Rickettsialpox Differential Diagnoses

Updated: Jun 03, 2020
  • Author: Darvin Scott Smith, MD, MSc, DTM&H; Chief Editor: John L Brusch, MD, FACP  more...
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Diagnostic Considerations

Human spotted fever secondary to Rickettsia parkeri infection

African tick bite fever secondary to Rickettsia africae infection

Mediterranean Spotted Fever

Scrub Typhus [18, 19]



Table 1. Characteristics of Similar Conditions (Open Table in a new window)



Generalized Rash

Clinical Features


Rickettsialpox secondary to R akari infection

A red papule with a vesicle in the center dries and forms a black eschar with surrounding induration. Multiple eschars are possible.

The papulovesicular rash is usually on the trunk and extremities; the palms, soles, and oral mucosa may also be involved.

The papule precedes the febrile illness and mild systemic symptoms. Regional lymphadenopathy may develop.

See Frequency

Chickenpox secondary to varicella zoster infection

The papule turns into a vesicle on an erythematous base and resembles a "dew drop on a rose petal."

The rash begins on the head and progresses to the trunk, arms, and then legs; vesicles are present in all stages.

It is common in children. No black eschar is present.


Mediterranean spotted fever secondary to Rickettsia conorii infection

At the site of a tick bite, a single eschar with a red halo forms.

The rash is generalized, involves the palms and soles, and is often maculopapular, occasionally petechial.

Fever, headache, myalgias may develop. The onset is abrupt. The disease may be severe in context of comorbidity.

North Africa, Middle East, Southern Europe

African tick bite fever secondary to R africae infection

Single or multiple eschars with regional lymphadenopathy

A scant generalized rash, vesicular or maculopapular, may be present. Conversely, the rash may be absent.

Fever, headache, myalgias, regional lymphadenopathy; associated with reports of subacute neuropathy

Sub-Saharan Africa, Caribbean

Human spotted fever secondary to R parkeri infection

Single or multiple eschars develop from erythematous papules.

Scant nonpruritic papules

Fever, headache, myalgias, arthralgias

United States

Scrub typhus secondary to Orientia tsutsugamushi infection

A vesicle or black scab appears on an erythematous base at the bite site.

Vesicles are usually on the trunk or extremities.

The rash fades within a few days; pneumonitis is common.

Asia-Pacific rim

Differential Diagnoses