Purpose Antiphospholipid syndrome (APS) is a severe and potentially life-threatening condition. Most commonly, it presents with arterial or venous thrombotic complications. Unusual presentations might lead to a delay in diagnostic and therapeutic measures. Purpura fulminans (PF) is a rarely reported manifestation.

Methods Case report at a single centre.

Results We present the case of a 25-year-old female who developed purpura fulminans after evacuation of a perimandibular abscess. The patient was initially admitted to an external maxillofacial surgery unit for incision and drainage of a perimandibular abscess after multiple episodes of tonsillitis. Her past medical history includes a significant spontaneous deep venous thrombosis 8 months prior to admission. APS had been suspected in view of one pathological lupus anticoagulant result, but a diagnosis had not been made at the time. The patient was anticoagulated with Rivaroxaban and had experienced no further events. Lupus serology remained negative. Immediately after maxillofacial surgery, the patient developed lightning bolt-shaped hematomas with peripheral blisters and central necrosis on both arms, her right thigh, the back of her neck and torso, as well as both earlobes.

She was diagnosed with PF and transferred to our rheumatology unit, where her medical management was adjusted with a switch from oral anticoagulation to low-molecular weight heparin and initiation of oral corticosteroid therapy. Further testing confirmed the working diagnosis of APS: a pathological lupus anticoagulant, raised anti-cardiolipin IgM and IgG, positive beta-2 glycoprotein, high aPTT, and low complement C3. A skin biopsy demonstrated multiple thrombi in blood vessels of the dermis. In light of this result and further clinical deterioration of the PF even under oral steroid therapy, treatment was escalated to five sessions of plasma exchange. With this treatment, the patient’s condition improved drastically. There were no further purpura or blisters and the existing skin lesions lightened and grew smaller. Anticoagulation was switched from heparin to Warfarin and the patient was discharged on a tapering dose of oral Prednisolone.

Conclusion PF is a rare presentation of APS. This case demonstrates the value of early and resolute escalation of treatment. Plasma exchange is a potentially life-saving treatment modality in this setting.