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Ch. 21 - Microbial Diseases of the Skin and Eyes
Tortora - Microbiology: An Introduction 14th Edition
Tortora14th EditionMicrobiology: An IntroductionISBN: 9780138200398Not the one you use?Change textbook
Chapter 21, Problem 3

A 12-year old boy had a fever, rash, headache, sore throat, and cough. He also had a macular rash on his trunk, face, and arms. A throat culture was negative for Streptococcus pyogenes.
The boy most likely had
a. Streptococcal sore throat.
b. Measles.
c. Rubella.
d. Smallpox.
e. Hand-foot-mouth disease.

Verified step by step guidance
1
Step 1: Review the symptoms presented by the boy: fever, rash, headache, sore throat, cough, and a macular rash on the trunk, face, and arms.
Step 2: Note that the throat culture was negative for Streptococcus pyogenes, which helps rule out streptococcal sore throat (option a).
Step 3: Understand the characteristics of each disease option: measles typically presents with fever, cough, coryza, conjunctivitis, and a maculopapular rash starting on the face and spreading downward; rubella also causes a rash but is usually milder and accompanied by lymphadenopathy; smallpox presents with a more pustular rash; hand-foot-mouth disease has vesicular lesions primarily on hands, feet, and mouth.
Step 4: Compare the boy's symptoms and rash distribution with the typical presentation of measles, rubella, smallpox, and hand-foot-mouth disease to identify the most likely diagnosis.
Step 5: Conclude which disease best fits the clinical picture based on the presence of fever, cough, macular rash on face and trunk, and negative streptococcal culture.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Clinical Presentation of Viral Exanthems

Viral exanthems are rashes caused by viral infections, often accompanied by fever and systemic symptoms like headache and sore throat. Recognizing the pattern, distribution, and type of rash (e.g., macular) helps differentiate diseases such as measles, rubella, and others.
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Differential Diagnosis of Febrile Rash Illnesses in Children

Differentiating between illnesses like streptococcal pharyngitis, measles, rubella, smallpox, and hand-foot-mouth disease requires understanding their unique clinical features, incubation periods, and diagnostic tests, such as throat cultures and characteristic rash patterns.
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Role of Throat Culture in Diagnosing Streptococcal Infections

A throat culture is used to detect Streptococcus pyogenes, the bacteria causing streptococcal pharyngitis. A negative culture suggests the sore throat is not bacterial, guiding clinicians to consider viral causes like measles or rubella instead.
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