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Treatment of Hypophosphatemic Rickets in Children

Aleksandra Kaplina
Department of Pediatrics, Saint-Petersburg State Pediatric Medical University

Background: Hypophosphatemic rickets (HR) is a hereditary disease, characterized by hypophosphatemia, phosphaturia, reduced tubular reabsorbtion of phosphate (TRP%), low maximal tubular phosphate reabsorbtion per glomerular filtration (TmP/GFR). HR includes autosomal dominant (ADHR), recessive (ARHR), X-linked HR, hypophosphatemic bone disease (HBD), hereditary HR with hypercalciuria (HHRH). Patients with HR need a lifelong phosphate replacement therapy.

Objective: to analyze the effect of phosphate replacement and active vitamin D therapy in children with HR.

Methods: Twenty eight children (for aged 2 to 16 years; 18 girls, 10 boys) with HR were included in the study. They have been receiving phosphate, active vitamin D therapy for 7 years (median duration). Children were followed 6 monthly. The outcome measures: height changes; TRP%, TmP/GFR (Schwartz), fractional excretion of phosphate (FEP%), urinary P/Cr, Ca/Cr; serum phosphate and alkaline phosphatase (ALP) levels.

Results: The patients were matched by HR type (genealogical method): ADHR, X-linked HR – 13 children, HBD – 5, ARHR – 6, HHRH – 4. HR children had impaired height at the baseline, which increased to age norm in 9 (32.1%) patients (mostly ADHR). ADHR, X-linked HR children had an increase of TRP to 75.1±10.3% (baseline 70.3±15.8%; M±SD). ALP decreased to 835.4±442.5 (from 1055.9±347.4) at the outcome. Patients with HBD had slightly changed serum phosphate levels, P/Cr at baseline; TRP normalized. ARHR children had the highest ALP (1173.5±243.4), low TRP (70.3±12.5%) in outcome. HHRH patients weren’t administered active vitamin D. They had TmP/GFR increased (0.47±0.2), FEP significantly decreased (19.5±8.5; p=0.044) from baseline. HR patients had increased FEP in outcome. Seven children had metaphyseal-deaphyseal osteotomy to correct leg deformities: ADHR, X-linked HR – 3, ARHR – 3, HHRH – 1.

Conclusion: Phosphate replacement therapy had a positive effect on height, ALP, TRP in children with HR. The biggest effect had been in patients with ADHR, X-linked HR. HBD had a favorable course, patients didn’t need surgical treatment.

Aleksandra Kaplina
Aleksandra Kaplina
Almazov National Medical Research Centre








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