Sweet syndrome

Sweet syndrome was named after a Dr Sweet from Plymouth, England, who first described this condition in 1964. It is also known as acute neutrophilic dermatosis.

In Sweet syndrome there is a sudden appearance of red tender lumps (plaques) on the skin usually of the limbs or neck, sometimes elsewhere. It most often occurs in middle-aged women, but men, children and the elderly may also be affected.

Sweet syndrome

What causes Sweet syndrome?

Sweet is a reaction to an internal condition. It may follow:

• Upper respiratory tract infection (e.g. chest infection, streptococcal throat infection)
• Vaccination
• Inflammatory bowel disease (e.g. ulcerative colitis or Crohn disease)
• Rheumatoid arthritis
• Blood disorders including leukaemia (most often acute myelogenous leukaemia or myelodysplastic syndromes).
• Internal cancer usually of bowel, genitourinary organ or breast
• Pregnancy
• Drugs, including granulocyte colony stimulating factor (G-CSF), nonsteroidal anti-inflammatory medications, cotrimoxasole and several others
• Immunodeficiency

In some people, no underlying condition is found.

What are the symptoms?

Sweet syndrome generally results in the following symptoms:

• High or moderate fever
• Tiredness and malaise (feeling unwell)
• One or more tender red papules or plaques. These enlarge and persist for several weeks. They may have blisters, pustules or ulcers. Sometimes they appear to clear in the centre.
• Aching joints and headache
• Sore eyes and/or mouth ulcers
• Sometimes other organs are affected including bones, nervous sytem, kidneys, intestines, liver, heart, lungs, muscles and spleen.

Sweet syndrome affecting mucosal surfaces

Skin lesions may arise at the site of injury such as a needle prick, biopsy or insect bite. It some patients they arise only in sun exposed areas.

Sweet syndrome is related to pyoderma gangrenosum, and is sometimes difficult to distinguish from it.

In one variant of Sweet syndrome, ‘neutrophilic dermatosis of the dorsal hands’, bluish or grey abscess-like nodules arise on the backs of the hands. These nodules may ulcerate. This is sometimes known as ‘pustular vasculitis’ of the hands, because inflamed blood vessels are seen on biopsy as well as an infiltration of neutrophil white cells.

Neutrophilic dermatosis of the dorsal hands

Investigations

Investigations 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) is sometimes present
• Numerous polynuclear neutrophil inflammatory cells on skin biopsy associated with broken-up neutrophils (leukocytoclasia) and swelling of cells lining blood vessels (endothelial cells)

Other neutrophilic dermatoses (skin conditions characterised by neutrophils) include pyoderma gangrenosum, neutrophilic eccrine hidradenitis, erythema elevatum diutinum and Behcet disease.

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.

Sometimes the cells seen on biopsy are mononuclear rather than polynuclear (histiocytoid) despite otherwise typical symptoms and signs of Sweet syndrome.

What is the outcome of Sweet syndrome?

Sweets' lesions resolve 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 underlyng cancer.

Treatment

Treatment usually results in rapid improvement in symptoms. Usually, systemic steroids (prednisone) are prescribed in a dose of 30-40 mg daily at first. Within a few days the fever, skin lesions and other symptoms clear up. However, lower doses of steroids are often required for several weeks to months to prevent relapse.

Several other medications may be tried when steroids are ineffective or contraindicated. These include: