Comments
INITIAL SYMPTOMS:
A skin lesion may be found at the site of the mite bite. Regional lymphadenopathy and later fever and rash occur. The vesicular rash has been mistaken for the rash of chickenpox. [CCDM]
EPIDEMIOLOGY:
Rickettsialpox is transmitted by mites from mice to people. The disease is prevented by controlling mice and their mites. Most cases have been reported in New York City and cities in the former Soviet Union. [CCDM, p. 520-1] Outbreaks are associated with rodent extermination when mites seek new hosts. [CDC Travel, p. 301]
FINDINGS
The fever starts 1-2 weeks after the mite bite. The papular rash appears 1-3 days after onset of the fever. Vesicles usually develop on the top of the papules. Rickettsialpox tends to be milder than other rickettsial infections. [ID, p. 1488] The fever lasts about one week and is associated with profuse sweating, headache, myalgia, and photophobia. The rash develops in the first few days of the fever, and it does not affect the palms and soles. Rickettsialpox is not known to be fatal. [Merck Manual, p. 1284] An eschar at the site of the mite bite can be found in more than 90% of cases, and it is associated with regional lymphadenopathy. Transient leukopenia and thrombocytopenia, as well as elevated liver enzymes, may be seen. [PPID, p. 2206] Some patients have nausea/vomiting, abdominal pain, cough, and conjunctivitis. The fever lasts for 6-10 days in untreated patients. [Harrison ID, p. 733]
DIFFERENTIAL DIAGNOSIS:
Rickettsialpox causes a vesicular rash along with a few other infections, e.g., smallpox, varicella, herpes zoster, herpes simplex, Queensland tick typhus, and African tick-bite fever. The last two are similar to Boutonneuse fever. [PPID, p. 2207]
For updated text and symptoms of infectious diseases, see iddx.com.