|
Roseola vs penicillin allergy
When does a rash mean lifelong
trouble?
BY Rupesh Chawla, MD
|
|
Baby C. is a 9-month-old who presents
to your office with his mother several days after his initial illness
-- a runny nose and mild cough associated with 39-40°C fevers
every day. Over the weekend, they had been to a walk-in clinic, where
the doctor had prescribed amoxicillin for an upper respiratory tract
infection (URI). Now, the fever has disappeared but he has a rash
all over his body. It doesn't appear to bother him, but can it be
a reaction to the antibiotic? Does this child have a penicillin allergy,
for which he'll always have to be careful?
Presentation
Physical examination
- no acute distress, seems well
- vital signs: temperature 36.9°C,
heart rate 120 b.p.m., respiratory rate 22, blood pressure
normal
- throat: mildly red
- neck: shotty cervical lymphadenopathy
with prominent non-tender, posterior occipital nodes
- fine red maculopapular rash over
the chest, abdomen and extremities
Investigations
Diagnosis
In an infant this age, the presentation
is classic for roseola. He should never have been started
on antibiotics and they can be stopped, but most importantly,
this boy should not be labelled as penicillin-allergic.
|
Making the case
Roseola
Roseola is the most common clinical manifestation of human herpesvirus
6 (HHV-6). Worldwide, it affects boys and girls equally and has
no seasonal predilections. Primary infection occurs at ages 6 months
to 3 years and is a major cause of fevers in 6-18-month-olds. It's
responsible for 20% of visits to emergency departments for acute
illness in babies 6-12 months.
Clinical manifestations
- very similar to other non-specific febrile illnesses, making
differentiation difficult
- incubation period 9-10 days
- high-grade fever, average 39-40°C, abrupt in onset, lasting
3-5 days
- often no localizing signs of illness
- 50% have a URI and nasal congestion
- diffuse pharyngeal erythema, mild maculopapular exanthem on
soft palate/uvula, possibly inflamed tympanic membranes
- eyelids may appear puffy
- diarrhea and vomiting in 1/3 of cases
- classic maculopapular rash -- appears after fever breaks, occasionally
sooner
- mild cervical nodes can be present on initial evaluation, but
distinctive ones in posterior occipital region appear after 3-4
days
- central nervous system involvement -- bulging anterior fontanelle
in ¼ of cases, febrile seizures, rare reports of encephalopathy
and encephalitis
The course of illness is 3-7 days. Usually, infants recover rapidly
and completely without treatment. When the rash comes out, the child
is no longer contagious.
Penicillin allergy
According to Ibia et al, rashes occur in 7.3% of children given
oral antibiotics commonly used in primary care. Beta-lactams account
for the majority of cases, with penicillin and sulfonamides the
most frequent causes. Although most reactions are minor and transient,
the complexity is in determining which may ultimately lead to severe
reactions that require inpatient care and can even be fatal.
Antibiotic allergies also affect patient/family compliance and
therapeutic outcomes. They lead to a cycle of prescribing alternative
agents that are often more expensive and broad-spectrum, leading
to the emergence of antibiotic-resistant strains.
There are two types of reactions:
Immediate
- occur within first hour of exposure
- mediated by IgE specific antibodies -- type I hypersensitivity
- release of histamine and other vasoactive mediators
- urticaria and/or angioedema, rhinitis, bronchospasm, anaphylactic
shock
|
