Updated on August 17, 2026.
Paroxysmal nocturnal hemoglobinuria (PNH) is a rare blood disorder where the immune system attacks and destroys blood cells. The underlying causes are acquired genetic mutations, meaning they are not inherited from biological parents.
The underlying causes of PNH are complex, but in simple terms it causes blood-forming cells in the bone marrow to produce defective blood cells. The defects in these blood cells attract the attention of immune cells, resulting in blood cell destruction, inflammation, damage to blood vessel walls, and other problems. One of the most common symptoms is dark or blood-colored urine, often when emptying the bladder in the morning after sleep. This is caused by large amounts of hemoglobin (a protein released when red blood cells are destroyed), being filtered from the blood and into urine.
PNH reduces the amount of healthy blood cells in the body and can cause a number of problems depending on the severity of the disease. Mild disease can involve anemia, and symptoms like fatigue, shortness of breath, chest pain, and rapid heartbeat. More severe cases can cause difficulty with swallowing, painful muscle spasms, debilitating fatigue, and erectile dysfunction. Life-threatening complications can occur, the most common being blood clots.
What are the treatment options for PNH?
The only potential cure for PNH is an allogenic stem cell transplant (bone marrow transplant), but this procedure carries a high risk of serious side effects and requires a matching stem cell donor. It is only recommended in cases of severe, life-threatening PNH.
Most cases of PNH are managed with medications called complement inhibitors. These medications act on the complement system (part of the immune system) and reduce the immune activity involved in blood cell destruction.
A treatment plan can also include anticoagulants (blood thinners) to treat blood clots, blood transfusions to treat anemia, iron supplementation, folic acid supplementation, and other supportive therapies.
Questions to ask when starting a new drug therapy
If you or a loved one is living with PNH, it’s important to have a thorough understanding of the therapies that your healthcare provider has prescribed. Use this list of questions any time you are prescribed a new medication.
- What is the name of the therapy?
- What dosage am I being prescribed?
- How does this therapy work to treat PNH?
- What are the goals of using this therapy?
- How is the medication administered? For example, will I be taking a pill? Will I be going to a hospital or center for infusions? Will I need to learn how to self-administer an injection?
- How will we know if this treatment is working? What kind of follow-up appointments will I need and how often?
- Are there things I will need to avoid during this part of treatment?
- What will this therapy cost? Who can I talk to if I have concerns about the cost?
- What treatment options do I have if this therapy doesn’t work?
Questions about possible side effects
PNH therapies cause side effects, and it’s important to discuss side effects before starting any treatment. Ask your healthcare providers:
- What side effects are common with this therapy?
- Is there a risk of serious side effects? For example, complement inhibitors come with an increased risk of serious infections that affect the brain and spinal cord.
- What can be done to reduce or manage side effects? Do I need any vaccines to protect against infections before starting treatment?
- What changes—in symptoms, in how I feel—do I need to watch for? When should you seek emergency care? Who should I contact if I have an emergency?
Your healthcare providers should have an up-to-date list of all medications you are taking. Your list should include all prescription medications, over-the-counter medications, and supplements (including herbal products).
Remember, your healthcare providers will be your best source of information about your diagnosis and your treatment options.
