A case of arthritis and panniculitis - an unusual manifestation of a common disease.

Sir,

A 42-year-old gentleman presented with episodic arthritis involving large and small joints for 4 years. He had painful erythematous nodular lesions over the anterior aspect of the shin of both lower limbs with a history of whitish discharge from the lesions intermittently [Figure 1a]. He used to have relief of pain with nonsteroidal anti-inflammatory agents. He was a known hypertensive with blood pressure of 150/100 mmHg and obese with a body mass index of 28 kg/m2 at presentation. On evaluation, he was found to have negative rheumatoid factor and anticyclical citrullinated peptide (1 RU/mL), elevated C-reactive protein (26 mg/L) and elevated uric acid level (11.3 mg/dL). Radiographs of hands including the wrists and knee joint were normal. Ultrasound of the knee was done which showed double contour sign of the femoral cartilage suggestive of a uric acid deposition disease [Figure 1b]. Histopathological examination of skin nodules was done, which showed focal areas of necrosis and eosinophilic feathery material deposits within the fat lobules admixed with infiltrates of neutrophils and macrophages with needle-like spaces within the eosinophilic material [Figure 1c and d]. Microbiological evaluation of the skin biopsy specimen was negative for infections. A diagnosis of gouty arthritis with panniculitis was made and was started on tablet febuxostat 40 mg once daily and colchicine 0.5 mg twice daily, with which he had improvement in his joint pain and decrease in the skin nodules after 1 month. Gouty panniculitis is a rare manifestation of gout characterized by the deposition of monosodium urate crystals in the subcutaneous tissue fat lobules. There are only a few cases described in literature.[1] Increased serum uric acid levels lead to oversaturation of monosodium urate with deposition in joints and/or subcutaneous tissue. The deposition may be precipitated by other factors like varicosities, chronic edema related to cardiac failure, and elevated serum amylase or lipase, which may damage the subcutaneous tissue.[1] The differential diagnosis of gouty panniculitis encompasses a wide range of disorders including sclerema neonatorum, subcutaneous fat necrosis, pancreatic panniculitis, post steroid panniculitis, factitial panniculitis, connective tissue associated panniculitis and lymphomas. The histopathological examination of gouty panniculitis often shows granulomatous reaction but rarely can demonstrate the detection of feathery crystalline material.[2] Since monosodium urate crystals can be dissolved during paraffin fixation[3] needle-shaped empty spaces represent the crystals of monosodium urate. Thus, the direct detection of crystals from tissues can be done by either ethanol fixation or by touch imprint slides from fresh tissue using polarizing microscopy. Although no clear guidelines for treatment exist, the biological basis for treatment remains the same. Urate lowering therapy, with anti-inflammatory therapy, has shown a good response in various reports.[45] Our patient had an excellent response to colchicine and urate-lowering therapy within a month of initiation of medications.

Figure 1

(a–d): (a) Erythematous nodular painful lesions over the anterior aspect of legs. (b) Longitudinal scan of the left knee showing femoral cartilage with double contour sign showing uric acid crystal deposition. (c and d) Feathery eosinophilic crystalline material and surrounded by palisading histiocytes (arrows show the histiocytes in (c)). Needle-like spaces within the eosinophilic material are suggestive of gout, although the deposited urate crystals have been dissolved during routine processing (1c: H and E, 40×, 1d: H and E, 10×)

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