Differential Diagnosis for Fever, Body Malaise, and Pruritic Rashes

Single Most Likely Diagnosis

• Viral Exanthem: This is a common condition characterized by fever and rash, often seen in children but can occur in adults. The pruritic nature of the rash could be due to the body's immune response to the virus. Viral exanthems are typically self-limiting and caused by a variety of viruses.

Other Likely Diagnoses

• Allergic Reaction: An allergic reaction to a drug, food, or environmental factor could present with fever, malaise, and a pruritic rash. The timing and onset of symptoms in relation to exposure to potential allergens would be crucial in diagnosing this condition.
• Insect Bite Reaction: Reactions to insect bites can cause pruritic rashes and, in some cases, systemic symptoms like fever and malaise, especially if there is an allergic component to the reaction.
• Eczema/Dermatitis: Conditions like atopic dermatitis or contact dermatitis can present with pruritic rashes. While they might not typically cause systemic symptoms like fever, in severe cases or with secondary infection, such symptoms could occur.

Do Not Miss Diagnoses

• Meningitis: Although meningitis typically presents with symptoms like headache, stiff neck, and fever, in some cases, especially in the early stages, it might present with rash (e.g., meningococcal meningitis). The rash associated with meningococcal meningitis is usually petechial or purpuric but can be pruritic in the initial stages.
• Septicemia: Bacterial septicemia can cause a wide range of symptoms including fever, malaise, and rash. The rash can be pruritic and is a sign of a potentially life-threatening condition.
• Lymphoma: Certain types of lymphoma, like cutaneous T-cell lymphoma, can present with skin manifestations including pruritic rashes, along with systemic symptoms like fever and malaise.

Rare Diagnoses

• Pityriasis Rosea: A condition characterized by a rash that is often preceded by a viral-like illness with fever and malaise. The rash is typically pruritic.
• Syphilis: Secondary syphilis can present with a wide range of symptoms including fever, malaise, and a rash that can be pruritic. This diagnosis is less common but should be considered, especially in sexually active individuals.
• Parvovirus B19: In adults, parvovirus B19 infection can cause a pruritic rash along with fever and malaise, though this is less common than in children.