Sweet Syndrome Associated with Non-tuberculous Mycobacterial and Salmonella Co-Infection

Summary: Objectives: Sweet syndrome (acute febrile neutrophilic dermatosis) case associated with non-tuberculous mycobacterial (NTM) and Salmonella co-infection has not been reported to the best of our knowledge. Methods: We reported the clinicopathological features of Sweet syndrome associated with NTM and Salmonella co-infection in a 54-year-old man. We documented the clinical and histopathological findings and reviewed the literature about Sweet syndrome associated with atypical infections. Results: The patient presented with multiple erythematous plaques on the neck and forearm, followed by painful papules on fingertips and palms. He also had a fever and arthralgia. Skin biopsy demonstrated neutrophilic dermatitis consistent with Sweet syndrome. Laboratory findings showed marked leukocytosis (38.9K), elevated C-reactive protein (165.8 mg/L), positive ANA (1:640 speckled), and Salmonella bacteremia. Chest imaging revealed mediastinal lymphadenopathy and subsequent lymph node biopsy demonstrated acid-fast bacilli, confirming NTM infection. The patient responded well to systemic corticosteroids. Conclusions: This case highlights the importance of considering underlying systemic infections, including atypical infections, in patients presenting with Sweet syndrome. The co-occurrence of Sweet syndrome with dual NTM/Salmonella infection represents a previously unreported association, providing novel insights into the spectrum of infectious triggers in neutrophilic dermatoses.