P051 A rare mimic of inflammatory arthritis

Abstract

Abstract Background/Aims Rosai-Dorfman syndrome is a rare disorder, primarily affecting young males, characterised by overproliferation and accumulation of histiocytes. It commonly affects lymph nodes but can affect the nervous system, kidneys and skin. Bone involvement is rare (around 5%) and presents as lytic lesions. Diagnosis can be challenging as many cases spontaneously resolve. In severe cases steroids, radiotherapy or chemotherapy may be used. Methods We present a case of a 34-year-old gentleman with a 4-month history of fatigue, widespread arthralgia and unintentional weight loss. Pain was severe, nocturnal and involved joints and long bones. There was no joint swelling. He had recently had a self-limiting episode of headaches and night sweats that was presumed secondary to a viral infection. He had no rash and no features suggestive of connective tissue disease. He did not smoke or drink alcohol and had no recent travel history. His symptoms responded to NSAIDS but recurred quickly. Results On examination, he had a tender right elbow and tender bilateral tibia. There was no evidence of synovitis. He had no lymphadenopathy. X-rays of elbows and knees showed no effusion or erosions. Viral and autoimmune screens were negative. He had a normocytic anaemia with Hb 108. His CRP was rising at 57, having been 27 when initially referred; this was felt inconsistent with a reactive arthritis. LDH was normal along with normal WBC count. A PET-CT was requested to investigate for malignancy, this showed multiple foci of tracer uptake throughout the skeleton but no lymph node involvement. He was referred to haematology for tissue diagnosis and had two bone biopsies, one of which was suspicious for histiocytosis. A bone marrow biopsy showed non-necrotising histiocytic granulomas. Langerhan's Histocytosis was considered and a repeat PET arranged. This showed progressive increased uptake throughout the skeleton and bone marrow with new lytic lesions. There was tracer uptake in the skin, lung and kidneys, reported as possible Rosai-Dorfman disease. No evidence of primary malignancy was found after extensive investigations. He then developed frontal and occipital skin lesions. MRI head showed dural lesions, suspicious for meningioma. He was referred to dermatology for biopsy of skin lesions. However, the skin and dural lesions spontaneously resolved. This was associated with resolution of fatigue and arthralgia. His CRP settled to 2.8 and anaemia resolved 6 months after presenting. A diagnosis of spontaneously remitting Rosai-Dorfman disease was made in conjunction with the national histiocytosis advisory panel. He remains under surveillance. Conclusion This case highlights a rare presentation of a rare condition. As rheumatologists we often see cases which present a diagnostic challenge. Rosai-Dorfman disease has characteristic appearances on PET and should be considered as a diagnosis in patients with atypical joint pain and abnormal PET-CTs. Disclosure M. Cox: None. M.F. Kazmi: None.