Case 168. Tsutsugamushi disease (38 y-o M)
    Autopsy findings of the skin and heart in a classic Tsutsugamushi disease in Akita (clinical course: 8 days)    
Key words : Orientia tsutsugamushi, Tsutsugamushi disease, scrub typhus
At the site of Tsutsugamushi (mite) bite (eschar), necrotic ulceration is formed (HE, low power). The inflammation extends to the subcutaneous tissue.   At the base of skin ulcer, phagocytizing macrophages are clustered. Fine granules can be recognized in the cytoplasm of the macrophages (HE, oil immersion).
The heart muscles are multifocally infiltrated by lymphocytes and macrophages (HE). The features are consistent with rickettsial myocarditis.   Reference case 168A
The eschar (the site of mite bite) in Tsutsugamushi disease (scrub typhus). Identification of the eschar (tache noire), a crusted ulcer of the skin, is a clue for the appropriate diagnosis of this rickettsiosis.
Reference case 168A
Biopsy of the eschar, showing necrotizing ulceration with extensive inflammatory infiltration (HE). Classic Tsutsugamushi disease was endemic to the certain areas of Japan, including Akita, but the new type disorder is seen widely not only in Japan but also in Asia and Australia.
  Reference case 168A
Ulcer base of the eschar (HE, higher power). Infiltration of phagocytizing macrophages and small lymphoid cells is observed. This lady patient was active in visiting mountainous areas in late autumn.
Reference case 168A
Immunostaining using a 1:500 diluted patient's own serum shows granulated positivity in the macrophages located at the ulcer base (indirect immunoperoxidase). Infection of Rickettsia or Orientia occurs mainly in the endothelial cells of the capillary vessels.
  Orientia tsutsugamushi growing in mouse abdominal macrophages (Giemsa)
Fine granularity is discerned in the cytoplasm of the infected macrophages. The pathogen is a small, Gram-negative obligate intracellular bacterium.