Association between X-linked hypophosphatemic rickets and Klinefelter's syndrome: effects on growth and body proportion.

Growth failure with disproportionate short stature is the major clinical feature of patients with X-linked hypophosphatemic rickets (HYP). We studied the pattern of linear growth and body proportion in an untreated normally growing HYP child also affected by Klinefelter's syndrome. Auxologic data were compared with those of a HYP half-brother who showed growth failure despite long-term treatment either with vitamin D or with vitamin-D-analog plus phosphate salt supplementation. The degree of body disproportion changed from negative values to positive values in the proband, whereas it was reduced in the half-brother. We conclude that, in the proband, the normal pattern of growth and the lack of the typical body disproportion as seen in HYP patients are attributable to the concomitant presence of Klinefelter's syndrome.