Introduction: Paroxysmal nocturnal hemoglobinuria Paroxysmal nocturnal hemoglobinuria: (par-uk-SIZ-muhl nok-TURN-uhl hee-muh-gloe-buh-NYOOR-ee-uh) A rare and serious blood disease that causes red blood cells to break apart. Paroxysmal means sudden and irregular. Nocturnal means at night. Hemoglobinuria means hemoglobin in the urine. Hemoglobin is the red part of red blood cells. A… (PNH) is a rare, acquired, non-malignant hematologic disease characterized by complement-mediated hemolysis hemolysis: (hi-MOL-uh-suss) The destruction of red blood cells. (with or without hemoglobinuria hemoglobinuria: (hee-muh-gloe-buh-NYOOR-ee-uh) The presence of hemoglobin in the urine. ), fatigue, increased susceptibility to thrombosis thrombosis: (throm-BOE-suss) A blood clot (thrombus) that develops and attaches to a blood vessel. , and bone marrow bone marrow: The soft, spongy tissue inside most bones. Blood cells are formed in the bone marrow. dysfunction. The development of complement inhibitors has transformed outcomes for patients with PNH, but patients may still experience pharmacodynamic breakthrough hemolysis (BTH), which can be caused by exposure to a complement amplifying condition (CAC), such as vaccination, infection, or surgery.
Materials and methods: A 13-member expert panel used a validated methodology (a RAND/UCLA modified Delphi panel) to develop consensus on how to classify pharmacodynamic BTH in patients with complement-inhibitor treated PNH. Physicians reviewed literature, rated the appropriateness of over 400 scenarios, and discussed the ratings at an in-person meeting.
Results: After the meeting, the panel agreed on 77% of scenarios. Here, we present the group's agreed-upon recommendations on how to manage BTH caused by a CAC, as well as provide a severity classification system for BTH and strategies to mitigate risk of BTH in special circumstances (e.g. vaccination, planned or unplanned surgery, and pregnancy).
Discussion: In general, as severity of BTH increased, experts agreed more interventions to manage the BTH were appropriate. These recommendations are based on clinical experience and opinion. Without clear data from randomized trials to guide the management of BTH, expert opinion can be useful to support patient care.