Differential Diagnosis for Acute Cayenne Pepper-like but Blanchable Rash
- Single most likely diagnosis
- Urticaria: This condition is characterized by itchy, raised hives that can appear anywhere on the body. The rash is often described as having a "cayenne pepper" appearance due to the small, pinpoint nature of the individual lesions. Urticaria is typically blanchable, meaning that the rash will turn white when pressed, which aligns with the description provided.
- Other Likely diagnoses
- Erythema marginatum: This is a type of rash associated with acute rheumatic fever. It presents as a pink ring-shaped lesion that can appear anywhere on the body and is known to be blanchable. While not always described as "cayenne pepper-like," its acute onset and blanchable nature make it a consideration.
- Viral exanthem: Various viral infections can cause rashes that might fit the description given, especially if the rash is composed of small, pinpoint lesions. These rashes are often blanchable and can appear acutely.
- Do Not Miss (ddxs that may not be likely, but would be deadly if missed.)
- Meningococcemia: This is a severe infection caused by Neisseria meningitidis. It can present with a petechial or purpuric rash that might initially appear as small, blanchable spots but quickly becomes non-blanchable as the condition progresses. Early recognition is crucial because meningococcemia can be fatal if not treated promptly.
- Rocky Mountain Spotted Fever (RMSF): This tick-borne illness can cause a rash that starts as small, blanchable spots but later becomes non-blanchable. RMSF is a serious condition that requires immediate medical attention.
- Rare diagnoses
- Schamberg's disease (progressive pigmentary purpuric dermatosis): This is a rare condition characterized by a petechial rash that can appear as small, pinpoint spots. While it's more chronic in nature, early stages might present with a blanchable rash.
- Pigmented purpuric dermatosis (PPD): This group of disorders presents with petechial or purpuric rashes. Some forms might initially have blanchable lesions, although they are generally more chronic than acute.