Age-related stature and linear body segments in children with X-linked hypophosphatemic rickets

Abstract

Children with X-linked hypophosphatemic rickets (XLH) are prone to severe stunting. A multicenter mixed-longitudinal study was conducted to assess age-related stature, sitting height, arm and leg length in XLH patients on continuous treatment with phosphate and calcitriol. Mean standard deviation scores (SDS) for all body dimensions were markedly reduced and differed significantly among each other at the initial and subsequent evaluations (baseline: stature -2.48 SDS; sitting height -0.99 SDS; arm length -1.81 SDS; leg length -2.90 SDS; each p<0.001). A strong association between stature and leg length (r (2)=0.87, p<0.001) was noted. Leg length SDS decreased progressively during childhood (2-9 years) and adolescence (12-15 years; each p<0.001). Sitting height SDS increased significantly during late childhood, indicating uncoupled growth of the legs and trunk and resulting in an ever increasing sitting height index (i.e. ratio of sitting height to stature; age 2 years 2.0 SDS; age 10 years 3.3 SDS; p<0.001) that was associated with the degree of stunting (r (2)=0.314, p<0.001). Mean serum phosphate levels were positively associated with stature and leg length, but negatively with sitting height index. Based on these results, we can conclude that growth of the legs and trunk is uncoupled in XLH and related to serum phosphate levels.

Three-Year Growth Hormone Treatment in Short Children with X-Linked Hypophosphatemic Rickets: Effects on Linear Growth and Body Disproportion

“…This was mainly due to a continuously diminished leg growth during the prepubertal growth period and was significantly associated with the degree of hypophosphatemia, whereas the degree of leg bowing appeared to be only a weak correlate. By contrast trunk growth was less severely affected in XLH (18). Together this discordant growth pattern results in a markedly elevated sitting height index (i.e.…”

“…Stature and size of three longitudinal body segments (i.e. sitting height and arm and leg length) were measured yearly, and data for stature and sitting height were used to calculate the sitting height index (18). A detailed description of the underlying procedures and the definition of these compartments have been published previously (32,33).…”

“…Furthermore, this treatment does not allow normal growth in the majority of patients (13)(14)(15)(16)(17). Indeed, a recent study on longitudinal growth in a large cohort of XLH patients on regular treatment with phosphate and calcitriol disclosed progressive disproportional stunting (18). This was mainly due to a continuously diminished leg growth during the prepubertal growth period and was significantly associated with the degree of hypophosphatemia, whereas the degree of leg bowing appeared to be only a weak correlate.…”

“…Together this discordant growth pattern results in a markedly elevated sitting height index (i.e. ratio between sitting height and stature), and as a rule of thumb, the shortest patients present with the highest degree of body disproportion (18).…”

Patterns of Growth after Kidney Transplantation among Children with ESRD

“…The sitting height index was calculated as the ratio between sitting height and stature as a measure of body disproportion (17). All measurements were performed as recommended by the International Biologic Program (18) with standardized equipment (height: Dr. Keller, I Stadiometer-Limbach-Oberfrohna, Germany; all other measurements: Siber Hegner Anthropometer, Zürich, Switzerland; accuracy, 1 mm).…”