Hypertrophic osteoarthropathy secondary to thymoma: rare presentation in childhood

Hypertrophic osteoarthropathy (HOA) is a group of syndromes characterized by clubbing, polyarthritis, and periosteal reaction. It is usually secondary to thoracic tumors and is extremely rare in children, therefore is easily to be misdiagnosed and delayed. In this study, we present an 11-year-old boy hospitalized because of joint swelling and pain accompanied by obvious clubbing, and was finally diagnosed as HOA secondary to thymoma. Heart Doppler ultrasound and blood gas analysis ruled out the existence of heart and lung function abnormal. Knee and ankle joint MRI supported the diagnosis of HOA. The radionuclide bone scan of the boy presented no other specials except for active bone metabolism on the left upper jaw bone. X-ray showed apparent periosteal reactions, which support the diagnosis of HOA. Thoracic CT showed space occupying lesion in anterior mediastinum and supraclavicular site and biopsy indicated that he was with thymoma (type B2). During the admission, routine symptomatic and anti infection treatment was applied. The parents finally give up further treatment and the patient discharged. Follow-up showed that the boy was died at home six months after left the hospital. To our knowledge, this is the first case of HOA secondary to type B2 thymoma in child. We intend to further improve our understanding of hypertrophic osteoarthritis by studying this case.