Growth in children with X-linked hypophosphataemic rickets.

Currently, X-linked hypophosphataemic rickets (XLHR) is most commonly treated with a combination of phosphate and vitamin D, but there is conflicting evidence about the effects of this treatment on linear growth. In all, 25 patients with XLHR (current age range, 4.1-22.1 years; median, 8.2 years) were studied to determine whether there was any improvement in height SDS during treatment. The duration of therapy was 2.9-15.0 years (median, 5.7 years). Measurements before the age of 2 years or after the onset of puberty were excluded to remove the effects of measurement difficulties in small infants and of variation in pubertal timing. The growth of these patients was compared with a similar group of untreated historical controls. Patients treated with calcitriol and phosphate for at least 2 years before the onset of puberty (n = 22) had a significantly better mean height SDS than the historical controls (-1.23 compared with -2.05 for the historical controls; p = 0.02). Among patients treated with calcitriol and phosphate for at least 2 years (n = 21), the change in height SDS had a positive correlation with the duration of therapy (r = 0.51; p = 0.02). The growth of children with XLHR treated with combination therapy was thus significantly better than that of historical controls.