Pediatric emergency medicine trisk 1832 1832

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