Acute febrile neutrophilic dermatosis or Sweet syndrome
What is acute febrile neutrophilic dermatosis?
Acute febrile neutrophilic dermatosis is an uncommon skin condition characterised by fever and inflamed or blistered skin and mucosal lesions. Neutrophilic dermatoses are autoinflammatory conditions often associated with systemic disease.
Acute febrile neutrophilic dermatosis also has the eponymous name, Sweet syndrome or disease—named after Dr Robert Douglas Sweet from Plymouth, England, who first described it in 1964.
Who gets acute febrile neutrophilic dermatosis?
Acute febrile neutrophilic dermatosis most often occurs in middle-aged women, but men, children (rarely) and the elderly may also be affected. It has been found to be more common in individuals carrying the genetic marker HLA B54.
Acute febrile neutrophilic dermatosis may affect previously healthy individuals, but often arises in the context of an acute systemic infection or an underlying chronic condition.
What causes acute febrile neutrophilic dermatosis?
The exact cause of acute febrile neutrophilic dermatosis is unknown. Pro-inflammatory cytokines interleukin-1 and tumour necrosis factor alpha (TNFα) play a role.
Acute febrile neutrophilic dermatosis may follow:
- Sun exposure
- Upper respiratory tract infection (eg chest infection, streptococcal throat infection)
- Inflammatory bowel disease (eg ulcerative colitis or Crohn disease)
- Rheumatoid arthritis , lupus erythematosus and relapsing polychondritis
- Blood disorders including leukaemia (most often acute myelogenous leukaemia or myelodysplastic syndromes). These may cause histiocytoid Sweet syndrome (see above).
- Internal cancer usually of bowel, genitourinary organ or breast
- Gastrointestinal infection (eg campylobacter)
- Drugs, including azathioprine, granulocyte colony stimulating factor (G-CSF), nonsteroidal anti-inflammatory medications, cotrimoxazole and other antibiotics, TNFα inhibitors, carbamazepine and several others
In many people with acute febrile neutrophilic dermatosis, no underlying condition is found.
What are the symptoms of acute febrile neutrophilic dermatosis?
Acute febrile neutrophilic dermatosis may occur once or recur on several occasions. It is characterised by some or all of the following symptoms:
- High or moderate fever
- Tiredness and malaise (feeling unwell)
- Skin lesions
- Sore eyes and/or mouth ulcers
- Aching joints
- Sometimes other organs are affected, including bones, nervous system, kidneys, intestines, liver, heart, lungs, muscles and spleen.
What do the skin lesions look like?
Skin lesions of acute febrile neutrophilic dermatosis may be few in number or numerous. They are characteristically tender and may be extremely painful. They persist for days to weeks. The limbs and neck are the most commonly affected sites, but other areas of skin and mucosa may be involved. In some patients, they arise only in sun-exposed areas. Sweet syndrome lesions may have a range of appearances.
- Small papules (bumps) or vesicles (blisters)
- Larger thickened or swollen plaques (flat patches) or nodules (lumps)
- Pseudovesicular appearance (almost blistered)
- Annular (ring-shaped) lesions
- Erosions and ulcers resembling atypical pyoderma gangrenosum
Acute febrile neutrophilic dermatosis often causes erosions or ulcers inside the mouth, on the tongue or on the lips.
Ocular acute febrile neutrophilic dermatosis presents as a sore, red, sticky eye. It can lead to ulceration and loss of vision due to conjunctivitis, dacryoadenitis, keratitis, episleritis, scleritis, iritis, uveitis, glaucoma and choroiditis.
Subcutaneous acute febrile neutrophilic dermatosis
In subcutaneous acute febrile neutrophilic dermatosis, deeper, painful plaques develop on any area of skin. These may resemble cellulitis.
Neutrophilic dermatosis of hands
Neutrophilic dermatosis of the hands is considered a localised variant in which there are purplish nodules on the backs of the thumb, fingers and hand, or less often, on palmar surfaces.
Histiocytoid Sweet syndrome was first described in 2005. In this form of acute febrile neutrophilic dermatosis, instead of neutrophils, inflammation is associated with immature myeloid cell infiltration on biopsy. The name arises from the similar appearance of these monocytic cells to histiocytes. It can difficult to distinguish from leukaemia cutis.
