1. A diagnosis of Sweet’s syndrome is made by taking your medical history to see if you have had any infections, other health conditions, are pregnant, or are taking any medications that could cause it.
2. Your temperature will be taken. Sweet’s syndrome normally causes an unexplained fever of 38 degrees Centigrade (100.4 degrees Fahrenheit) or above. Sometimes a fever is not present, and is slightly less likely to occur in those who develop Sweet’s syndrome secondary to cancer or certain blood disorders (15-20% of cases).
3. Blood tests will be needed to detect any inflammation or infection in the body, and some additional blood tests might be needed to rule out cancer or other conditions as a cause for Sweet’s syndrome.
4. Most people with Sweet’s syndrome have skin lesions (skin rash). Your dermatologist will need to take a biopsy (tissue sample) of a lesion for detailed microscopic examination to confirm diagnosis and rule out any other conditions that might be confused with Sweet’s syndrome. On rare occasions, skin lesions are not present.
Main diagnostic criteria (Oakley, 2015).
- Abrupt onset of tender or painful red or purplish plaques or nodules.
- Biopsy shows inflammation that is composed mainly of neutrophils without vasculitis.
- Preceding fever or infection.
- Accompanying fever, painful joints, conjunctivitis, or underlying cancer.
- Raised white cell count on blood testing.
- Improvement with systemic steroids and not with antibiotics.
- Increased erythrocyte sedimentation rate (ESR).
Diagnostic histopathological features of Sweet syndrome are numerous polynuclear neutrophil inflammatory cells on skin biopsy associated with broken-up neutrophils (leukocytoclasia) and swelling of cells lining blood vessels (endothelial cells). However other inflammatory patterns may be observed, eg mononuclear histiocyte cells rather than polynuclear neutrophil cells despite otherwise typical symptoms and signs of Sweet syndrome. True vasculitis may occur in severe cases.
Blood tests in patients with Sweet syndrome may reveal:
- Raised erythrocyte sedimentation rate (ESR) or C-reactive protein (CRP), indicating systemic inflammatory disease.
- Raised white cell count (neutrophil leukocytosis).
- p-ANCA (antineutrophil cytoplasmic antibody) or c-ANCA is sometimes present.
Occasionally Sweet syndrome is the presenting sign of a serious blood condition. A full blood count may reveal raised or reduced numbers of red cells, white cells and/or platelets. Further investigation may require bone marrow examination.
Oakley, A. (2015) Acute Febrile Neutrophilic Dermatosis. DermNet NZ (online). Published 1998, and updated Sept 2015.
Further information – patients.
Three Unusual Cases of Sweet’s Syndrome Where Skin Lesions Where the Only Symptom. In Case 3, ESR and CRP were normal.
Variants of Sweet’s Syndrome. Sometimes, Sweet’s syndrome can occur in an unusual form, and this is known as a disease variant. If you have a variant of Sweet’s syndrome, this can make it more difficult to diagnose.
Further information – medical.
Cohen, P. (2007) Table 1: Diagnostic criteria for classical Sweet’s syndrome versus drug-induced Sweet’s syndrome. In Sweet’s syndrome – a comprehensive review of an acute febrile neutrophilic dermatosis (online).
Deng, S., Zhang, B., Sui, X., Sang, S. and Zhang, W. (2016) Elevated 18F-FDG Uptake in Skeletal Muscles Rather Than Cutaneous Foci in a Patient With Sweet’s Syndrome. Clinical Nuclear Medicine, Oct 5th (PubMed).
Gaopande, V., Joshi, S. and Josh, A. (2015) Acute promyelocytic leukemia-associated Sweet’s syndrome mimicking an axillary abscess: A case report with review of literature. Diagnostic Cytopathology, Sept 21 (PubMed). This is possibly the first case of Sweet’s syndrome being diagnosed via fine-needle aspiration biopsy.
Kaballo, M. (2016) Sweet’s Syndrome and the Kidney. Renal Fellow Network, Apr 18 (online). Includes information on possible causes for a positive ANCA test in Sweet’s syndrome.
Soon, C., Kirsch, I., Connolly, A., Kwong., B. and Kim, J. (2016) Eosinophil-Rich Acute Febrile Neutrophilic Dermatosis in a Patient With Enteropathy-Associated T-cell Lymphoma, Type 1. The American Journal of Dermatopathology, Apr 19 (PubMed).
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