A Case of Palpable Purpura Associated With Japanese Spotted Fever

This report presents the case of a 90-year-old man with Japanese spotted fever (JSF), caused by Rickettsia japonica, who initially manifested high fever, rash, eschar, and lymphadenopathy. After successful antibiotic therapy, he developed palpable purpura similar to IgA vasculitis (IgAV). Previous reports indicate that the rash in spotted fever group of rickettsial infections, including JSF, undergoes a transformation from petechial spots after three to four days. However, in this case, the rash resolved completely after one week, and on day 10 of hospitalization, new purpura with palpable infiltration developed, leading to the consideration of IgAV. A skin biopsy and direct immunofluorescence assay revealed findings that suggested IgAV. IgA elevation was observed in the blood test. IgAV has been reported to be caused by various factors, including bacterial and viral infections, vaccines, and medications, and solid-organ malignancy is recognized as a risk factor. Although this patient was elderly, there were no serious underlying conditions. While there were no regular oral medications, minocycline and levofloxacin were used for rickettsiosis treatment; however, no association between these two agents and IgAV development has been reported. This case suggests that JSF may have triggered secondary IgAV, emphasizing the need for clinicians to consider IgAV when palpable purpura develops after treatment for rickettsial infection.