These lesions become papular and petechial, and in untreated patients, the rash becomes purpuric and ecchymotic. Thrombosis of terminal arteries may lead to gangrene of the fingers, toes, nose, ears, or scrotum. The headache in adults and older children is severe, persistent, and often unresponsive to therapy with analgesics. Young children may not complain of headaches. Seizure, cortical blindness, central deafness, learning disability, ataxia, and spastic paralysis have been reported.
Myalgia is a common feature, and patients often have tenderness in the calf and thigh muscles.
Some of the other clinical manifestations of RMSF include DIC, shock, congestive heart failure, arrhythmia, edema of the extremities or face, conjunctival suffusion, jaundice, and hepatosplenomegaly. A definitive diagnosis of RMSF often cannot be made until the second week of the illness. It is imperative that the physicians make the diagnosis based on historical and clinical features and initiate specific therapy promptly prior to the laboratory confirmation of the disease. Rickettsia rickettsii can be identified during the early stages of the illness by immunofluorescence or immunoperoxidase staining of skin biopsy specimen of the rash. Culture of R. rickettsii is usually not attempted because of the danger of transmission to laboratory personnel.