120 Case report A 33-year-old woman (1.85 m, 110 kg) presented to our out- patient clinic complaining about pain localized at the distal half of the left tibia, which did not respond to analgesics. Symptoms had begun eight years ago with mild pain and swelling in the area (with no history of trauma) that appeared occasionally thereafter. Two months before her visit, the pain became severe and constant leading to ambulatory discomfort. Inspection of the left limb revealed swelling of the tibia and wasting of the calf (Figure 1A). On palpation, there was a painful area matching the area the patient was complaining about. Knee movements were free and painless, while move- ments of the ankle joint were restricted and painful. Initial X-ray examination showed large expanded in- tramedullary lesions in the distal tibia shaft with homogeneous “ground glass” appearance, endosteal scalloping, but no pe- riosteal new bone formation (Figure 1B). Further evaluation with computed tomography (CT) demonstrated widening of the tibia shaft, thinned cortices and sharply defined homoge- neous high-density lesions of amorphous texture with uninter- rupted sclerotic margins at the medullary cavity (Figure 1C). Assessment of bone metabolism with biochemical markers was indicative of high bone turnover [serum bone alkaline phosphatase: 61.5 μg/L (reference range-r.r. <14.3 μg/L), serum osteocalcin: 116.2 ng/ml (r.r. 12-41 ng/ml), serum Cross Laps: 0.623 ng/ml (r.r. <0.54 ng/ml), serum PINP: 317.8 ng/ml (r.r. 16.3- 73.9 ng/ml)]. The patient underwent a Tc-99m bone scan which revealed homogeneous enhancement in the left tibia, the left femur, the 7 th right rib (anterior and posterior part) and the left ankle joint (Figure 1D). Further assessment with blood and urinary tests did not reveal other medical problems. Based on the clinical and imaging findings the predominant diagnosis was that of polyostotic fibrous dysplasia (FD). The patient denied a confirmatory bone biopsy, so genomic analy- sis offered an alternative approach, since FD has a demon- strated association with somatic mutations at codon 201 of the α subunit of G protein (Gsα), encoded by the GNAS gene. Ge- nomic DNA was extracted from peripheral blood and Sanger sequencing analysis was performed in triplicates using one pair of primers designed to cover the known mutations of the GNAS gene that had been linked to FD. The R201C mutation was detected using Chromas software (Chromas Lite 2.01) and BLAST in the patient (Figure 2). We opted to start treatment with intravenous bisphospho- nates (5 mg zoledronic acid every six months). After approx- imately five months since the first infusion, the patient reports a significant improvement in the level of pain. Commentary Fibrous dysplasia of bone is a benign, non-inheritable dis- ease characterized by bone pain, bone deformities and frac- tures. It was first described by Lichtenstein in 1938. Its prevalence is approximately 1 in 30,000 individuals; sex dis- tribution is equal and it is thought to account for 5 to 7% of benign bone tumors. FD affects either one bone (monoostotic form - around 60% of patients) or multiple bones (polyostotic form - around 40% of patients). Less than 5% of the patients also have endocrine abnormalities (most often precocious pu- J Musculoskelet Neuronal Interact 2013; 13(1):120-123 Fibrous dysplasia; confirmation of clinical diagnosis by DNA tests instead of biopsy I.P. Stathopoulos 1,2 , A.P. Balanika 3 , C.S. Baltas 4 , K. Lampropoulou-Adamidou 1,2 , T. Koromila 5 , P. Kollia 5 , S. Tournis 1 , N.A. Papaioannou 1 , A. Katsalira 1 1 Laboratory for the Research of the Musculoskeletal System “Theodoros Garofalidis”, University of Athens, KAT hospital, Athens, Greece; 2 Third Orthopaedic Department, University of Athens, KAT hospital, Athens, Greece; 3 Computed Tomography Department, General Hospital “Asklepieio Voulas”, Athens, Greece; 4 Radiology Imaging Department, General Hospital of Athens “G. Gennimatas”, Athens, Greece; 5 Laboratory of Human Genetics, Department of Genetics & Biotechnology, Faculty of Biology, University of Athens, Athens, Greece Keywords: Fibrous Dysplasia, GNAS Mutation Clinical Quiz Hylonome The authors have no conflict of interest. Corresponding author: Ioannis P. Stathopoulos, MD, MSc, Laboratory for the Research of Musculoskeletal System “Th. Garofalidis”, University of Athens, KAT Hospital, 10, Athinas str., Kifissia, 14561, Athens, Greece E-mail: ipstathopoulos@gmail.com Edited by: P. Makras Accepted 11 February 2013