Rosh Pediatrics Practice Exam

What is the most likely diagnosis for a child presenting with a circular ring-like rash on the ankle?

1. Granuloma annulare

2. Lichen planus

3. Pyogenic granuloma

4. Tinea corporis

The correct answer is: Granuloma annulare

The presentation of a circular ring-like rash on the ankle is highly indicative of granuloma annulare, making this the most likely diagnosis. Granuloma annulare typically manifests as a ring-shaped rash that can vary in size and is often skin-colored or reddish. It's most commonly found on the extremities, including the ankles, where it can easily be mistaken for other dermatoses. This condition is generally benign and self-limiting, and while the precise etiology is not fully understood, it is thought to possibly relate to an immune response that is non-infectious. In clinical practice, recognition of this characteristic "annular" pattern is key to distinguishing it from other skin conditions. In contrast, tinea corporis would usually present with a more well-defined border and is often scaly due to the fungal infection, lichen planus typically presents with flat-topped, shiny lesions that may have a violaceous hue, and pyogenic granuloma usually appears as a reddish, dome-shaped lesion that bleeds easily. Each of these conditions has defining features that differentiate them from granuloma annulare, reinforcing why the ring-like rash described is most consistent with granuloma annulare.