[Causes and differential diagnosis of flush]

The flush is a transient and recurrent erythema of the upper region of the body, due to a sudden arterial dilatation. First, physicians should confirm the flush and ascertain the location and timing of skin manifestations. The rapid onset and location of the skin rash to the face and anterior chest are the main characteristics of flush. In most of the cases, the flush is emotional, but this should remain a diagnosis of exclusion, as flush may be the presenting manifestation of many systemic or neoplastic disorders. Therefore, a comprehensive diagnostic work-up is necessary, including clinical, biological, and imaging testing. Neoplastic and endocrine causes of flush include VIPoma, carcinoid syndrome, medullary thyroid cancer, mastocytosis, renal cell carcinoma, and pheochromocytoma. Mast cell activation syndrome has been recently described, but it remains a diagnosis of exclusion. This review will first present the different causes of flush, and then will propose a diagnostic algorithm for the physician.