Differential Diagnosis for Pruritic Rash with Fever

Single Most Likely Diagnosis

• Viral Exanthem: This is the most common cause of a pruritic rash with fever, especially in children. Viral exanthems, such as those caused by enteroviruses, adenoviruses, and parvovirus B19, often present with a rash and fever, and can be pruritic.

Other Likely Diagnoses

• Allergic Contact Dermatitis: This condition occurs when the skin comes into contact with an allergen, leading to a pruritic rash. Fever can be present if the reaction is severe or if there is a secondary infection.
• Atopic Dermatitis (Eczema): Eczema is a chronic condition characterized by itchy, inflamed skin. It can flare up with fever, especially if there is a secondary bacterial infection.
• Insect Bite Reactions: Reactions to insect bites can cause pruritic rashes and may be accompanied by fever, especially if there is an allergic reaction or secondary infection.
• Drug Rash: Certain medications can cause a pruritic rash, which may be accompanied by fever. This is often seen with antibiotics, anticonvulsants, and NSAIDs.

Do Not Miss Diagnoses

• Meningococcemia: This is a life-threatening condition caused by Neisseria meningitidis. It can present with a petechial or purpuric rash, fever, and may be pruritic in some cases. Early recognition and treatment are crucial.
• Rocky Mountain Spotted Fever (RMSF): RMSF is a tick-borne illness that can cause a pruritic rash, fever, and headache. It is essential to consider this diagnosis in patients with a history of tick exposure.
• Stevens-Johnson Syndrome/Toxic Epidermal Necrolysis (SJS/TEN): These are severe skin conditions usually triggered by medications or infections. They can present with a pruritic rash, fever, and mucous membrane involvement, and are medical emergencies.

Rare Diagnoses

• Erythema Multiforme: A skin condition characterized by target lesions, which can be pruritic and are often accompanied by fever. It can be triggered by infections or medications.
• Pityriasis Rosea: A condition that causes a pruritic rash, often with a "herald patch" followed by a secondary eruption. Fever can be present, especially at the onset.
• Kawasaki Disease: A rare condition in children that can cause a pruritic rash, fever, and other systemic symptoms. It is essential to consider this diagnosis in children with unexplained fever and rash.