Growth in height and body proportion from birth to adulthood in hereditary hypophosphatemic rickets: a retrospective cohort study

Abstract

Purpose: Patients with hereditary hypophosphatemic rickets are short and disproportionate and very little information is available on segmental growth, but the body disproportion at adulthood leads us to think that the growth velocity of legs is slower. Methods: A total of 96 children were included and molecular testing was carried out in 42. Children who reached adult height were classified into two groups according to their compliance to conventional treatment (phosphate supplement and calcitriol). Individual growth records of height and sitting height/height were plotted using Argentine reference data in 96 children and growth curves were estimated by fitting Preece-Baines Model 1 in 19 of the children. Results: Molecular testing revealed sequence deleterious alterations or large deletions in 36/42 patients. During childhood, 76% of children grew below − 1.88 standard deviation score (SDS) and 97% had body disproportion. During adolescence, the mean peak height velocity for the good and poor compliance to treatment groups was 7.8 (0.6) and 5.4 (0.4) cm/year in boys and 7.0 (0.7) and 5.2 (0.8) cm/year in girls, respectively. At adulthood, the median sitting height/height ratio was 2.32 and 6.21 SDS for the good and poor compliance to treatment groups, respectively. The mean pubertal growth spurt of the trunk was –0.8 (1.4) SDS, with a short pubertal growth spurt of − 1.8 (0.4) SDS for limbs in the good compliance group. Median adult height in 13/29 males and 30/67 females was –4.56 and –3.16 SDS, respectively. Conclusion: For all patients the growth spurt was slower, secondary to a short growth spurt of limbs, reaching a short adult height with body disproportion that was more prominent in the poor compliance group.