History and Geography

Probably the earliest record of Down syndrome was a Saxon skull excavated in the seventh century showing osteological changes consistent with the condition. There are also accounts of sixteenth-century paintings of children having the features of the syndrome. The first accounts of Down syndrome, however, did not appear until the nineteenth century. In 1846 E. Sequin wrote of a specific type of mental retardation case, which he described as a "furfura-ceous cretin with its white, rosy, and peeling skin, with its shortcomings of all the integuments, which give an unfinished aspect to the truncated fingers and nose; with its cracked lips and tongue; with its red ectropic conjunctiva, coming to supply the curtailed skin at the margin of the lids" (quoted in Brousseau and Brainerd 1928). The first formal description was given in a report by J. Langdon Down in 1866. He described a type of congenital defect bearing resemblance to the Tartar race which he called Kalmuc or Mongolian. Down, who had been influenced by the racial hypothesis and the writings of Charles Darwin, suggested that the entity represented a reversion to an earlier phylogenetic type. This hypothesis never gained wide acceptance, and in fact, Down's own son, also a doctor, disagreed with it, suggesting that the features of the syndrome were accidental and superficial (Brain 1967).

The next important reports were presented by John Fraser and Arthur Mitchell in 1875 at the Royal College of Physicians in Edinburgh. Mitchell pointed out the similarities between the syndrome and "cretinism" (congenital hypothyroidism). Reports by W. W. Ireland and G. E. Shuttleworth followed during the 1870s and 1880s. Shuttleworth suggested that children with the condition were actually "unfinished," representing the persistence of anatomy characteristic of a particular phase in fetal development. He specifically cited the already recognized association between the syndrome and advanced maternal age, pointing out the large number of children with Down syndrome who were the last-born in large families. During the end of the nineteenth and beginning of the twentieth centuries, many reports appeared, expanding the description of the syndrome's phenotypic manifestations. Important among these were the extensive neuropathologi-cal descriptions by A. W. Wilmarth presented in reports from 1885 to 1890.

From the initial description in the mid-nineteenth century to 1959, a large number of etiologic hypotheses were advanced for the syndrome, including maternal syphilis, familial tuberculosis, familial incidence of epilepsy, insanity, instability, and mental retardation. Once the increased incidence of congenital heart disease in the syndrome was recognized by John Thomson and A. E. Garrod in 1898, a cause in early fetal existence was sought. Among theories advanced were maternal alcoholism, fetal hyperthyroidism, maternal dysthyroidism, hypoplasia of the adrenals, dysfunction of the pituitary, abnormality of the thymus, chemical contraceptives, curettage, faulty implantation, degeneration of the ovum, and emotional shock in early pregnancy.

As early as 1932, a chromosomal anomaly was suggested as a possible cause of the disorder (Bleyer 1934). In 1959, shortly after the correct diploid number of chromosomes in the human cell was established, a small sample of children with Down syndrome were demonstrated to have an extra acrocentric chromosome and a total chromosome number of 47 in cultures of fibroblasts. This finding was verified by subsequent studies. Later in the same year, J. A. Book and co-workers (Book, Fraccaro, and Lindsten 1959) concluded that the extra chromosome was most similar to number 21 in the Denver classification. In 1960, other investigators reported the case of a girl with Down syndrome having only 46 chromosomes, and postulated a reciprocal translocation occurring between two chromosome groups (Polani et al. 1960).

Initially, Down syndrome was thought to occur only in the Caucasian race. Subsequently, however, reports have shown that it occurs in every racial group and country although thorough, well-designed studies have not allowed an accurate picture of its true distribution across racial and ethnic groups. Early reports indicated a low incidence in African and black American groups. However, recent investigations in Ibadan, Nigeria, and in Memphis, Tennessee, found black incidence rates much the same as those of white populations (Janerich and Bracken 1986). Similarly, although detection in Oriental populations is thought to be' inhibited by sameness of features, recent studies in Japan reveal rates much like those in the United States. An extensive study from the World Health Organization in 1966 indicated that a low incidence of Down syndrome is reported in India, Malaysia, and Egypt (Lilienfeld 1969), whereas by contrast a high incidence was reported in Yugoslavia, Czechoslovakia, and at least one location in Melbourne, Australia.

A. M. Lilienfeld (1969) summarized 11 studies that attempted to indicate the spatial and temporal clustering of the syndrome. However, even the most sophisticated of these, carried out in Melbourne, Australia (Collman and Stoller 1962), failed to give satisfactory statistical proof for clustering. A 1983 report by P. M. Sheehan and I. B. Hillary describes a cluster of children with Down syndrome born to women who attended the same boarding school in their youth. This suggests that in some instances, an environmental agent may influence the incidence of Down syndrome.

Christine E. Cronk

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