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ESSENTIALS OF DIAGNOSIS

  • Quotidian fever, frequently greater than 39°C.

  • Evanescent, salmon-colored macular rash on the trunk and extremities, often coincident with fever spikes, typically in the late afternoon or evening.

  • Other main clinical features are pharyngitis, polyarthralgia, lymphadenopathy, splenomegaly, and serositis.

  • Common laboratory abnormalities include a leukocytosis, elevations of the acute phase reactants (erythrocyte sedimentation rate and C-reactive protein), and dramatic increases in the serum ferritin level.

  • The most striking complication of adult-onset Still disease (AOSD) is reactive hemophagocytic lymphohistiocytosis (RHL), formerly named macrophage activation syndrome.

GENERAL CONSIDERATIONS

Adult-onset Still disease (AOSD) is a rare systemic inflammatory disease of unknown etiology. Its reported incidence varies between 0.16 and 0.4 cases per 100,000. The sex ratio varies between 0.5 and 0.7, slightly in favor of women. By definition, AOSD begins after the age of 16 years and tends to affect young adults. The condition occurs after the age of 35 years in only one-quarter of patients and rarely in the elderly.

Patients with AOSD share many clinical similarities with patients who have systemic-onset juvenile idiopathic arthritis (SoJIA), and it is likely that there exists a continuum between these two entities. Common autoinflammatory mechanisms involving inflammatory cytokines such as interleukin (IL)-1-β, tumor necrosis factor-alpha (TNF-α), IL-6, IL-8, IL-18 are operative in both. AOSD has two main clinical presentations (articular form with arthritis at disease onset, and systemic form), and several potential evolutions, including monocyclic, polycyclic, and chronic forms. Its diagnosis is one of exclusion.

CLINICAL FINDINGS

The classic patient with AOSD has a presentation with four cardinal features: spiking fever, arthralgias, a salmon-pink evanescent maculopapular rash, and peripheral blood leukocytosis.

A. Symptoms and Signs

1. Fever and general signs

The fever of AOSD typically occurs daily, with temperature elevations to greater than or equal to 39°C (sometimes up to 41°C), in the late afternoon or evening. The fever recurs each day with profound sweating and shaking chills that disappear hours later when the temperature returns to normal, even in the absence of antipyretic medications. In some cases, two spikes can be observed daily with a return to normal temperatures in between. In others, however, a low-grade baseline fever persists between spikes. It may therefore present as a prolonged fever of unknown origin and is resistant to antibiotics. General symptoms of fatigue, weight loss, and anorexia accompany the fevers. Patients inevitably endure detailed evaluations for possible infections and malignancies, with multiple cultures, imaging studies, and biopsies (eg, of lymph nodes, liver, and bone marrow) before diagnostic considerations turn to AOSD.

2. Rash

The rash, typically salmon-colored and macular or maculopapular, usually affects the trunk and extremities, sparing the face, palms, and soles (Figure 14–1). The rash is usually asymptomatic and may not be ...

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