42 year old male with history of alcoholism and chronic tophaceous gout on allopurinol, presented with acute left elbow pain and swelling. Exam showed synovitis of left wrist and elbow, distal interphalangeal joint (DIJ) and right knee and tophi on left DIJ. Arthrocentesis of left elbow revealed purulent fluid with leukocytosis (5000,000/mm3) and MSU crystals with negative culture. Uric acid level was 10.1mg/dl with peripheral leukocytosis(16,000/mm3). His joint pain improved with antibiotics and steroids. On second day of admission tender nodular eruptions were noticed over extensor surfaces of distal lower extremities. Chalky while amorphous material was expressed from these lesions and biopsy showed evidence of acute suppurative panniculitis with presence of eosinophils. Prednisone therapy was continued with improvement in skin lesions and joint pain.
Discussion:
Gout is a form of inflammatory arthritis caused by defective uric acid metabolism and deposition of mono sodium urate (MSU) crystals in joints, bones and soft tissues. Untreated gout can lead to tophi and destructive arthropathy. Tophi forms in the joints, cartilage and bones and rarely reported in sclera, nose, heart valves, breasts, abdominal striae, and subcutaneous skin. Panniculitis is a very rare manifestation of gout.
Gouty panniculitis is a non-vasculitic inflammation of the hypodermis, predominantly in the lobular hypodermis (even though mixed lobular and septal inflammation can occur) due to MSU deposition. Histologically, amorphous eosinophlic material and foreign body granulomas can also be seen. Skin lesions can occur before, concomitantly or even years after the onset of gout. Clinically it presents with erythema, induration and tender nodules with tendency to ulcerate and drain opaque or serous MSU rich fluid. Underlying mechanism is still unknown. One proposed mechanism is localized inflammation and tissue injury from disruption of arterial blood supply or micro trauma to terminal capillary walls in dermis and adipose tissue by MSU crystal deposition. Uric acid levels can be variable in these patients. Definitive diagnosis can be made only by biopsy of the lesions. There is no specific therapy for gouty panniculitis due to lack of experience and rarity of this entity. Several case reports suggested long term therapy with high doses of allopurinol (600-1200mg/day) or short duration of low dose corticosteroids (prednisone 30-60mg) as inital treatment.
Conclusions:
Panniculitis is a very rare manifestation of gout. Since gouty panniculitis is a rare entity, it can often be overlooked. Thus in the right clinical setting it is important to include it in the differential to guide further management. Low dose corticosteroids with long term high dose allopurinol can be used as the first line of therapy for gouty panniculitis.