A New Radiographic Finding in Mongolism

Abstract

The radiographic manifestations of Down's syndrome have been described by many authors. Recently, several new stigmata have been published (3–5). The pelvic characteristics in this syndrome, as described by Caffey and Ross (1, 2), remain the most constant radiologic abnormalities; but in a small percentage of infants the pelvis is normal. The roentgen diagnosis of mongolism, therefore, must be substantiated by other findings, and finally by chromosomal analysis. The purpose of this paper is to present a new radiologic finding and to show its relatively high incidence in this chromosomal abnormality. Figure 1 is the chest radiograph of a newborn girl first seen because of duodenal atresia. Although the infant was clinically mongoloid, the pelvic radiograph disclosed normal iliac and acetabular contours. However, accessory sternal ossification centers (4) and congenital heart disease were present. In addition, only 11 pairs of ribs were counted. Genetic studies revealed a trisomy of the No. 21 chromosome. Because of the finding of 11 pairs of ribs, the authors subsequently reviewed the radiographs of 50 children afflicted with Down's syndrome. Of the 29 females studied, 11 pairs of ribs were found in 38 per cent of the cases (11 of 29). Of 21 males examined, the incidence of 11 pairs of ribs was found to be 14 per cent (3 of 21). Pionnier and Depraz reviewed 10,000 chest examinations and reported the presence of 11 pairs of ribs in only 3 cases. By comparison, the authors reviewed 200 consecutive chest radiographs in children and discovered that 6 per cent of the females and 2 per cent of the males demonstrated 11 pairs of ribs. In all the cases reviewed by the authors, in which 11 pairs of ribs were present, the absence of one dorsal vertebra was postulated. A finding of interest in this instance was a hemivertebra and its rib at the T3-4 level, apparently a forme fruste of the 11-rib form (Fig. 2). Summary and Conclusions A heretofore unreported radiographic finding in Down's syndrome is described. The presence of 11 pairs of ribs in a relatively high percentage of mongoloid children affords the radiologist an additional feature in this syndrome. Other chromosomal abnormalities must be surveyed to determine if this finding can be considered as an exclusive feature of Down's syndrome or as a feature of trisomy.