Adult-Onset Still’s Disease: Key Facts, Diagnosis & Treatment

Authoritative facts from DermNet New Zealand about Adult-onset Still’s disease — a rare systemic inflammatory disorder.

What is adult-onset Still’s disease?

Adult-onset Still’s disease (AOSD) is a rare autoinflammatory or autoimmune disorder characterized by high spiking fevers, an evanescent salmon-pink rash, arthralgia or arthritis, and systemic inflammation affecting multiple organs. It shares clinical features with systemic-onset juvenile idiopathic arthritis (Still’s disease in children) but occurs in adults typically aged 16–35 years, affecting men and women equally. AOSD is considered systemic due to its potential to involve the skin, joints, muscles, lymph nodes, liver, spleen, lungs, and pericardium.

The precise cause remains unknown, but research suggests it may be triggered by infections in genetically susceptible individuals, leading to an exaggerated immune response. Unlike rheumatoid arthritis, AOSD lacks specific autoantibodies such as rheumatoid factor or antinuclear antibodies.

Who gets adult-onset Still’s disease?

AOSD is rare, with an estimated incidence of 0.16–0.4 cases per 100,000 people annually. It most commonly affects young adults aged 16–35 years, though cases occur across all adult age groups. There is no gender predominance, unlike some other inflammatory arthritides. Risk factors include genetic predisposition (e.g., HLA associations) and possible environmental triggers like viral infections.

• Peak incidence: 16–35 years
• Incidence: <1 per 100,000/year
• Prevalence: Unknown, but very rare

Clinical features

Patterns of disease

AOSD exhibits three main clinical patterns based on progression:

• Monophasic: Single episode lasting weeks to <1 year (∼30% of cases)
• Polyphasic/intermittent: Recurrent flares with symptom-free intervals (weeks to years); later flares often milder (∼30–40%)
• Chronic: Persistent symptoms, often evolving to chronic arthritis (∼30–40%)

Symptoms and signs

Symptoms develop abruptly or gradually, often starting with high fever and sore throat.

• Fever: quotidian (daily) or double-quotidian spikes to ≥39°C (102.2°F), typically afternoon/evening, lasting ≥1 week
• Rash: Evanescent (comes/goes with fever), non-pruritic salmon-pink maculopapular eruption on trunk, proximal limbs; may involve palms/soles; koebnerization possible
• Joint involvement: Symmetric polyarthritis/arthralgias (knees, wrists, ankles, elbows, PIPs); lasts ≥2 weeks; may migrate or persist
• Sore throat: Common early symptom; pharyngitis without exudate
• Lymphadenopathy: Generalized tender nodes
• Hepatosplenomegaly: Frequent
• Myalgias: Muscle pain, fatigue
• Other: Weight loss, serositis (pleuritis/pericarditis), abdominal pain

Complications

Untreated AOSD can lead to joint destruction, amyloidosis, and macrophage activation syndrome (MAS; ∼10–15% risk, life-threatening cytokine storm).

• Joint damage in chronic cases
• MAS: High ferritin, coagulopathy, multiorgan failure
• Rare: Pneumonitis, myocarditis

Diagnosis

No single diagnostic test exists; diagnosis relies on clinical criteria after excluding mimics (infections, malignancies, other rheumatologic diseases).

Yamaguchi criteria (most sensitive/specific)

Major (5 required, ≥2 must be excluded):

• Fever ≥39°C ≥1 week
• Arthralgias ≥2 weeks
• Typical rash
• Leukocytosis ≥10,000/μL (≥80% granulocytes)

Minor:

• Sore throat
• Lymphadenopathy/hepatosplenomegaly
• Liver dysfunction
• Negative ANA/RF

Fautrel criteria (ferritin-focused)

Emphasizes glycosylated ferritin <20% and ferritin >1000 ng/mL.

Investigations: Exclude infections (cultures, serologies), malignancy (imaging, biopsy), other rheumatologic diseases (ANA, RF negative).

Differential diagnosis

• Infections (viral: EBV, CMV; bacterial endocarditis)
• Malignancy (lymphoma)
• Other autoinflammatory (SJIA, Kikuchi disease)
• Rheumatologic (SLE, RA, vasculitis)
• Drug reactions

Treatment

Treatment is guided by disease pattern/severity; aim for rapid control to prevent complications.

• First-line: NSAIDs for mild disease
• Second-line: Glucocorticoids ± methotrexate
• Biologics: Excellent response (70–90%) to IL-1 (anakinra) or IL-6 (tocilizumab) inhibitors

Disease course and prognosis

Variable: 30% monophasic (good prognosis); 40% polyphasic; 30% chronic with destructive arthritis. Early aggressive therapy improves outcomes, reduces joint damage risk. Mortality ∼2–5% (MAS, infection, amyloidosis).

Frequently asked questions (FAQs)

Q: Is adult-onset Still’s disease curable?

A: Not curable, but many achieve remission with treatment; monophasic cases often self-resolve.

Q: What does the AOSD rash look like?

A: Evanescent salmon-pink macules/papules on trunk/limbs, coinciding with fever spikes.

Q: Can AOSD be fatal?

A: Rarely (∼2%), usually due to MAS or complications.

Q: How is AOSD diagnosed?

A: By Yamaguchi/Fautrel criteria + exclusion of mimics; high ferritin key.

Q: What are the best treatments for AOSD?

A: NSAIDs/mild; steroids + biologics (IL-1/IL-6 inhibitors)/severe.

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Medha Deb is an editor with a master's degree in Applied Linguistics from the University of Hyderabad. She believes that her qualification has helped her develop a deep understanding of language and its application in various contexts.

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