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AB0835 Acquired Hypophosphatemic Osteomalacia: A Very Easy to Misdiagnosed or Neglected Disease for Rheumatologists – 6 Cases Report and Review of Literature
  1. L. Li
  1. Department of Rheumatology, Guangdong General Hospital, Guangdong Academy of Medical Sciences, Guangzhou, China

Abstract

Background Hypophosphatemic osteomalacia (HO) is a metabolic disease caused by hypophosphatemia and characterized with disturbance of bone mineralization. The most common reasons are genetic and tumor (tumor induced osteomalacia, TIO). Secondary to drug-induced and sporadic are rare. It is apt to be misdiagnosed with ankylosing spondylitis (AS), chronic arthritis or osteoporosis because of the mimic signs and symptoms of rheumatologic diseases. In fact it is challenging not only for rheumatologist but also other physicians.

Objectives To remind rheumatologists to recognize hypophosphatemic osteomalacia (HO) from mimic rheumatology disease.

Methods Retrospectively analysis clinical data of 6 cases with acquired hypophosphate osteomalacia (HO) who were misdiagnosis with mimic rheumatology diseases at beginning, and then do a literature review.

Results 5 males and 1 female, age from 22 to 47 years old (means 38 ys). Etiology of 3 were adefovir dipivoxil induced Fanconi syndrome, 2 were tumor, 1 was chronic nephropathy complicated with tubular acidosis. Chief complaint of all cases was thoracic and/or back pain and arthralgia, followed by progressive muscle weakness and dramatic movement limitation. All patients had transferred 3 to 6 hospitals and departments for the longest 5 years with misdiagnosis, such as ankylosing spondylitis, chronic arthritis, lumber vertebral disc disease, osteoporosis and even somatoform disorder. The corresponding treatments had no effects for pain relieve and symptoms improvement. Hypophosphatemia is typical in all cases. Bone scan of all cases showed diffusely decreased tracer uptake, with multiple hot spots of fractured sites and involved joints, significant low bone density compared to the same age and gender group. All cases accepted supplement of calcium, vitamin D and phosphate as basic therapy. 3 patients got recovery after adefovir dipivoxil stopped. Hypophosphatemia disappeared soon after resection of tumor in 1 case. One with sub-skull tumor and one with chronic kidney disease had poorly prognosis because of the uncured disease.

Conclusions The diagnosis of HO is challenging for rheumatologist and even physicians. Basic electrolyte examination and bone mineral density should be performed to unexplained young patients with thoracic and/or back pain and muscle weakness. Screening tumor in soft tissue and bone, carefully collect medical history in detail especially anti-hepatitis B viral drug- adefovir dipivoxil are key steps of early diagnosis for suspected patients. Remove the etiology can dramatically increase serum phosphate concentration, improve the clinical signs and symptoms with much better prognosis.

References

  1. Li Ling, Dong Guang-fu, Zhang Xiao, XIE Yue-sheng Adefovir dipivoxil-induced Fanconi syndrome and hypophosphatemic osteomalacia associated with muscular weakness in a patient with chronic hepatitis B.J South Med Univ.2011;31(11):1956-1957.

Acknowledgements The authors thank Marwin Gutierrez, MD for his expert assistance.

Disclosure of Interest None declared

DOI 10.1136/annrheumdis-2014-eular.2904

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