped or mushroom-shaped epiphysis. Clinodactyly is not a constant feature of this type of phalangeal dysplasia. Moreover, in mentally normal Mongoloid groups, the defect occurs more than twice as frequently among the females aS among the males. In Down’s syndrome, however, slightly more males than females are affected.

Dysplastic middle phalanges of the fifth fingers are another example of morphologic features which occur among both mongoloid defectives and mentally normal Mongoloid peoples. Like most of the other features of mongolism that resemble physical characters of normal Mongoloid peoples, a careful comparison discloses that the resemblances between them are only superficial and that they are quite different in the 2 groups.

Since both of these types of dysplasia result in an abnormal shortening of the phalanx involved, the term "brachymesophalangy" alone is not a satisfactory designation, because it fails to distinguish between them. An adequate description requires that one specify, also, the type of dysplasia associated with the phalangeal shortening in the individual or groups that one is describing.

CiteULike    Complore    Connotea    Del.icio.us    Digg    Reddit    Technorati    What's this?