These two lesions are different stages in the same condition. Sweet's syndrome is a curious hypersensitivity syndrome with a massive infiltrate of neutrophils into the dermis giving a pseudoblistering like lesion. The purple, exophytic lesion on the finger looks like Orf, a pox virus infection from sheep or a pyogenic granuloma or even a malignant tumour but it started as a pustule similar to that seen in image one. These pustules can arise at sites of injury such as needle stick injuries from taking blood where the phenomenon is known as pathergy. Patients showing Sweet's syndrome will have a significant leukocytosis in a blood count and sometimes fever and joint swelling. 20% of cases may be associated with a blood or solid organ tumour malignancy and also with inflammatory bowel diseases Crohns and Ulcerative colitis or even rheumatoid arthritis. In many recurrent cases though the cause is not known. Cases respond to oral steroids tapered over 3 weeks. Lesions will heal without scarring which is surprising looking at that finger!
