Sweet's Syndrome and Pathergy

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!

Sweet's Syndrome

Another in the series of not quite what it looks. These lesions arose on the backs of both hands as possible blisters that then crusted although the one on the little finger remained as a purplish nodule. The patient had multiple myeloma. Infection was considered the likeliest cause by his treating doctors but swabs were negative and high dose antibiotics made no difference. The alleged blisters did not break and leak any fluid so were not true blisters. Patients who have myeloma and other myeloproliferative leukaemic disorders are certainly susceptible to infections but they also get a rare skin rash called Sweet’s syndrome after the UK dermatologist who first described the disorder. It is a neutrophilic condition where masses of neutrophils invade the dermis and cause subepidermal oedema simulating a blister. Pustules can sometimes be seen in the overlying epidermis but are inflammatory not infective. Sweets responds to high dose oral steroids reducing over three weeks. The condition also commonly occurs in people with inflammatory bowel disorders such as Crohns and Ulcerative colitis.