Introduction:

Rashes are common manifestations in patients presenting with acute febrile illness (AFI), offering important diagnostic clues to the underlying etiology. This article explores the various rashes associated with AFI, their characteristic patterns, and differential diagnoses.

Viral Exanthems:

Measles (Rubeola):

• Characteristics: Morbilliform rash starting on the face and spreading downwards, accompanied by cough, coryza, and conjunctivitis.
• Differential Diagnosis: Rubella, enterovirus infections.

Rubella (German Measles):

• Characteristics: Fine, pink maculopapular rash starting on the face and spreading to the trunk and extremities, with posterior cervical lymphadenopathy.
• Differential Diagnosis: Measles, parvovirus B19 infection.

Dengue Fever:

• Characteristics: Petechial or maculopapular rash occurring in the context of fever, myalgia, headache, and retro-orbital pain.
• Differential Diagnosis: Other arboviral infections, such as chikungunya or Zika virus.

Bacterial Infections:

Scarlet Fever (Group A Streptococcal Infection):

• Characteristics: Fine, sandpaper-like rash appearing on the trunk and spreading to the extremities, associated with sore throat, fever, and strawberry tongue.
• Differential Diagnosis: Viral exanthems, Kawasaki disease.

Rocky Mountain Spotted Fever (Rickettsia rickettsii):

• Characteristics: Maculopapular rash starting on the wrists and ankles and spreading centrally, often with associated fever, headache, and myalgia.
• Differential Diagnosis: Other rickettsial infections, leptospirosis.

Systemic Inflammatory Conditions:

Kawasaki Disease:

• Characteristics: Erythematous rash, often morbilliform or erythema multiforme-like, along with fever, conjunctival injection, mucosal changes, and extremity changes (e.g., desquamation).
• Differential Diagnosis: Scarlet fever, toxic shock syndrome.

Acute Rheumatic Fever:

• Characteristics: Erythema marginatum, a non-pruritic, serpiginous rash, may occur along with fever, migratory polyarthritis, carditis, and chorea.
• Differential Diagnosis: Scarlet fever, viral exanthems.

Infectious Diseases:

Zika Virus Infection:

• Characteristics: Maculopapular rash involving the face, trunk, and extremities, accompanied by fever, joint pain, conjunctivitis, and headache.
• Differential Diagnosis: Dengue fever, chikungunya.

Parvovirus B19 Infection:

• Characteristics: "Slapped cheek" appearance followed by a lacy, reticular rash on the trunk and extremities, often in the context of fever, arthralgia, and malaise.
• Differential Diagnosis: Rubella, erythema infectiosum.

Drug Reactions:

Drug Rash with Eosinophilia and Systemic Symptoms (DRESS):

• Characteristics: Morbilliform rash with associated fever, eosinophilia, lymphadenopathy, and organ involvement (e.g., liver, kidney).
• Differential Diagnosis: Stevens-Johnson syndrome/toxic epidermal necrolysis, viral exanthems.

Conclusion:

Rashes associated with acute febrile illness encompass a diverse spectrum of patterns and etiologies, ranging from viral exanthems to bacterial infections and systemic inflammatory conditions. Recognizing the characteristic features of each rash aids in narrowing down the differential diagnosis and facilitating appropriate management strategies.

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