Background and Importance Sweet syndrome (SS) is a rare febrile neutrophilic dermatosis characterised by edematous and erythematous papules, plaques or nodules on the skin, and fever. SS is associated with infection, malignancy, pregnancy and drug exposure. High doses of systemic glucocorticoids are the first-line treatment. Colchicine, dapsone, and potassium iodide are additional therapies, reserved for refractory cases. In addition, classic immunosuppressants have been effective. Newer case reports suggest benefit from biological therapies in recalcitrant cases.

We have found two other refractory SS cases in the literature.

Aim and Objectives To assess the effectiveness of adalimumab in a 50-year-old patient diagnosed with refractory idiopathic SS in a tertiary hospital.

Material and Methods In 2019, a man presented with fever, episcleritis, joint pain, and elevation of acute phase reactants (RFA) (C-reactive protein level (PCR), 35 mg/L; erythrocyte sedimentation rate (VSG), 48 mm; ferritin 416 ng/L). Early detection of autoimmune and infectious diseases was negative. Finally, he was diagnosed with idiopathic SS in 2022. Initially, colchicine was started without clinical response. Therefore, systemic glucocorticoids were initiated. The response was excellent, but he developed a central serous choroidopathy secondary to glucocorticoids, which contraindicated its use at high doses. Prednisone 5 mg daily was maintained. Later, dapsone was commenced but it was ineffective and caused haematological toxicity (anaemia). After dapsone withdrawal, anaemia blood markers improved. In April 2023, methotrexate 15 mg weekly and prednisone 10 mg daily were commenced. After two months, he presented skin lesions, fever, asthenia, arthralgia and elevated RFA (PCR, 46 mg/L; VSG, 84 mm; ferritin 603 ng/L). Considering it was a refractory SS, adalimumab off-label was requested.

Results On 5 July adalimumab 40 mg biweekly was initiated. Previously, informed consent was signed. Methotrexate and prednisone in descending doses were continued. After two injections, the disease had eased (no fever, skin lesions or inflammation) and without adverse effects. On 28 September, he started treatment with prednisone 5 mg daily, methotrexate 10 mg weekly and adalimumab 40 mg biweekly, and RFA are normal (PCR, <1 mg/L; VSG, 16 mm).

Conclusion and Relevance - Adalimumab is effective in the treatment of recalcitrant SS.

- A longer follow-up is needed to assess the effectiveness in the long term.

Conflict of Interest No conflict of interest.