Cutaneous Mycobacterial Infections
Cutaneous mycobacterial infections present in diverse ways, often requiring suspicion based on exposure history and the presence of granulomatous inflammation.
Key Mycobacterial Conditions
| Condition | Pathogen | Clinical Presentation |
|---|---|---|
| Lupus Vulgaris | M. tuberculosis | Reddish-brown “apple-jelly” nodules; chronic/progressive. |
| Swimming Pool Granuloma | M. marinum | Solitary nodule/ulcer, often on hands, after water exposure. |
| Leprosy (Hansen’s) | M. leprae | Hypopigmented macules with loss of sensation. |
Clinical Management Pearls
- Lupus Vulgaris: Represents re-infection in a previously sensitized individual. “Apple-jelly” color on diascopy is pathognomonic.
- M. marinum: Characteristically follows a sporotrichoid spread (nodules appearing along lymphatic drainage). Always ask about aquarium or pool exposure.
- Diagnosis: Histopathology showing tuberculoid granulomas is common; tissue culture (at 30-32°C for *M. marinum*) is essential.
High-Yield Exam Pearl:
- Leprosy Diagnosis: The diagnosis is clinical, focusing on the anesthetic nature of the skin lesions and peripheral nerve thickening.
- Diascopy: Use a glass slide to press on the lesion; if it turns a “golden-yellow” (apple-jelly) color, it strongly suggests a granulomatous process like Tuberculosis or Sarcoidosis.