Hypophosphatemic rickets: A case of recurrent pathological fractures

Abstract

Introduction: Renal phosphate-wasting disorders are the most common form of hereditary rickets and osteomalacia in western countries, but are rarely reported in India. Therefore, we report here a case of hypophosphatemic rickets. Aim and objective: To report a case of hypophosphatemic rickets presenting with recurrent pathological fractures. Material and Methods: A 34-year-old premenopausal lady presented with recurrent pathological fractures, bone pain, and muscle weakness since 14 years of age. A thorough history was taken followed by clinical examination, and relevant biochemical and radiological investigations were done. Results: Height was 125 cm, arm span 145 cm, body weight 30 kg, and body mass index (BMI) 19.2 kg/m΂. Dental caries, kyphoscoliosis, shortening of left lower limb, bilateral coxa vara deformity of knee, muscle weakness, and bone tenderness were present. Calcium was 9.4 mg/dL, phosphorus: 1.8 mg/dL, albumin: 4.0 gm/dL, alkaline phosphatase: 360 U/L, creatinine: 0.4 mg/dL, a normal ammonium chloride (NH 4 Cl) loading test,24-hour urine calcium excretion: 102 mg/day, 25-hydroxyvitamin D3 [25(OH)D3]: 21.6 ng/mL, intact parathyroid hormone (PTH): 43.74 pg/mL, fraction excretion of phosphate (PO4): 40%, tubular maximum reabsorption of phosphate per unit of glomerular filtrate (TmP/GFR): 0.65 mg/dL, and fibroblast growth factor (FGF)23: 321.4 RU/mL. Skeletal X-rays showed multiple old fractures and pseudofractures. Magnetic resonance imaging (MRI) of the whole body showed no evidence of tumor. Fludeoxyglucose ( 18 F)-positron emission tomography (FDG-PET) computed tomography (CT) scan revealed metabolically active marrow with multiple areas of fracture and FDG-avid lesions in both lungs but no CT-based findings. Conclusion: Hypophosphatemic rickets or osteomalacia, possibly hereditary, is a rare cause of recurrent pathological fractures.

Keywords

• Hypophosphatemic rickets
• osteomalacia
• pathological fracture