Differential Diagnosis for Purpuric Rash with High IgE, ANA Positive, and Eosinophilia

Single Most Likely Diagnosis

• Churg-Strauss Syndrome (Eosinophilic Granulomatosis with Polyangiitis, EGPA): This condition is characterized by asthma, eosinophilia, and vasculitis, which can present with purpuric rash, high IgE levels, and positive ANA. The combination of these symptoms makes EGPA a strong candidate for the single most likely diagnosis.

Other Likely Diagnoses

• Hyper-IgE Syndrome (Job Syndrome): Although primarily known for its recurrent cutaneous and pulmonary infections, some forms of hyper-IgE syndrome can present with vasculitic rashes and elevated eosinophils, making it a plausible diagnosis.
• Systemic Lupus Erythematosus (SLE): SLE can present with a wide range of symptoms, including purpuric rashes, high IgE levels, and eosinophilia, especially in the context of a positive ANA. However, the presence of high IgE and eosinophilia is less common in SLE.
• Urticarial Vasculitis: This condition involves inflammation of the blood vessels and can present with urticarial lesions that may resemble purpura, elevated IgE, and eosinophilia. A positive ANA can also be seen in some cases.

Do Not Miss Diagnoses

• Wegener's Granulomatosis (Granulomatosis with Polyangiitis, GPA): Although GPA typically presents with a different set of symptoms (e.g., respiratory and renal involvement), it can occasionally manifest with purpuric rashes and eosinophilia. Missing this diagnosis could be catastrophic due to its potential for severe organ damage.
• Polyarteritis Nodosa (PAN): PAN is a vasculitis that can affect various organs and sometimes presents with skin manifestations, including purpura. While eosinophilia and high IgE are not typical, PAN is a diagnosis that should not be missed due to its potential severity.

Rare Diagnoses

• Eosinophilic Granuloma with Polyangiitis (EGPA) Variants: There are rare variants of EGPA that might present differently but still could fit the given symptoms.
• Allergic Granulomatosis: A rare condition that could potentially present with similar symptoms, though it's less well-defined and might overlap significantly with EGPA.
• Malignancy-Associated Vasculitis: Certain malignancies can cause vasculitis, which might present with purpuric rashes, eosinophilia, and elevated IgE levels. This would be a rare but critical diagnosis to consider.