A bona fide association between Sweet's syndrome probably exists with the following conditions: cancer (including both hematologic malignancies and solid tumors) (Figure 8), infections (predominantly of the upper respiratory tract and the gastrointestinal tract), inflammatory bowel disease (including both Crohn's disease and ulcerative colitis), medications (granulocyte-colony stimulating factor is the most commonly reported drug) and pregnancy (Table 5). This evidence concerns the gene CSF3 and sweet syndrome.