[Fasciitis-like primary breast pyoderma gangrenosum: A rare case report].

[INTRODUCTION AND IMPORTANCE] Pyoderma gangrenosum (PG) is a rare condition caused by dermal inflammation with neutrophilic infiltration, often associated with an underlying systemic disease. The breast is an uncommon site for this condition. It is an exclusion diagnosis, challenging to establish, which may initially lead to an alternative one and the initiation of inappropriate treatment.

[PRESENTATION OF CASE] A 41-year-old woman with a medical history of morbid obesity, breast reduction 14 years ago, common variable immunodeficiency (CVID), and autoimmune thrombocytopenia presented with a spontaneous inflammatory ulcer of the left breast. The clinical course rapidly deteriorated, progressing to septic shock despite antibiotics. This presentation led to the consideration of necrotizing soft tissue infection (NSTI) as the primary diagnosis. The patient underwent multiple surgical debridements combined with broad- spectrum antibiotic therapy, which resulted in only a slow improvement in her condition. Histopathological examination of the surgical specimens revealed a cutaneous ulcer with dermal inflammation predominantly composed of neutrophils. Her condition eventually stabilized, allowing for reconstruction of the left breast with a split-thickness skin graft. In the immediate postoperative period, the patient developed a fever of unknown origin and inflammatory lesions with a violaceous border at the graft donor site. PG was suspected. One month later, the patient presented with a spontaneously occurring violaceous inflammatory lesion on the controlateral breast.

[CLINICAL DISCUSSION] This case of spontaneous PG, is a condition only very rarely described in the literature. A combination of concordant findings support this diagnosis.

[CONCLUSION] PG is a rare condition with a challenging diagnosis, as it is one of exclusion. The breast is an uncommon site of involvement, typically described in postoperative cases and very rarely presenting spontaneously. When a patient presents with breast dermo-hypodermitis that shows limited improvement despite appropriate treatment, PG should be considered as a differential diagnosis.