Adult onset Still's disease: Role of scintigraphy

INTRODUCTION

Adult onset Still's disease (AOSD) is a rare systemic inflammatory disorder of unknown etiology, characterized by quotidian or double quotidian spiking fevers with an evanescent rash, arthritis, and multi-organ involvement. It was first described by Eric GL Bywaters in 1971, with description of 14 patients.[1]

CASE REPORT

A 21-year-old female patient presented with fever of high grade, recurrent and intermittent in character, associated with severe sore throat. She was extensively investigated for possible infectious disease. She received antibiotics and antimalarial drugs without any response. Physical examination revealed pallor, hepatomegaly. Investigations revealed hemoglobin of 9.7 g/dL, polymorphonuclear leukocytosis total leukocyte count (TLC 17500/mm³ with 92% neutrophils), thrombocytosis (platelet count 848000/mm³), a markedly raised erythrocyte sedimentation rate (ESR) (45 mm in the 1^st hr by Westergren method), negative anti-nuclear antibodies (ANAs), and rheumatoid factor (RF). Serum Ferritin levels were high >13,000 ng/ml. Computed tomography thorax was normal. X-ray of the hands was within normal limit. Liver function tests revealed serum total bilirubin 0.8 mg/dL, serum direct bilirubin 0.45 mg/dL, Serum glutamic pyruvic transaminase/ Alanine transaminase (SGPT/ALT) 31.5 IU/L.

In view of the presence of characteristic fever, sore throat, polyarthritis, markedly raised ESR, leukocytosis, and the absence of ANAs and RF, diagnosis of (AOSD) was made.[2] She was treated successfully with Prednisone (20 mg).

Tc99m-phytate liver scan [Figure 1] and Tc99m-Methylene diphosphonate (MDP) bone scan [Figure 2] were done for assessment of liver parenchymal function and arthritis respectively. Liver scan helped the physicians by making early diagnosis of onset of liver parenchymal dysfunction. Bone scan revealed polyarthritis with involvement of shoulder and hip joints indicating poor prognosis helping physicians to consider for aggressive management. Both the scans demonstrated their utility in early diagnosis of liver parenchymal dysfunction and arthritis pattern, prognostication of arthritis, and management respectively. The painful joints distinctly demonstrated increased uptake of 99mTc-MDP in scintigraphy.

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Figure 1 Tc99m phytate liver scan showed enlarged right lobe of liver with altered distribution of phytate with increased splenic and marrow uptake suggestive of early liver parenchymal dysfunction

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Figure 2 Tc99mmethyl diphosphonate-MDP bone scan showing bilaterally symmetrical arthritis in small and large joints of axial and appendicular skeleton

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DISCUSSION

AOSD is a systemic inflammatory disease. The classic presentation is the triad of persistent high spiking fever, joint pain, and a distinctive salmon-colored rash. The diagnosis is clinical and RF and ANA are classically negative and serum ferritin is elevated. Diagnosis requires the presence of all criteria in A and any two from B.

A (Major criteria) consist of (i) Fever > or = 39°C (ii) Arthralgia or arthritis RF < 1:80 (iii) ANA < 1:100.

B (Minor criteria) comprises (i) TLC > or = 15000/mm³ (ii) Still's rash (iii) Pleuritis or pericarditis (iv) Hepatomegaly or splenomegaly or generalized lymphadenopathy.

Our patient qualified for all criteria from A and two criteria from B. Tc99m-MDP bone scan was done to look for arthritis. Three-phase bone scan revealed bilaterally symmetrical inflammatory arthritis involving small and large joints of extremities.

Arthritis occurs in about 95%,[34] and flare-up of joint symptoms occurs during the febrile spike. As the duration of the disease increases, the arthritis becomes more prominent and the fever decreases in intensity. The most common joints involved are the knees, followed by the wrists, ankles, elbows, metacarpophalangeal, metatarsophalangeal, and distal inter-phalangeal joints, hips, neck, and temporomandibular joint and interphalangeal joints of the feet. Polyarthritis is most common. However, a few patients have oligoarthritis and rarely a single joint is involved. 5% of patients do not have arthritis.[3] About 18% have distal inter-phalangeal joint involvement. Bone scan evaluation may be useful in diagnosis of exclusion of arthritis analyzing arthritis pattern, use of disease modifying antirheumatic drugs (DMARD), non steroidal anti inflammatory drugs (NSAID), and steroids for polyarthritis, prognostication of arthritis. Polyarthritis in early disease, involvement of hip and shoulder are a sign of poor prognosis. Bone scan is also helpful in differentiating arthralgia or arthritis. Lymphadenopathy, splenomegaly, and hepatomegaly are detected in 63, 52, and 42% of patients respectively.[34] Close to 75% of patients have elevated liver enzymes. Although this might be due to drug toxicity (NSAIDS), in most patients, the abnormality seems to be primary 2. Liver biopsies have demonstrated mononuclear sinusoidal and portal tract infiltrates and mild Kupffer cell hyperplasia. Occasionally, focal hepatitis with feathery degeneration and necrosis of hepatocytes may be seen.[5]

Of the various acute phase responses, elevation of serum ferritin seems to be characteristic of AOSD. Marked hyper-ferritinemia is pathognomonic of AOSD. Levels of serum ferritin correlate with disease activity and have been used to monitor the same.[6] In this patient, serum Ferritin levels were high, >13,000 ng/mL. Liver function tests revealed serum total bilirubin 0.8 mg/dL, serum direct bilirubin 0.45 mg/dL, SGPT/ALT 31.5 IU/L. Phytate liver scan done for functional evaluation showed mild enlargement of liver and spleen. Mildly increased uptake of tracer was noted in enlarged spleen with minimal tracer uptake in marrow. Findings were suggestive of early changes of liver parenchymal dysfunction. Ultrasonography revealed mild hepatomegaly with normal echo texture. Deaths in AOSD are due to infection, amyloidosis, hepatic failure, acute respiratory distress syndrome, and disseminated intravascular coagulation. Liver scan helped in early diagnosis of liver parenchymal dysfunction, thus helping physicians in starting appropriate treatment. Bone scan in early course of disease and phytate liver scan to rule out hepatic parenchymal dysfunction can make an impact on patient management.