American Board of Internal Medicine (ABIM) Certification Practice Exam

Which organism is closely associated with the 'sporotrichoid' appearance due to ascending lymphatic spread?

1. Francisella tularensis

2. Mycobacterium fortuitum

3. Mycobacterium marinum

4. Salmonella

The correct answer is: Mycobacterium fortuitum

The 'sporotrichoid' appearance is typically characterized by the formation of nodular lesions that follow along the lymphatic pathways, resembling the classic presentation of cutaneous sporotrichosis. This pattern is closely associated with Mycobacterium marinum, which is known to cause a similar lymphatic spread in the setting of contaminated water exposure, often linked to aquarium handling or fish encounters. Mycobacterium fortuitum, while also a non-tuberculous mycobacterium, is not primarily recognized for producing a sporotrichoid pattern. Instead, it can lead to skin infections post-surgery or after trauma, but these do not commonly exhibit a specific lymphatic pattern like the sporotrichoid appearance characteristic of Mycobacterium marinum. This understanding highlights the importance of recognizing the distinct clinical manifestations associated with various organisms. In this case, knowledge about the typical presentations of mycobacterial infections aids healthcare providers in diagnosing and managing these conditions effectively.