Differential Diagnosis for Coalescing Rash on Extremities with Fever
Single Most Likely Diagnosis
- Viral Exanthem (e.g., measles, rubella, roseola): This is a common cause of a coalescing rash with fever in children and young adults. The rash often starts on the face or trunk and spreads to the extremities.
Other Likely Diagnoses
- Bacterial Infections (e.g., streptococcal or staphylococcal infections): These can cause a coalescing rash, especially if there is an underlying skin infection such as impetigo or cellulitis.
- Allergic Reactions (e.g., allergic contact dermatitis): Certain allergens can cause a coalescing rash, especially if the individual has been exposed to a new substance.
- Kawasaki Disease: An acute febrile illness that primarily affects children, characterized by a coalescing rash, fever, and other systemic symptoms.
Do Not Miss Diagnoses
- Meningococcemia: A life-threatening infection caused by Neisseria meningitidis, which can present with a coalescing rash (purpura) and fever. Prompt recognition and treatment are crucial.
- Rocky Mountain Spotted Fever (RMSF): A tick-borne illness caused by Rickettsia rickettsii, characterized by a coalescing rash and fever. Delayed treatment can lead to severe complications.
- Toxic Shock Syndrome: A medical emergency caused by bacterial toxins, often presenting with a coalescing rash, fever, and hypotension.
Rare Diagnoses
- Erythema Multiforme: A skin condition characterized by target lesions, which can coalesce and be accompanied by fever. It is often triggered by infections or medications.
- Secondary Syphilis: A systemic infection caused by Treponema pallidum, which can present with a coalescing rash and fever, among other symptoms.
- Leptospirosis: A zoonotic infection caused by Leptospira bacteria, which can cause a coalescing rash, fever, and other systemic symptoms.