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Kawasaki Disease (see Chapter 101 Rheumatologic Emergencies )
Kawasaki disease can present with a wide variety of rashes, including
morbilliform and urticarial. Conjunctivitis, when present, is unique in that it is
nonexudative with limbal sparing. Other dermatologic manifestations include red
cracked lips, strawberry tongue, and erythematous oropharynx, and erythema,
swelling, and/or induration of peripheral extremities.
The most commonly associated rash is a generalized exanthem with raised
erythematous plaques; however, the rash may also present with an erythematous
maculopapular, morbilliform, scarlatiniform, or erythema marginatum–like
pattern. Peeling in the diaper/groin area is also frequently observed early. The
exanthem may be fleeting or persist for 2 to 3 days. During the later stages of the
acute phase, periungual desquamation and peeling of the palms, soles, or perineal
area develop.
Measles (Rubeola)
Measles was one of the most common viral exanthems before the measles
vaccine. It is now on the rise again because of increased opting out of
vaccinations for children. The incubation period is 10 to 14 days after direct
contact with droplets from an infected person. In its classic form, measles has a
highly characteristic natural history. Two to 3 days after the onset of the
prodromal symptoms of cough, coryza, conjunctivitis, and fever, Koplik spots
occur in the mouth, followed 12 to 24 hours later by the cutaneous exanthem.
Most typically, Koplik spots appear as pinpoint white lesions on a red base on the
buccal mucosa adjacent to the molars; however, they may be seen on any of the
mucosal surfaces of the oral cavity except the tongue.
The measles exanthem begins on the head as reddish maculopapules and
spreads caudally during the next 4 to 5 days. Within 1 to 2 days of its appearance,
the discrete maculopapular lesions coalesce to produce the confluent phase of the
rash. Hence, within 2 to 3 days of onset, the rash on the face becomes confluent,
whereas the rash on the lower extremities still consists of individual
maculopapules. Modified measles occurs in children who have received serum
immunoglobulin after exposure to measles. Measles may still occur, but the

incubation period may be delayed up to 21 days. The symptoms, although
following the usual progression, will be milder. A faint rash and mild febrile
illness may occur 7 to 10 days after immunization with the live attenuated
measles vaccine.
Rocky Mountain Spotted Fever


RMSF is caused by Rickettsia rickettsii transmitted by the bite of a tick (see
Chapter 66 Rash: Bacterial and Fungal Infections/Rash: Maculopapular ).
Although initially confined to the Rocky Mountain States (hence, its name),
confirmed cases have been reported from all parts of the United States with
varying tick vectors. The primary determinants in patient outcome are early
diagnosis and treatment. The best outcomes are associated with the initiation of
doxycycline therapy by day five of illness.
The rash of RMSF begins on the third or fourth day of a febrile illness as a
morbilliform eruption on the extremities, most commonly the wrists and ankles.
Over the next 2 days, the rash becomes generalized by spreading centrally to
involve the back, chest, and abdomen. Initially, the rash consists of erythematous
macules that blanch on pressure; they then become more confluent and purpuric.
Notably, the hemorrhagic lesions predominate in the peripheral distribution,
involving the palms of the hands and the soles of the feet. The severity of the rash
is proportional to the severity of the disease.
All patients with RMSF have some degree of vasculitis that is the basis for
many of the associated systemic symptoms. An overall toxic appearance is
common. Systemic signs and symptoms include fever, headache, myalgia,
conjunctivitis, vomiting, seizures, myocarditis, heart failure, shock; periorbital,
facial, or peripheral edema; and disseminated intravascular coagulation or
purpura fulminans.
Diagnosis is best made by polymerase chain reaction (PCR) testing.
Thrombocytopenia, hyponatremia, and increased aminotransferases usually

develop as the disease process progresses.
Doxycycline is the drug of choice for therapy in patients of all ages at a dose of
4 mg/kg/day in two divided doses (maximum of 100 mg two times a day),
intravenously or orally.
Ehrlichiosis
Ehrlichiosis is most common during the warmer months when ticks are most
prevalent. Nomenclature has undergone multiple changes. Currently, disease in
the United States is due to three distinct obligate intracellular bacteria: Ehrlichia
chaffeensis (human monocytic ehrlichiosis or HME), Anaplasma
phagocytophilum agent (human granulocytic anaplasmosis or HGA), or Ehrlichia
ewingii (E. ewingii ehrlichiosis). Infections with any of these bacteria cause an
illness very similar to RMSF. Rash is a less consistent feature of ehrlichiosis but
when present may be macular, morbilliform, or petechial and is more commonly
seen in pediatric patients infected with E. chaffeensis. Unlike RMSF, rash may


