Petechial/Purpuric Rashes- THE ALGORITHMIC APPROACH These rashes can be especially challenging and are associated with devastating differential diagnoses; however, an algorithmic approach can help the physician narrow the diagnosis with confidence (Figure 4, page 12). Additionally, remembering the etiology of palpable versus nonpalpable lesions is paramount. Palpable (raised) purpura occurs in vasculitic diseases secondary to inflammation or infection. Nonpalpable purpura presents in thrombocytopenic conditions (flat, subcutaneous hemorrhages). Patients with petechiae/purpura with fever or toxicity require emergent evaluation. If the lesions are palpable, the differential diagnosis includes meningococcemia, disseminated gonococcal disease, endocarditis, RMSF, and Henoch-Schönlein purpura. Those with petechiae/purpura with fever/toxicity but with nonpalpable lesions may have purpura fulminans, disseminated intravascular coagulopathy (DIC), or TTP. If the patient is afebrile with a petechial or purpuric rash, the diagnosis may be far simpler and less ominous. Nontoxic patients with palpable lesions may have a vasculitis, such as autoimmune vasculitis; those with nonpalpable lesions may have idiopathic thrombocytopenic purpura. While all patients with petechiae require complete assessment, those with nonpalpable petechiae are more likely to have thrombocytopenia. #Diagnosis #Dermatology #Petechial #Petechiae #Purpural #Purpuric #Rash #Algorithm #Nonpalpable #Differential
