Question

A patient presents with the fever Arthritis and a Salmon coloured rash on the trunk laboratory findings show decreased CD 25 expression. What is the most likely diagnosis?

• A. Adult-onset still’s disease
• B. Systemic lupus erythematosus
• C. Systemic juvenile idiopathic arthritis
• D. Hemophagocytic lymphohistiocytosis

Hint:

Yamaguchi criteria for AOSD require major criteria: Fever $\geq$ 39°C for $\geq$ 1 week, Arthralgia $\geq$ 2 weeks, typical salmon-colored rash, and leukocytosis ($>$10,000 with $>$80% PMNs). A massively elevated ferritin level is a key board clue.

Answer 1

The Correct Option is A

Concept:
The classic triad of high spiking (quotidian) fever, arthritis, and an evanescent salmon-colored maculopapular rash on the trunk and extremities describes Still's disease.
When occurring in a patient over 16 years of age, it is termed Adult-Onset Still's Disease (AOSD).
Explanation:

• Adult-Onset Still's Disease (AOSD) is a rare systemic autoinflammatory disorder. It is characterized by high spiking fevers (often peaking late in the day), a fleeting salmon-colored rash that appears with the fever, polyarthritis, sore throat, and marked hepatosplenomegaly or lymphadenopathy.

• Laboratory findings typically show extremely high serum ferritin levels ($>$1000 ng/mL, sometimes highly glycosylated).

• A severe, life-threatening complication of AOSD is Macrophage Activation Syndrome (MAS), a form of secondary Hemophagocytic Lymphohistiocytosis (HLH). In active AOSD and impending MAS, natural killer (NK) cell function is profoundly impaired.

• The question mentions "decreased CD25 expression". In AOSD, CD25 (the alpha chain of the IL-2 receptor) can be discussed in two contexts: soluble CD25 (sCD25) is typically elevated as a marker of T-cell and macrophage activation. However, reduced expression of CD25 on specific regulatory T-cells or reduced NK cell function is part of the pathogenesis allowing macrophage hyperactivation. Irrespective of the exact nuance intended by the question's recall of "decreased CD25", the clinical triad (fever, arthritis, salmon rash) is universally pathognomonic for Still's disease.

• Option (C), Systemic JIA, has the exact same clinical presentation but applies to children under 16. "Adult-onset" is selected based on the implication of an adult patient (as it's listed distinct from JIA).

• Option (D), HLH, can be a complication, but the rash and arthritis denote the underlying primary disease (AOSD).
Final answer:
The pathognomonic triad of daily spiking fever, arthritis, and salmon-colored rash defines Adult-Onset Still's Disease.