Sweet's syndrome, or acute febrile neutrophilic dermatosis, was first described by Sweet RD in 1964. [1] This syndrome is characterized by the development of tender, erythematous plaques, fever, arthralgia and leukocytosis. [2] [3] The syndrome is reported to be associated with underlying infections, malignant neoplasms, pregnancy and drugs. [2] [3] In addition, Sweet's syndrome is also associated with autoimmune diseases. [2] [3] However, Sweet's syndrome associated with systemic lupus erythematosus (SLE) has been rarely reported. [4] [5] [6] Here, a case of simultaneously developed Sweet's syndrome and SLE in a man is reported.

A 48-year-old previously healthy man was admitted for intermittent fevers, arthralgias, and eruptions. He had never taken any meditations before occurrence of the symptoms. Laboratory investigations were C-reactive protein 2.31 mg/dL (normal range: <0.3 mg/dL), white blood cells 4300/mm3 with lymphocytes 830/mm3, CH50 18 U/mL (normal range: 30–46 U/mL), C3 37.0 mg/dL (normal range: 71–129 mg/dL), C4 5.7 mg/dL (normal range: 12–34 mg/dL) and immune complex 165.0 µg/mL (normal range: <3.0 µg/mL). Viral markers for hepatitis were negative. Antinuclear antibodies (ANA), anti-DNA antibodies were positive at 1:40 speckled pattern and 19 U/mL (normal range: <10 U/mL), respectively. Anti-SS-A antibodies, anti-SS-B antibodies, antineutrophil cytoplasmic antibodies against proteinase 3 and myeloperoxidase, anti-RNP antibodies, anti-Sm antibodies, anti-Jo-1 antibodies, anti-cardiolipin antibodies and lupus anticoaglant were all negative. Screening for malignancy by means of gallium scintigraphy, chest and abdominal computed tomography, and gastrointestinal fiberscope indicated no evidence of malignancy. Leukocytosis, which is a predominant feature of Sweet's syndrome, was not always observed in this case [1]. Rather, lymphopenia in addition to positive ANA and anti-DNA antibodies with hypocomplimentemia and high levels of immune complex in the serum were observed in this case. SLE was diagnosed based on the presence of arthritis, lymphopenia, ANA and anti-DNA antibodies according to the revised classification criteria of SLE.

A biopsy specimen from an erythematous papule from the right sole (Figure 1) showed a slight lichenification and an infiltration of neutrophils and lymphocytes in dermis without leukocytoclastic vasculitis (Figure 2A–B). Furthermore, immunofluorescence was positive for complement deposition at dermal-epidermal junction, indication a positive for lupus band test. This finding further helps to confirm the diagnosis of SLE. Oral administration of prednisolone was begun at a dose of 20 mg/day, resulting in diminishing skin eruptions and a resolution of arthralgia. Thus, this case met the modified criteria for Sweet's syndrome proposed by von den Driesch [1].

Sweet's syndrome is reported to be associated with underlying infections, malignant neoplasms, pregnancy, drugs, and autoimmune diseases. [2] [3] Thus, Sweet's syndrome is categorized into classical, drug-induced, and malignancy-associated form. We diagnosed this case as a classical Sweet's syndrome.

The characteristic histopathologic features of Sweet's syndrome are diffuse infiltrate of predominantly neutrophils with leukocytoclasia, papillary dermal edema, swollen endothelial cells and an absence of leukocytoclastic vasculitis. The pathological findings of this patient were consistent with Sweet's syndrome. In addition, immunofluoresence of immunoglobulin and complement deposition at the basement membrane of the skin was positive along with serum hypocomplementemia and high immune complex levels, suggesting a coexistence of SLE.

Concurrence of lupus including drug-induced lupus and subacute cutaneous lupus with Sweet's syndrome had been reported previously in adults. [7] [8] However, only three cases of concurrence of classical Sweet's syndrome and SLE have been reported, in whom two are women and one is a man. [4] [5] [6] Although both classical Sweet's syndrome and SLE predominantly occur in women, this is the second case of coincidence of classical Sweet's syndrome and SLE in an adult man.

Sweet's syndrome associated with SLE has been rarely reported. This is a second case of concurrence of classical Sweet's syndrome and SLE observed in a male patient.

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