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Open access

Shintaro Kawai, Hiroyuki Ariyasu, Yasushi Furukawa, Reika Yamamoto, Shinsuke Uraki, Ken Takeshima, Kenji Warigaya, Yuji Nakamoto and Takashi Akamizu

Summary

Tumor-induced osteomalacia (TIO) is a rare paraneoplastic syndrome characterized by renal phosphate wasting leading to hypophosphatemia due to excessive actions of fibroblast growth factor 23 (FGF23) produced by the tumors. Although the best way of curing TIO is complete resection, it is usually difficult to detect the culprit tumors by general radiological modalities owing to the size and location of the tumors. We report a case of TIO in which the identification of the tumor by conventional imaging studies was difficult. Nonetheless, a diagnosis was made possible by effective use of multiple modalities. We initially suspected that the tumor existed in the right dorsal aspect of the scapula by 68Ga-DOTATOC positron emission tomography/computed tomography (68Ga-DOTATOC-PET/CT) and supported the result by systemic venous sampling (SVS). The tumor could also be visualized by 3T-magnetic resonance imaging (MRI), although it was not detected by 1.5T-MRI, and eventually be resected completely. In cases of TIO, a stepwise approach of 68Ga-DOTATOC-PET/CT, SVS and 3T-MRI can be effective for confirmation of diagnosis.

Learning points:

  • TIO shows impaired bone metabolism due to excessive actions of FGF23 produced by the tumor. The causative tumors are seldom detected by physical examinations and conventional radiological modalities.

  • In TIO cases, in which the localization of the culprit tumors is difficult, 68Ga-DOTATOC-PET/CT should be performed as a screening of localization and thereafter SVS should be conducted to support the result of the somatostatin receptor (SSTR) imaging leading to increased diagnosability.

  • When the culprit tumors cannot be visualized by conventional imaging studies, using high-field MRI at 3T and comparing it to the opposite side are useful after the tumor site was determined.

Open access

Christopher Muir, Anthony Dodds and Katherine Samaras

Summary

Diamond–Blackfan anaemia (DBA) is a rare cause of bone marrow failure. The incidence of malignancy and endocrine complications are increased in DBA, relative to other inherited bone marrow failure syndromes. We describe an adult woman with DBA who developed osteoporosis and avascular necrosis (AVN) of both distal femora. Such endocrine complications are not uncommon in DBA, but under-appreciated, especially in adulthood. Further, rectal adenocarcinoma was diagnosed at age 32 years, requiring hemi-colectomy and adjuvant chemotherapy. Elevated cancer risk may warrant disease-specific screening guidelines. Genetic predictors of extra-haematopoetic complications in DBA are yet to be established.

Learning points:

  • Endocrine complications are common in DBA.

  • Clinical vigilance is required in managing bone health of DBA patients treated with glucocorticoids.

  • There is currently no reliable way to predict which patients will develop complications of therapy or premature malignancy related to DBA.

  • Complaints of bone or joint pain should prompt screening with targeted magnetic resonance imaging. Osteoporosis screening should be performed routinely.

Open access

Nobuhiro Miyamura, Shuhei Nishida, Mina Itasaka, Hirofumi Matsuda, Takeshi Ohtou, Yasuhiro Yamaguchi, Daisuke Inaba, Sadahiro Tamiya and Tetsuo Nakano

Summary

Hepatitis C-associated osteosclerosis (HCAO), a very rare disorder in which an extremely rapid bone turnover occurs and results in osteosclerosis, was acknowledged in 1990s as a new clinical entity with the unique bone disorder and definite link to chronic type C hepatitis, although the pathogenesis still remains unknown. Affected patients suffer from excruciating deep bone pains. We report the 19th case of HCAO with diagnosis confirmed by bone biopsy, and treated initially with a bisphosphonate, next with corticosteroids and finally with direct acting antivirals (DAA: sofosbuvir and ribavirin) for HCV infection. Risedronate, 17.5 mg/day for 38 days, did not improve the patient’s symptoms or extremely elevated levels of bone markers, which indicated hyper-bone-formation and coexisting hyper-bone-resorption in the patient. Next, intravenous methylprednisolone pulse therapy followed by high-dose oral administration of prednisolone evidently improved them. DAA therapy initiated after steroid therapy successfully achieved sustained virological response, but no additional therapeutic effect on them was observed. Our results strongly suggested that the underlying immunological alteration is the crucial key to clarify the pathogenesis of HCAO. Bone mineral density of lumbar vertebrae of the patient was increased by 14% in four-month period of observation. Clarification of the mechanisms that develop osteosclerosis in HCAO might lead to a new therapeutic perspective for osteoporosis.

Learning points:

  • HCAO is an extremely rare bone disorder, which occurs exclusively in patients affected with HCV, of which only 18 cases have been reported since 1992 and pathogenesis still remains unclear.

  • Pathophysiology of HCAO is highly accelerated rates of both bone formation and bone resorption, with higher rate of formation than that of resorption, which occur in general skeletal leading to the diffuse osteosclerosis with severe bone pains.

  • Steroid therapy including intravenous pulse administration in our patient evidently ameliorated his bone pains and reduced elevated values of bone markers. This was the first successful treatment for HCAO among cases reported so far and seemed to propose a key to solve the question for its pathogenesis.

  • The speed of increase in the bone mineral content of the patient was very high, suggesting that clarification of the mechanism(s) might lead to the development of a novel therapy for osteoporosis.