Case 169. Japanese spotted fever (38 y-o F)
    Hemorrhagic skin spots on the trunk and extremities in a Tokushima resident presenting high fever and thrombocytopenia (biopsy from the leg)    
Key words : Rickettsia japonica, Japanese spotted fever
The eschar (the site of mite bite) in Japanese spotted fever is smaller than in Tsutsugamushi disease (gross findings). Rickettsia japonica is transmitted by a larva of the tick Hamoaphysalis flava.   The skin rash is often hemorrhagic and predominantly seen on the extremities. The transmission occurs during the summer season. These make points of difference from Tsutsugamushi disease.
Histologic features of skin rash are nonspecific. Perivascular infiltration of small lymphocytes and some plasma cells is seen in the entire thickness of the dermis (HE, low power).   High powered view shows nonspecific lymphocytic infiltration around small vessels (HE). This emerging rickettsial disorder was discovered by Dr. Fumihiko Mahara in Tokushima in 1984.