The skin lesions in histiocytoid Sweet syndrome typically include multiple red, purplish or brownish oval shaped patches, plaques and nodules. The rash may be persistent but may improve with successful treatment of the underlying disease or withdrawal of causative medication.
Histiocytoid Sweet syndrome has been reported in:
- Myelodysplastic syndrome
- Myeloproliferative disorders including leukaemia
- Bortezomib-treated multiple myeloma
- Lymphocyte-predominant Hodgkin lymphoma
- Rheumatoid arthritis
How is acute febrile neutrophilic dermatosis diagnosed?
Acute febrile neutrophilic dermatosis may be diagnosed clinically, but at times it may be difficult to distinguish from infections such as chickenpox, or inflammatory conditions such as vasculitis. The diagnosis is usually confirmed on skin biopsy. Special stains may be necessary,
Diagnostic criteria for classic acute febrile neutrophilic dermatosis have been proposed.
Diagnostic histopathological features of acute febrile neutrophilic dermatosis are numerous polynuclear neutrophil inflammatory cells 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. True vasculitis may occur in severe cases.
Blood tests in patients with acute febrile neutrophilic dermatosis 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, acute febrile neutrophilic dermatosis 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.
What is the outcome of acute febrile neutrophilic dermatosis?
Acute febrile neutrophilic dermatosis resolves eventually, without leaving a mark or scar, with or without treatment.
Generally there is a single episode of Sweet syndrome, but a third of patients may develop recurrent episodes. This is more likely in patients who have underlying myelodysplasia or cancer. Rarely, it may persist for months or years.
Severe ulcerative cases associated with malignancy persist, despite treatment.
Treatment of acute febrile neutrophilic dermatosis
Treatment of acute febrile neutrophilic dermatosis usually results in rapid improvement in symptoms. Usually, systemic steroids, such as predniso(lo)ne, are prescribed in a dose of 30–60 mg daily. Within a few days the fever, skin lesions and other symptoms clear up. However, lower doses of corticosteroids are often required for several weeks to months to prevent relapse.
Several other medications may be tried when systemic corticosteroids are ineffective or contraindicated. Those reported to be useful include:
- Topical corticosteroids
- Intralesional corticosteroids
- Potassium iodide solution
- Non-steroidal anti-inflammatory drugs (indomethacin)
- Other biologic agents such as infliximab or etancercept
In some cases, acute febrile neutrophilic dermatosis is very resistant to treatment.
- Sweet's syndrome with hematologic disorders: a review and reappraisal. Buck T, González LM, Lambert WC, Schwartz RA. Int J Dermatol. 2008 Aug;47(8):775-82. Medline.
- Sweet’s Syndrome (Acute Febrile Neutrophil Dermatosis) – Derm101
- Chavan RN, Cappel MA, Ketterling RP, Wada DA, Rochet NM, Knudson R, Gibson LE. Histiocytoid Sweet syndrome may indicate leukemia cutis: A novel application of fluorescence in situ hybridization. J Am Acad Dermatol. 2014 Mar 14. pii: S0190-9622(14)01005-6. doi: 10.1016/j.jaad.2014.01.874.
- Pai S, Rytina E, Sterling J, Karas JA, Aliyu SH. Campylobacter gastroenteritis associated with Sweet's syndrome. J Med Microbiol. 2012 Oct;61(Pt 10):1473-5. doi: 10.1099/jmm.0.044412-0. Epub 2012 Jun 21. PubMed PMID: 22723255.
- Maalouf D, Battistella M, Bouaziz JD. Neutrophilic dermatosis: disease mechanism and treatment. Curr Opin Hematol. 2015 Jan;22(1):23-9. doi: 10.1097/MOH.0000000000000100. Review. PubMed PMID: 25394310.
- Cohen PR. Neutrophilic dermatoses: a review of current treatment options. Am J Clin Dermatol. 2009;10(5):301-12. doi: 10.2165/11310730-000000000-00000. Review. PubMed PMID: 19658442.
On DermNet NZ:
- Neutrophilic dermatoses
- Pyoderma gangrenosum
- Dermatological emergencies online course
- Neutrophilic dermatosis of the dorsal hands
- Pyoderma gangrenosum
- Sweet's Syndrome UK blog
- Acute Febrile Neutrophilic Dermatosis – Medscape Reference
- Sweet's syndrome – British Association of Dermatologists
Books about skin diseases:
See the DermNet NZ bookstore