Sweet’s syndrome (acute febrile neutrophilic dermatosis) is a rare inflammatory disorder affecting the skin and accompanied by systemic symptoms. The condition presents with a sudden onset of fever and a characteristic skin rash, signaling an overactive inflammatory response. Although the visible manifestations are typically the most striking feature, Sweet’s syndrome is a systemic condition involving more than just the skin.
Clinical Signs of Sweet’s Syndrome
The presentation of Sweet’s syndrome is marked by generalized symptoms and distinct skin lesions. Patients typically experience a sudden onset of high fever, often exceeding 100°F (38°C), and a general feeling of being unwell (malaise). Systemic involvement may also include headache, fatigue, and muscle or joint pain.
The dermatological manifestations appear as tender, red-to-violaceous plaques and nodules. These lesions are raised and often coalesce into larger, irregularly shaped patches. While they can appear anywhere on the body, the lesions most commonly affect the face, neck, and upper extremities, sometimes displaying a blister-like or target-like appearance.
The syndrome can affect other organ systems, known as extracutaneous involvement. The eyes are a frequent site, sometimes developing inflammation such as conjunctivitis or episcleritis. Other areas like the joints, kidneys, and lungs are less commonly affected.
Associated Conditions and Etiology
Sweet’s syndrome is generally understood to be a reactive process, meaning it is triggered by an underlying event or condition that causes an abnormal immune response. The condition is characterized by an accumulation of neutrophils (a type of white blood cell) in the dermis of the skin, which is the layer just beneath the surface. This dense neutrophilic infiltration is a defining feature, though the exact mechanism that causes this overreaction remains unknown.
The syndrome is broadly categorized into three main forms based on the context of its appearance. The classical or idiopathic form is the most frequent, where no specific cause can be identified. This classical form is often preceded by a mild infection, such as an upper respiratory tract or gastrointestinal infection, or can be associated with pregnancy or inflammatory diseases.
Malignancy-associated Sweet’s syndrome is a second category, accounting for up to 21% of cases. This form is most frequently linked to hematologic cancers, especially acute myeloid leukemia (AML). The syndrome may occur as a reaction to an established cancer, or it can be the first sign of an undiagnosed malignancy, making a thorough investigation important.
The third category is drug-induced Sweet’s syndrome, precipitated by exposure to certain medications. Granulocyte colony-stimulating factor (G-CSF) is the most commonly reported trigger. Other implicated agents include antibiotics like trimethoprim-sulfamethoxazole and various chemotherapy drugs.
Diagnosis and Treatment Protocols
Diagnosing Sweet’s syndrome relies on clinical observations and laboratory findings. Physicians look for the abrupt onset of the characteristic tender skin lesions combined with systemic symptoms like fever. Blood tests typically reveal an increased white blood cell count, particularly elevated neutrophils, and heightened inflammatory markers.
A skin biopsy is necessary to confirm the diagnosis and distinguish it from other skin conditions. Analysis shows a dense infiltration of mature neutrophils within the dermis, without evidence of the blood vessel damage seen in vasculitis. Fulfillment of established major and minor diagnostic criteria guides the physician toward definitive identification.
The goal of treatment is to quickly reduce inflammation and alleviate symptoms. Systemic corticosteroids, such as oral prednisone, serve as the first-line therapy for Sweet’s syndrome. Patients often experience improvement in both fever and skin lesions within days of starting this medication.
For patients who cannot tolerate corticosteroids or for resistant cases, alternative second-line treatments may be used. These options include medications such as colchicine or potassium iodide. While the condition often resolves well, recurrence can affect up to half of patients, particularly if an underlying cause like a malignancy is not addressed.