Sweet syndrome (ORPHA:3243)
A rare inflammatory disease characterized by abrupt appearance of painful, edematous and erythematous papules, plaques and nodules on the skin, and frequently accompanied by fever and neutrophilia with a dense infiltration of mature neutrophils that are typically located in the upper dermis. The disease is classically associated with inflammatory disease, pregnancy, infection (mostly of the upper respiratory tract), or vaccination but may be idiopathic, associated with a hematological or visceral malignancy, or drug-induced.
Epidemiology
Several hundred cases of Sweet syndrome have been published.
Clinical description
Classical Sweet syndrome (CSS) usually presents in women between the age of 30 and 50 years. It is often preceded by an upper respiratory tract infection and may be associated with inflammatory bowel disease. It is characterized by the abrupt onset of painful erythematous plaques or nodules, but pustules and bullae are also described. Fever is observed in 30 to 80% of cases. Approximately one-third of patients with CSS experience recurrence of the dermatosis. Malignancy-associated Sweet syndrome (MASS) can occur as a paraneoplastic syndrome in patients with an established cancer or individuals whose Sweet syndrome-related hematologic dyscrasia or solid tumor was previously undiscovered; MASS is most commonly related to acute myelogenous leukemia. The dermatosis can precede, follow, or appear concurrently with the diagnosis of the patient's cancer. Hence, MASS can be the cutaneous harbinger of either an undiagnosed visceral malignancy in a previously cancer-free individual or an unsuspected cancer recurrence in an oncology patient. Drug-induced Sweet syndrome (DISS) most commonly occurs in patients who have been treated with granulocyte-colony stimulating factor, however, numerous medications have also be associated with DISS.
Etiology
The pathogenesis may be multifactorial and still remains to be definitively established. Clinical and laboratory evidence suggests that altered expression of inflammatory effector molecules, abnormal neutrophil function and genetic predisposition have an etiologic role.
Diagnostic methods
Sweet syndrome (SS) is a diagnosis of exclusion and is based on criteria (both of the major and 2 minor criteria are required for diagnosis). Major criteria include 1) abrupt onset of typical cutaneous lesions and 2) histopathology consistent with SS. Minor criteria include 1) lesions preceded by one of the associated infections or vaccinations; accompanied by one of the associated malignancies or inflammatory disorders; associated with drug exposure or pregnancy, 2) presence of fever and constitutional signs and symptoms, 3) leukocytosis, and 4) excellent response to systemic corticosteroids.
Differential diagnosis
Differential diagnosis includes infectious disorders, inflammatory disorders (e.g. arthropod bites, halogenoderma, other neutrophilic dermatoses, Wells syndrome), and neoplastic disorders (e.g. leukemia cutis, lymphoma cutis, metastatic carcinoma).
Management and treatment
Management of SS need to take into account any associated-diseases or medications. Systemic corticosteroids are the therapeutic gold standard. After initiation of treatment with systemic corticosteroids, there is a prompt response consisting of dramatic improvement of both the dermatosis-related symptoms and skin lesions. Topical application of high potency corticosteroids or intralesional corticosteroids may be used for treating localized lesions. Other first-line oral systemic agents are potassium iodide and colchicine. Second-line oral systemic agents include indomethacin and dapsone. TNF alpha inhibitors and the IL-1 receptor antagonist (anakinra) have been used in case reports.
Prognosis
The symptoms and lesions may resolve spontaneously, without any therapeutic intervention; however, recurrence may follow either spontaneous remission or therapy-induced clinical resolution.

                            Last update: 
                            August 2020


                            - Expert reviewer(s): 
                            Pr Emmanuel DELAPORTE