Question

Which condition does NOT feature granulomas?

• A. Mycoplasma pneumoniae
• B. Mycobacterium tuberculosis
• C. Mycobacterium leprae
• D. Yersinia enterocolitica

Hint:

TB, leprosy and Yersinia all form granulomas; Mycoplasma pneumoniae causes interstitial pneumonia without granuloma formation.

Answer 1

The Correct Option is A

Step 1: Recall what a granuloma is.
A granuloma is a tight cluster of activated macrophages, called epithelioid cells, often mixed with giant cells and a rim of lymphocytes. The body builds this wall when it cannot clear an antigen easily, usually in chronic infections.

Step 2: Go through each organism.
Mycobacterium tuberculosis is the textbook cause of caseating granulomas, the immune system tries to wall off the bacteria inside a cheesy, necrotic center. Mycobacterium leprae, in its tuberculoid form, also triggers well formed granulomas along nerves and skin as the immune system tries to contain the organism. Yersinia enterocolitica can inflame the terminal ileum and mesenteric nodes with granuloma formation, which is why it can be mistaken for Crohn disease or appendicitis on imaging and histology.

Step 3: Look at Mycoplasma pneumoniae separately.
This organism causes atypical, walking pneumonia. The lung shows an interstitial pattern of inflammation with lymphocytes and plasma cells lining the alveolar septa, not organized macrophage granulomas. There is no caseation and no giant cell wall building around the organism.

Step 4: Final answer.
The condition that does NOT feature granulomas is
\[ \boxed{\text{Mycoplasma pneumoniae}} \]