SWEET SYNDROME; This spontaneous report was received from literature:  This report concerned a 44 year old female of unspecified race and ethnicity. Objective of this study was to present the case of acute febrile neutrophilic dermatosis (Sweet syndrome  SS) after Ad26.COV2.S vaccination against SARS-CoV-2.  The patient's height, and weight were not reported. The patient's pre-existing medical conditions included: The patient did not have any concomitant diseases. The patient received covid-19 vaccine ad26.cov2.s (suspension for injection, route of admin, and batch number were not reported, expiry: unknown) dose was not reported, 1 total (Doe 1), start therapy date was not reported for covid-19 prophylaxis. The batch number was not reported. Per procedure, no follow-up will be requested for this case. No concomitant medications were reported.  The patient was referred from emergency department and was admitted for a febrile mucous and skin eruption. The first symptoms occurred 2,5 months prior to the admission and included sore throat and painful lesions within the oral mucosa. The patient was treated with topical antiseptics, antifungals and NSAIDs, as well as systemic antibiotics and antifungals without remission. 5 days before the hospitalization, the patient additionally developed fever (up to 38,9°C), pain of the joints and muscles, painful nodular erythema of the feet and scattered skin lesions within the limbs. The physical examination revealed tender purulent vesicles and well demarcated edematous plaques consisting of papules and vesicles on the limbs. In the oral cavity erosions on the sides of the tongue and in the vestibule were present and the tongue was covered with yellowish coating. In the laboratory results the C-reactive protein (CRP) level was 92 mg/dl, white blood cell count (WBC) was 9,72x103/µl with neutrophilia 87,1%. The patient also suffered from mild microcytic anemia. Infectious causes were excluded prior to admission. The cultures (pustule, oral cavity and urine) were negative. The skin biopsy was taken from edematous plaque and nodular erythema of the feet. The histopathologic report confirmed the diagnosis of Sweet syndrome (acute febrile neutrophilic dermatosis. The possible neoplastic causes were examined [CA 125 (Carbohydrate antigen 125), CEA (Carcinoembryonic antigen) , CA 19-9 (Carbohydrate antigen 19-9), CA 15-3 (Carbohydrate antigen 15-3)], not revealing any abnormalities. Low level of ß-hCG (human chorionic gonadotropin) excluded pregnancy. HIV, lupus anticoagulant, pANCA (antineutrophil cytoplasmic antibodies), cANCA (antineutrophil cytoplasmic antibodies), anticardiolipin antibodies were negative. Antinuclear antibodies titer occurred to be 1:640, however immunoblot was negative. Direct immunofluorescence has not revealed any pathologic deposits. The patient was treated with oral prednisone 0.6 mg/kg/day and intravenous doxycycline 200 mg/day. The pain was relieved with subcutaneous tramadol 200 mg/day and 3% ichthyol solution was applied topically on nodular erythema. After 3 days of treatment there was a spectacular improvement in terms of both signs and symptoms, which additionally confirmed the diagnosis.  The action taken with covid-19 vaccine ad26.cov2.s was not applicable. The outcome of sweet syndrome was not reported. The authors emphasized sweet syndrome depicts a wide range of skin and mucous lesions that may be present in acute febrile neutrophilic dermatosis (nodular erythema, edematous plaques, pustules and erosions in oral cavity), yet its initial picture limited to mucous membranes, made it very challenging to settle the diagnosis. Early diagnosis of Sweet syndrome was important as it allows to avoid incorrect treatment and associated adverse effects, especially due to the fact that the proper therapy leads to very quick resolution of the skin changes.  This report was serious (Hospitalization Caused / Prolonged).; Sender's Comments: V0: 20221037130 - covid-19 vaccine ad26.cov2.s-Sweet syndrome. The event(s) has a compatible/suggestive temporal relationship, is unlabeled, and has unknown scientific plausibility. There is no information on any other factors potentially associated with the event(s). Therefore, this event(s) is considered unassessable.