Hip fracture leading to the diagnosis of autosomal dominant hypophosphatemic rickets. A case report.

A 38 year-old Caucasian female (weight: 67 Kg, height: 163 cm) was referred to our department after surgical treatment of a non-healing hip fracture, due to severe hypophosphatemia. During the previous ten months she suffered from worsening generalized bone pain, especially at the left hip, and proximal muscle weakness. There was no history of trauma. Past history revealed two distinct episodes of diffuse musculoskeletal pain following her pregnacies at 28 and 34 years respectively, that resolved spontaneously after three months. Family history was negative, and her two children (ten and six-years old males, respectively) had normal phosphate levels (4.6 mg/dl and 4.3 mg/dl, childrens normal range: 3.6-5.8 mg/dl). On clinical examination there were no lower extremity deformities. Radiology investigation (Figure 1A) revealed a transcervical fracture of the left femur with delayed union and varus deformity, looser zones on pubic rami and right ischial ramus and diffuse osteopenia with biconcave deformation of lumbar vertebrae. Bone mineral density at the right hip was quite below the expected range for age (FN: 0.556 mg/cm, Z-score: -3.8). Laboratory investigation revealed severe hypophosphatemia (1.7 mg/dl), phosphaturia (TMP/GFR: 1.4 mg/dl), normal calcium, iPTH and 25(OH) D levels, elevated total and bone specific alkaline phosphatase, while calcitriol levels were inappropriately normal (Table 1). Urinary amino-acid excretion was norJ Musculoskelet Neuronal Interact 2013; 13(3):391-394