Differential Diagnosis for Diffuse Macular Rash
Single Most Likely Diagnosis
- Viral exanthem: This is a common cause of diffuse macular rash in both children and adults, often associated with viral infections such as coxsackievirus, echovirus, or adenovirus. The rash is typically not itchy and can appear anywhere on the body except the palms and soles.
Other Likely Diagnoses
- Drug eruption: Many medications can cause a diffuse macular rash as a side effect. This type of rash can occur at any time after starting a new medication and is not necessarily itchy.
- Allergic reaction: An allergic reaction to a substance can cause a macular rash. While these are often itchy, there are instances where they may not be.
- Secondary syphilis: This condition can cause a diffuse macular rash that typically does not itch and can appear on the trunk and limbs but spares the palms and soles.
Do Not Miss Diagnoses
- Meningococcemia: Although rare, this condition is life-threatening and can present with a diffuse macular rash that progresses to petechiae or purpura. It's crucial to consider this diagnosis, especially if the patient has fever, headache, or other signs of severe illness.
- Toxic shock syndrome: This is a medical emergency that can cause a diffuse macular rash, fever, and other systemic symptoms. It's often associated with bacterial infections, particularly Staphylococcus aureus or Streptococcus pyogenes.
- Septicemia: Bacterial septicemia can cause a rash among other symptoms. Early recognition and treatment are critical.
Rare Diagnoses
- Kawasaki disease: An acute febrile illness of childhood characterized by a diffuse macular rash, among other criteria. It's rare but important to consider due to its potential for cardiac complications.
- Erythema infectiosum (Fifth disease): Caused by parvovirus B19, this condition typically presents with a "slapped cheek" appearance but can also cause a diffuse macular rash on the body.
- Scarlet fever: Although the rash in scarlet fever is typically described as sandpapery and accompanied by other symptoms like a sore throat, it can sometimes appear as a diffuse macular rash.