occur anywhere on the body and is less commonly seen on the palms and/or
soles. Vasculitis is less prominent, and leukopenia, anemia, and hepatitis are more
common in ehrlichiosis than in RMSF.
As for RMSF, doxycycline is the drug of choice for therapy in patients of all
ages and at the same dose of 4 mg/kg/day in divided doses (maximum 100 mg
twice a day). Therapy is continued until the patient is afebrile for at least 2 to 3
days and for a minimum total course of 5 to 10 days. Clinical improvement is
usually apparent within 3 days, and if not, an alternative diagnosis should be
sought. Disease may be more severe or even fatal in untreated patients. Early
initiation of therapy minimizes morbidity and mortality.
Dengue Fever
Dengue fever is caused by four dengue viruses transmitted by Aedes mosquitos
and is seen in tropical and subtropical areas of almost all continents (including
areas of Puerto Rico and the Caribbean basin and now in Florida). Many cases are

asymptomatic. In symptomatic cases, initial constitutional symptoms include
sudden onset of high fever, severe headache, myalgia, arthralgia, and abdominal
pain. During the course of fever that lasts 2 to 7 days, back and leg pain may be
severe, hence, the disease’s nickname “break bone fever.” The development of a
hemorrhagic vasculitis, most common in patients younger than 15 years, leads to
the more concerning subtype called dengue hemorrhagic fever. The term dengue
shock syndrome is used in even more severe cases when increased vascular
permeability leads to shock. Encephalopathy, hepatitis, myocardiopathy, intestinal
bleeding, and pneumonia are other complications.
Two distinct rashes may be seen, which coincide with the disease’s biphasic
fever pattern. The first rash is a generalized, transient, macular rash that blanches
under pressure and is seen within the first 24 to 48 hours of the onset of systemic
symptoms. The second rash coincides with or occurs 1 to 2 days after
defervescence and is generalized morbilliform, sparing the palms and soles.
Diagnosis is based on clinical suspicion and potential exposure based on the
virus’s geographic distribution. Serologic testing is available as is viral isolation
and measurement of serum immunoglobulin antibodies in paired serum
specimens obtained 4 weeks apart. Treatment is supportive, and may require
aggressive fluid management and pain control. Intravenous immunoglobulin
and/or plasma exchange may be of benefit in severe cases.

Causes of Other Widespread Rashes Associated With Fever
Non–life-threatening illnesses associated with fever and widespread rash include
coxsackievirus infections, erythema infectiosum, scarlet fever, and early varicella.


Harder to diagnose are rashes associated with Epstein–Barr virus, Mycoplasma
infections, roseola infantum, disseminated gonorrhea, and secondary syphilis.
Erythema Infectiosum (Fifth Disease)
Erythema infectiosum is a benign disease caused by parvovirus B19, the same

virus that can cause aplastic crises in patients with sickle cell anemia. For the
immunocompetent, nongravid host, fifth disease is usually of no consequence,
with the only systemic symptom being fever in 15% to 30% of cases. On the face
is a characteristic, intensely erythematous, “slapped cheek” rash, often with
relative circumoral pallor ( Fig. 88.15A ). In addition, a symmetric red lace-like
rash is seen on the arms and then trunk, buttocks, and thighs, which may be
pruritic ( Fig. 88.15B ). In its acute phase, the rash usually lasts only for a few
days but can wax and wane in intensity with environmental changes (e.g.,
exposure to heat or sunlight) for weeks and sometimes months. In a small subset
of patients, parvovirus B19 causes the atypical papular purpuric gloves and socks
syndrome (PPGSS) with a typically painful purpuric exanthem limited to the
hands and feet. Immunocompromised children or those with hemolytic anemias
can develop red cell aplasia and symptoms associated with a chronic anemia.
Diagnosis is usually made on a clinical basis alone but may be confirmed in an
immunocompetent host by measuring parvovirus B19–specific IgM antibody.
PCR is the best modality for diagnosis in an immunocompromised host. No
specific therapy is necessary in immunocompetent hosts. For a chronic infection
in an immunodeficient patient, IVIG therapy should be considered. Because
parvovirus is associated with fetal anemia, congestive heart failure, and hydrops,
exposed pregnant women should be referred to their physicians to discuss
possible parvovirus antibody testing.
Scarlet Fever
Scarlet fever is caused by phage-infected Group A Streptococcus that makes an
erythrogenic toxin. This disease does not appear to be any more serious than
Group A streptococcal infection without rash. Scarlet fever is most commonly
associated with streptococcal pharyngitis but may occur in association with
pyoderma or an infected wound.
The diagnosis of scarlet fever can be made clinically in a child with signs and
symptoms of pharyngitis who has a fine, raised, generalized morbilliform rash.
The skin has a coarse or sandpapery feel on palpation. Typically, there is sparing

of the circumoral area, leading to circumoral pallor. There is usually a bright
erythema of the tongue and hypertrophy of the papillae, leading to the term