Adult-onset Still’s disease (AOSD) is a systemic autoinflammatory disorder characterized by persistent fever at regular intervals, arthralgias or arthritis, rash, sore throat and neutrophilic leukocytosis.1,2 Significant elevation in ferritin levels is characteristic and tends to correlate with disease activity. Additional clinical features may include myalgias, lymphadenopathy, hepatosplenomegaly, serositis, myocarditis, abnormal liver function tests and development into potentially life-threatening macrophage activation syndrome (MAS).3
The diagnosis of AOSD poses challenges due to the nonspecific clinical features and the lack of specific diagnostic tests. Alternative diagnoses, including infections, drug reactions, malignancies and systemic rheumatic diseases, such as systemic lupus erythematosus and vasculitis, must be excluded. Various classification criteria have been suggested, and Yamaguchi criteria are commonly used to aid in classification (see Table 1).2,3
The typical AOSD rash is an evanescent, salmon-colored, maculopapular rash that often accompanies a fever and is seen in up to 80% of patients.3 However, an under-recognized, atypical rash that presents as persistent pruritic plaques or papules on extremities and torso, mimicking dermatomyositis, may also be found in a subset of patients with this disorder.4–10 This rash demonstrates distinctive features on histology, including parakeratosis, dyskeratosis and necrotic keratinocytes in the upper half of the epidermis and, if recognized, can facilitate an earlier diagnosis.4,6
Here, we report on a patient with AOSD and distinctive skin biopsy features consistent with the atypical (persistent) eruption of AOSD preceding a diagnosis of breast cancer.
FIGURES 1A, 1B & 1C (above): Persistent hyperpigmented plaques on the chest and neck, upper lateral arm and back. (Click to enlarge each.)
Case Presentation
A 28-year-old woman presented with a three-week history of migratory arthralgias and myalgias, daily fevers up to 103ºF (39ºC) and a diffuse pruritic rash on her arms, legs, chest and back. Prior to admission, she presented to an outside emergency department and an urgent care facility five times within one month with similar symptoms and was diagnosed with a viral syndrome.
Tests for respiratory viral infections, including influenza and COVID-19, were negative. She took non-steroidal anti-inflammatory drugs (NSAIDs) with minimal relief of her arthralgias and myalgias. On admission, she was febrile to 38.5ºC, tachycardic to 112 beats per minute and hypertensive at 143/91 mmHg. Auscultation of the heart did not reveal any murmurs, gallops or rubs, and lung auscultation revealed vesicular breath sounds without rales, rhonchi or wheezes. Her skin exam revealed lichenified hyperpigmented plaques (see Figures 1 & 2) on her upper arms, back, around her neck and on her upper chest and legs, with excoriated areas concentrated on extensor surfaces, grossly normal nailfolds, normal muscle strength and diffuse joint tenderness without synovitis.
