Communications Mongolism ( down ' S Syndrome ) and Keratoconus

MONGOLISM was first described as a clinical entity and differentiated from cretinism by Langdon Down (1866). During the past few years there has been a revival of interest in the condition because of the discovery that the cells of patients with this anomaly contain an abnormal number of chromosomes. At the same time, keratoconus has been described by some European authors as one of the commoner ocular manifestations of the disease, and it has also been suggested that acute keratoconus is a not unusual complication in these patients. Until 1956 it had always been believed that human cells contained 24 pairs of chromosomes derived equally from each parent. In that year, however, Tjio and Levan (1956) showed that our cells have only 46 chromosomes or 23 pairs, comprising one pair of sex chromosomes (the X and Y chromosomes) and 22 pairs of somatic chromosomes or autosomes. Their discovery was quickly confirmed by other workers and is now universally accepted. In man abnormal chromosome numbers arise by non-separation of one of a pair of chromosomes in the first meiotic division. Such an occurrence involving the sex chromosomes was reported by Jacobs and Strong (1959), and has now been shown to give rise to different clinical syndromes such as gonadal dysgenesis or Turner's syndrome, where the total chromosome number is 45 (XO), and also to Klinefelter's syndrome (XXY) and the Triple X or superfemale syndrome (XXX), in both of which 47 chromosomes have been found. In these conditions the main abnormalities lie in the reproductive systems, although some of these patients are also mentally retarded. It is also possible that non-separation of any one of the 22 pairs of autosomes could occur in man, and thus trisomy or tripling of these chromosomes of 22 varieties is within the bounds of possibility. The first autosomal trisomic syndrome described was that of mongolism by Lejeune, Gauthier,