What is the likely diagnosis and recommended management for an 8‑year‑old girl with a one‑day fine flesh‑colored papular rash on the face and erythematous papular rash on the chest and neck, mild sore throat, no fever, and non‑pruritic rash?

Likely Diagnosis and Management

This presentation is most consistent with scarlet fever (streptococcal pharyngitis with exanthem), and you should perform a rapid strep test and throat culture immediately, then initiate penicillin or amoxicillin without waiting for culture results if the rapid test is positive. 1

Clinical Reasoning

The combination of mild sore throat, fine flesh-colored papular rash on the face, and erythematous papular rash on chest/neck in an 8-year-old girl strongly suggests scarlet fever (Group A streptococcal pharyngitis with exanthem). 1 The key distinguishing features here are:

• Age group: 5-15 years is the peak age for streptococcal pharyngitis 1
• Rash distribution: Scarlet fever typically involves trunk and extremities while sparing palms and soles (unlike RMSF) 2, 3
• Absence of fever: While fever is common in scarlet fever, its absence does not exclude the diagnosis 1
• Non-pruritic rash: Consistent with scarlet fever rather than viral exanthems or drug reactions 4

Critical Life-Threatening Differentials to Exclude

Before settling on scarlet fever, you must actively exclude Rocky Mountain Spotted Fever (RMSF), which can be fatal within 9 days if untreated. 5, 3

Red Flags for RMSF (all absent in this case):

• Fever, headache, severe myalgias: Not present 5, 3
• Rash on palms/soles: Not described 5, 2, 3
• Thrombocytopenia: Would need CBC to assess 1, 3
• Recent outdoor activities/tick exposure: Should be queried 1, 5
• Summer season (April-September): Increases RMSF suspicion 5

Important caveat: Up to 40% of RMSF patients report no tick bite history, and up to 20% never develop a rash, so absence of these features does not completely exclude RMSF. 5, 3 However, the absence of fever makes RMSF highly unlikely in this case. 5, 3

Immediate Diagnostic Workup

Essential Tests (perform immediately):

• Rapid streptococcal pharyngitis screen: Gold standard for point-of-care diagnosis 1
• Throat culture: If rapid test is negative, culture should still be sent 1
• Complete blood count with differential: To assess for thrombocytopenia (would suggest RMSF) or leukopenia (would suggest viral infection) 1, 3

Additional History to Obtain:

• Outdoor activities, camping, hiking, or tick exposure in the past 2 weeks 1, 5
• Geographic location and season 5, 3
• Medication history (to exclude drug reaction) 1, 4
• Sick contacts or similar illness in family members 3
• Pet exposure (dogs can be sentinels for RMSF) 3

Physical Examination Priorities:

• Check palms and soles carefully for rash (presence would shift diagnosis toward RMSF) 5, 2, 3
• Examine scalp, axillae, groin, waist, and under socks/beltline for attached ticks 1
• Assess for petechiae (would suggest RMSF or meningococcemia) 1, 3
• Look for tonsillopharyngeal erythema, exudates, and tender anterior cervical lymphadenopathy (supports streptococcal pharyngitis) 1

Treatment Algorithm

If Rapid Strep Test is Positive:

• Initiate oral penicillin V or amoxicillin immediately for 10 days 2
• Treatment should not be delayed for culture results because untreated streptococcal infection can lead to acute rheumatic fever, post-streptococcal glomerulonephritis, and suppurative complications 2

If ANY Suspicion for RMSF Exists:

• Start doxycycline immediately without waiting for laboratory confirmation 5, 2, 3
• Age is not a contraindication for doxycycline in suspected RMSF 2
• Consider intramuscular ceftriaxone to cover meningococcemia pending blood cultures 5

If Clinical Picture Remains Unclear:

• Obtain CBC, comprehensive metabolic panel, and blood cultures 1, 3
• If thrombocytopenia, hyponatremia, or elevated hepatic transaminases are present, start doxycycline empirically for presumed RMSF 3

Other Differential Diagnoses (Less Likely)

Viral Exanthems:

• Enteroviral infections: Most common cause of maculopapular rashes in children, but typically involve trunk and extremities while sparing face 3, 6
• Roseola (HHV-6): Rash appears after fever resolution, not during active illness 5, 3
• Epstein-Barr virus: More likely if patient received ampicillin/amoxicillin 3

Drug Reaction:

• Less likely given no medication history mentioned, but should be queried 4
• Drug eruptions typically present as fine reticular maculopapular rashes 3

Critical Pitfalls to Avoid

• Never exclude RMSF based solely on absence of tick bite history (40% have no recalled exposure) 5, 3
• Never exclude RMSF based on absence of fever in the first 1-2 days of illness 5
• Never wait for serologic confirmation before starting doxycycline if RMSF is suspected (serology is negative in the first week) 5, 3
• Never dismiss mild sore throat as "just viral" without performing strep testing in this age group 1

Follow-Up and Reassessment

• Reevaluate within 24-48 hours to confirm clinical improvement after initiating antibiotics 2
• If no improvement or worsening despite appropriate antibiotics, broaden differential diagnosis and consider complications 2
• Educate caregivers about warning signs requiring urgent return: increasing fever, lethargy, breathing difficulty, rash progression to palms/soles, or development of petechiae 2