Lipid microspherule–associated acute monarticular arthritis

Abstract

We describe the fifth reported case of acute monairthritis associated with lipid microspherules. A 33-year-old obese man developed acute knee arthritis with a synovial fluid white blood cell count of 11,700/mm3 (97 % polymorphonuclear leukocytes). The fluid contained numerous strongly positively birefringent inltra-and extracellular spherules that measured 2-6 pm in diameter and had the appearance of Maltese crosses. No systemic lipid disorder or local trauma could accouint for the attack, which responded promptly to the administration of colchicine.In the differential diagnosis of acute monarticular arthritis, crystal-induced diseases, including gout and pseudogout, appear to be among the most frequent causes. Recently there have been 4 reported cases of acute monarthritis attributed to an unusual crystal, a liquid lipid microspherule (1,2). We wish to emphasize the potential pathogenicity of these crystals by de- scribing a fifth case and reviewing the evidence for their phlogistic potential. Case report. The patient, a 33-year-old, morbidly obese, mentally retarded black man, was otherwise well until 3 days prior to admission, when he complained of discomfort in his right knee. Increasing pain, which rapidly became severe, necessitated hospitalization. According to the patient and family, there was no history of trauma, fever, chills, gout, bleeding disorders, or any prior episodes of arthritis. He denied having pain in other joints. His medications included hydrochlorothiazide, 50 mg/day for hypertension, thioridazine, SO mg at bedtime, and perphenazine, 4 mg and amitriptyline, 25 mg each 3 times daily for intermittent agitation. There was no family history of rheumatic disease.On examination the patient was noted to be markedly obese and had moderate mental retardation. He was afebrile and had a pulse rate of 110 beats per minute, blood pressure of 130/90 mm Hg, and weight of 143 kg. There were no contusions or abrasions. The right knee was tensely swollen, slightly erythematous, and warm. There was full extension but only 30" of flexion, as compared with 110" of flexion in the left knee. All other joints had full range of motion without warmth, erythema, or tenderness.Laboratory investigation revealed a synovial fluid white blood cell count of 1 I ,900/mm3, with 74% polymorphonuclear leukocytes (PMNs). The hemoglobin level was 13.9 gm/dl, and the platelet count was 259,000/mm3. The serum uric acid level was 7.7 mg/dl (normal <8.5), and the cholesterol and triglyceride levels were 170 mg/dl and 81 mg/dl, respectively. The prothrombin time, activated partial thromboplastin time, electrolytes, amylase, lipase, and serum protein