Case 164. 
Non-tuberculous mycobacterial infection of skin (43 y-o M)
    Biopsy from a scaling skin nodule on the dorsum of the hand of a tropical fish seller    
Key words : 
Mycobacterium marinum, non-tuberculous Mycobacterium, swimming pool granuloma, Mycobacterium avium, Mycobacterium ulcerans, Buruli ulcer    
A dark red-colored, irregularly elevated infiltrative lesion is seen on the dorsum of the hand (gross findings). This lesion has a nickname of swimming pool granuloma.   Histologically, non-caseous epithelioid granuloma is formed in the dermis (HE). Fibrotic scarring is associated. Infection of Mycobacterium marinum was confirmed by PCR analysis.
Reference case 164A
Skin biopsy of non-tuberculous mycobacterial infection in the chest wall of 7 y-o male, showing xanthogranulomatous reactions with Langhans-type giant cells (HE). Infection by Mycobacterium avium is confirmed by culture. The histologic features somewhat resemble those of lepromatous leprosy.
  Reference case 164A
Ziehl-Neelsen stain reveals numerous acid-fast bacilli in the cytoplasm of foamy histiocytes. This type of non-tuberculous mycobacteriosis tends to be clustered within a family. M. avium can grow in 42℃ water, and the 24-hour bath system can be equipped in the house. This is the reason why the incidence of cutaneous M. avium infection is increasing in Japan.
Reference case 164B
Buruli ulcer (large painless ulcer) caused by Mycobacterium ulcerans, seen in the leg of a Kenyan adult (HE). Diffuse coagulative necrosis is formed in the dermis though subcutaneous tissue. Undermining ulceration is characteristic. No granulomatous reaction is seen.
  Reference case 164B
Ziehl-Neelsen stain reveals numerous clumps of acid-fast bacilli among the subcutaneous fat cells. The acid-fast bacilli often form globular structures in the necrotic tissue. They are extracellular in location. The disease is seen mainly in the central and west Africa.