Sweet syndrome is one of the forms of neutrophilic dermatosis, which is characterized by an island–inflammatory recurrent course. The main manifestations of this disease are pink or bright red plaques, fever, neutrophilia, joint pain. The diagnosis of Sweet syndrome is made on the basis of the clinical picture, histological examination of the skin, laboratory tests (blood test, biochemical examination, ELISA). Currently, etiotropic treatment has not been developed, anti-inflammatory therapy with corticosteroids and nonsteroidal anti-inflammatory drugs is used.
Sweet syndrome (acute febrile neutrophilic dermatosis) is a fairly rare acute dermatological disease that has a wave-like course. R. Sweet was the first to identify and describe this pathology in 1964, since then this dermatosis has been named after him. The prevalence of pathology is 1-9 cases per 1 million population. Basically, the Sweet syndrome affects older people (the average age is 56 years), occurs mainly in women – the sexual distribution is 3:1. According to other data, more than 90% of all cases are female, and a case of pathology development during pregnancy is described. The relationship between the occurrence of Sweet syndrome and a number of other pathologies – hematological, infectious and endocrine – has been noted. Cases are also described when the development of neutrophilic dermatosis preceded the appearance of malignant tumors.
The etiology of Sweet’s syndrome is currently unknown for sure, there are assumptions about an atypical immunological reaction in which there is no classical activation of the complement system. Stimulation of the immune system is presumably produced by bacterial, tumor or viral antigens that form complexes accumulating in tissues. After that, it is possible to develop an Arthus-type hypersensitivity reaction and a direct effect on inflammatory cells with the release of a significant amount of mediators. Histochemical studies have revealed that in skin plaques with Sweet syndrome there is a significant (tens and hundreds of times) increase in the concentration of interleukin-6 and colony stimulating factor of granulocytes. However, this may be due to acute inflammation that occurs with such a lesion of the dermis.
In most cases, Sweet syndrome occurs shortly after an acute respiratory infection. Streptococcal lesions, yersiniosis, ulcerative colitis, autoimmune diseases (in particular, Hashimoto’s thyroiditis, Crohn’s disease) can also act as a factor provoking dermatosis. In about 20% of cases, Sweet’s syndrome is a paraneoplastic reaction to the presence of a malignant hematological disease (acute myeloid leukemia) or solid tumors of the breast, gastrointestinal tract, genitourinary organs. In dermatology, patients with this type of dermatosis who have suffered oncological diseases in the past are quite common.
Currently, several forms of Sweet syndrome have been studied, which differ among themselves by factors that provoke the development of pathology.
- The classical or idiopathic form is the most common (almost 80% of patients), occurs shortly after a respiratory disease or against the background of autoimmune lesions, yersiniosis, ulcerative colitis.
- Sweet syndrome associated with paraneoplasia is a rarer form (less than 20% of all cases), most often occurs with myeloblastic leukemia and other malignant hematological diseases. It can also develop due to breast cancer or a tumor of the gastrointestinal tract. In some cases, the development of dermatosis occurs many years after treatment and remission of cancer.
- Sweet’s syndrome caused by taking certain medications is the rarest type of disease that can occur against the background of taking granulocyte colony stimulating factor. There are separate indications of the appearance of dermatosis after taking furosemide, minocycline and hydralazine.
The first sign of Sweet syndrome is the appearance of papules with a diameter of 2-8 millimeters on the surface of the skin. Spots of bright red color are located on the arms, chest, neck. Then, after 2-3 days, a significant increase in temperature (up to 40 degrees), fever, joint pain joins. The formation of papules continues, which 7-10 days after the appearance of the first symptoms of Sweet syndrome begin to merge into irregular plaques with a diameter of up to 7 centimeters. Itching of the skin in the places of the appearance of rashes throughout the disease has an average intensity or is not observed at all. In rare cases, multiple papules occur immediately on the entire surface of the body, which indicates a generalized form of Sweet syndrome.
Over time, against the background of treatment or spontaneously, plaques begin to resolve – the swelling of the skin decreases, the intensity of coloring decreases. As a rule, with Sweet syndrome, such processes begin in the center of the plaques, so for a while they take a ring-shaped shape, and then they look like arcs. After the complete attenuation of inflammatory processes, areas of hyperpigmentation of the skin that persist for a long time often remain at the site of rashes. Sweet’s syndrome is characterized by a recurrent course, so it is possible to resume arthralgia and fever, the reappearance of papules and plaques in the same areas that were previously affected.
The main methods of diagnosing Sweet syndrome are dermatological examination, general and biochemical blood analysis, in some cases, a skin biopsy is performed in the affected area. When examined by a dermatologist, the disseminated nature of the rashes is revealed, but their distribution is usually symmetrical. The presence of papules and plaques at different stages of their development is detected. It is possible to have hyperpigmented skin areas that remain from past attacks of Sweet syndrome. Palpation reveals a denser roller in the structure of the plaques along the edges of the formation. Objectively, an increased body temperature is also detected, patients complain of joint pain.
Blood test for Sweet syndrome shows pronounced neutrophilic leukocytosis – the total number of leukocytes can reach 10-12 x 109 / l, of which the proportion of neutrophils of all types is 60-70%. It is also often observed an increased level of monocytes, an acceleration of the rate of erythrocyte sedimentation. Biochemical analysis reveals a slight increase in the level of liver enzymes (AST and ALT), sometimes a decrease in total protein. In addition, in the presence of Sweet syndrome, it makes sense to conduct a study on the level of the main cancer markers, antibodies to yersiniosis and streptococcal infections – in some cases, these tests may be positive.
Histological examination of the tissues of skin plaques that occur with Sweet syndrome shows unchanged epidermis, edema of the dermis, capillary dilation and neutrophil infiltration. Differential diagnosis should be carried out with urticaria, nodular and multiform exudative erythema, sometimes systemic lupus erythematosus.
Treatment, prognosis and prevention
Etiotropic therapy of Sweet syndrome does not exist at the moment, treatment is performed with anti–inflammatory drugs – glucocorticoids (prednisone), nonsteroidal anti-inflammatory drugs (indomethacin). A number of patients had a positive reaction to the use of dapsone (antimicrobial agent) and potassium iodide. Externally, glucocorticosteroids are also prescribed – in the form of a cream or ointment, the duration of treatment is 5-10 days.
The prognosis of Sweet syndrome is favorable, rashes with proper treatment quickly disappear, leaving behind only areas of increased pigmentation, arthralgia does not return after recovery. However, there is a risk of recurrence of the disease, on the same or new areas of the body. In addition, the development of Sweet syndrome is a reason for contacting an oncologist and conducting a comprehensive examination due to the risk of having a malignant tumor or hematological oncopathology.