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Introduction
Hypophosphatemic osteomalacia (HO) is an uncommon metabolic disease characterized by low concentrations of serum phosphate levels, which leads to reduced mineralization of the bone matrix (1). It may affect individuals of all ages and either gender. Typically, HO is either inherited (2), a result of tumor-induced osteomalacia (TIO) (3), drug-induced (4) or a symptom of chronic kidney disease (5). Patients with inherited or TIO have been widely reported on by endocrinology or oncology specialists, however HO is often misdiagnosed in clinical practice as ankylosing spondylitis (AS), chronic arthritis, lumbar disc disease, osteoporosis and somatoform disorder, as it typically presents with the same signs and symptoms of these rheumatologic diseases, including bone pains, thoracic or back pain, muscle weakness, proximal myopathy and arthralgia (6). Diagnosis of HO remains a challenge to rheumatologists and physicians due to its low prevalence and nonspecific manifestations. Screening blood tests for electrolytes, particularly serum phosphate and bone mineral density (BMD) is basic clue for diagnosis. Screening for hidden tumors, which are classified as phosphaturic mesenchymal or phosphaturic mesenchymal tumor mixed connective tissue variants is important for patients with HO without an obvious etiology or history. The majority of the tumors are of bone or soft tissue origin and positron emission tomography (PET)/computed tomography (CT) scans may be used to identify them (3). The prognosis of the disease depends on the etiology. The treatment or removal of secondary etiologies, including drugs and tumors has been reported to be particularly effective at improving the condition. It is necessary to supply basic supplementation to all patients with sufficient oral phosphate, elemental calcium and active vitamin D (7). The present study reported 9 misdiagnosed cases of HO in order to improve the recognition of this disease amongst rheumatologists and physicians. Adefovir dipivoxil-induced Fanconi syndrome was present in 6 of the cases, 2 were caused by tumors and 1 case was due to chronic nephropathy.
Case report
Patients
A total of 9 patients with terminal diagnoses of HO were diagnosed and treated in the Department of Rheumatology at Guangdong General Hospital (Guangzhou, China) between January 2011 to August 2015. All patients had clear etiologies and no family history of the disease. The length of disease history ranged from 10 months to 5 years, and the...