Differential Diagnosis for Maculopapular Rash Eruption
Single Most Likely Diagnosis
- Pityriasis Rosea: This condition is characterized by a maculopapular rash that starts with a single, large, pink or purple patch (herald patch), followed by the development of smaller, similar patches. The rash is often itchy and can be widespread. The description of large hexagonal pink/purple patches fits well with the clinical presentation of pityriasis rosea.
Other Likely Diagnoses
- Urticaria: Although urticaria typically presents with wheals, some cases can have a maculopapular appearance. The itchiness and potential for widespread distribution align with the symptoms described.
- Atopic Dermatitis (Eczema): This chronic condition can cause itchy, maculopapular rashes that can be widespread. While the hexagonal shape is not typical, the variability in presentation could occasionally fit this description.
- Drug Eruption: Many medications can cause maculopapular rashes as a side effect. These rashes can be itchy and widespread, although the specific pattern of hexagonal patches might be less common.
Do Not Miss Diagnoses
- Syphilis (Secondary): This condition can cause a wide range of skin manifestations, including maculopapular rashes. Although less common, syphilis can present with unusual patterns, and missing this diagnosis could have significant consequences.
- Lyme Disease: In its early stages, Lyme disease can cause a distinctive rash known as erythema migrans, which can sometimes appear as a maculopapular rash. While the classic "bull's-eye" pattern is more typical, atypical presentations can occur.
- Meningococcemia: This severe infection can cause a petechial or purpuric rash, which might initially appear maculopapular. The potential for rapid progression to a life-threatening condition makes this a critical diagnosis not to miss.
Rare Diagnoses
- Kawasaki Disease: Although primarily known for affecting children, Kawasaki disease can cause a maculopapular rash among other symptoms. The rash is typically accompanied by fever, conjunctivitis, and changes to the lips and oral cavity.
- Erythema Multiforme: This condition can present with target lesions but sometimes appears as a maculopapular rash. It's often associated with infections or medication use.
- Parvovirus B19 (Fifth Disease): Characterized by a "slapped cheek" appearance, parvovirus B19 can also cause a maculopapular rash on the body. The rash is usually not itchy but can be widespread.