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The aetiology of adult onset Still's disease remains unknown although some authors have tried to relate it to a viral infection.1-10 We describe here a case of typical adult onset Still's disease with a seroconversion in the rubella antibody titre to emphasise that it is probably more than a coincidental event.
A 26 year old woman was admitted because of fever with chills, a pruritic rash, myalgia, sore throat and headache. At the time of physical examination the temperature was 40°C and the pulse rate 104 beat/min. The rash consisted of small pruritic macules over back, periorbicular, legs and arms. The pharynx was erythematous. Some small cervical lymphadenopathies were detected. The leucocyte count was 42.3 × 109 cells/l (93.2% neutrophils) and the haemoglobin concentration was 79 g/l. Liver enzymes were slightly increased, aspartate aminotransferase (AST) 0.80 μkat/l and alanine aminotransferase (ALT) 0.73 μkat/l, but increased to AST 11.77 μkat/l and ALT 7.68 μkat/l after acetylsalicylic acid administration. Lactate dehydrogenase was 17.33 μkat/l. The serum albumin concentration was 26 g/l and the erythrocyte sedimentation rate 60 mm 1st h. The serum ferritin was higher than 1500 μg/l (normal value: 20–250 μg/l). Roentgenogram of chest and urine analysis were normal as well as blood and urine cultures. Abdominal computed tomography showed hepatosplenomegaly. An electromyographic study was normal. Tests for antinuclear antibodies and rheumatoid factor were negative. Serum concentrations of immunoglobulins and complement were normal. Serological tests for hepatitis A, B or C, cytomegalovirus, parvovirus B19, human inmunodeficiency virus 1 and 2, Epstein-Barr virus, Mycoplasma, Treponema pallidum, Borrelia burgdorferi, Toxoplasma, Salmonella, Brucella, Legionella, Coxiella burnetti, Chlamydia and Rickettsia conorii were negative. The initial rubella IgG antibody titre was 140 000 IU/l.
During admission the patient looked acutely ill. Temperature rose to 40ºC every evening with chills. The patient developed swelling and tenderness of proximal interphalangeal joints, elbows, wrists and knees. Roentgenograms of joints were normal. Because of cough a new chest roentgenogram was made. It showed a right basal lobe alveolar infiltrate that resolved spontaneously in 72 hours.
At this point, our patient fulfilled the criteria of Yamaguchi for adult onset Still's disease.11 Initially, she was treated with acetylsalicylic acid 4 g/day by mouth, which had to be stopped because of an increase in liver enzymes, so prednisone 1 mg/kg/day orally was given with no improvement. Two weeks after admission methotrexate was added to diminish arthritis. The dose achieved was 7.5 mg by mouth weekly. The patient was discharged feeling well after staying in hospital for 34 days. At this moment rubella IgG antibody titre rose to 660 000 IU/l.
Our patient fulfilled Yamaguchi's criteria for adult onset Still's disease so this diagnosis was well established.11 12There was also strong evidence for acute rubella infection because the IgG antibody titre increased more than fourfold the initial one. It has been shown that children with primay rubella infection developing Still's disease increase both rubella IgG and IgM antibody titres.13 In our case we think that rubella was more probably attributable to a reinfection than to a primary infection because the patient had been correctly vaccinated in childhood and this is also supported by the increase in IgG antibody titre without increase in IgM concentrations.14 Moreover this seroconversion is not explained by a non-specific polyclonal stimulation after a generalised inflammatory disease because there was no increase in other measured antibody titres.
Although aetiology of adult onset Still's disease is unknown, some authors have tried to demonstrate that infective agents, especially viruses, can be the trigger of the illness in susceptible patients. In this way, echovirus 7,1 mumps,2cytomegalovirus,3-5 parainfluenza,3Epstein-Barr virus,3-5 influenza A,4parvovirus B19,6 hepatitis B or C7 8 and rubella1 3 9 10 have been associated.
The relation between rubella virus and adult onset Still's disease has been reported in some series and case reports1 3 9 10since the initial description by Bywaters in 1971.15Wouters et al performed exhaustive virological studies in five patients with adult onset Still's disease in an early phase of the illness and found evidence of viral infection in three cases, two of them corresponding to rubella.1 The rubella virus genome has also been detected in peripheral blood cell population from patients with adult onset Still's disease.16
In summary, we think that the increased rubella IgG antibody titre in our patient should not be considered an anecdotal event and probably rubella virus has been the trigger of the illness. Our case, together with previously published reports,1-10supports the hypothesis about the role of viruses in the aetiopathogenesis of adult onset Still's disease.
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