If you’ve been diagnosed with paroxysmal nocturnal hemoglobinuria (PNH), you may also experience other health conditions that commonly affect people with this blood disorder. Additionally, certain other conditions can sometimes develop first and increase the risk of PNH.

When a person has more than one disease at the same time, the conditions are known as comorbidities. Some conditions may be more likely to develop after another disease is already present. If a condition arises during the course of an existing disease or after its treatment, it’s considered a complication. For people with rare diseases like PNH, complications can occur from hemolysis, the breakdown of erythrocytes (red blood cells). Also, immune system dysfunction in PNH can lead to other complications, such as chronic inflammation.

Having a comorbidity or complication may make it harder for your health care team to diagnose or treat your PNH and may even influence your prognosis (the likely course of disease). However, understanding how other conditions are related to PNH can help you talk to your doctor about treatment options. Addressing these related conditions may help you feel better, improve your prognosis, and boost your overall health and quality of life.

Several conditions and complications can occur alongside or as a result of PNH.

1. Aplastic Anemia

Researchers have identified just one risk factor for PNH — being diagnosed with aplastic anemia. Over 10 percent of people with aplastic anemia will develop PNH, according to the Aplastic Anemia and MDS International Foundation.

Aplastic anemia is a disorder of the bone marrow, which is the soft, spongy tissue found inside certain bones. Within the bone marrow, stem cells make all the different types of the body’s blood cells (red blood cells, white blood cells, and platelets). In aplastic anemia, stem cells become damaged or abnormal, preventing them from making enough healthy blood cells. This is known as bone marrow failure.

PNH and aplastic anemia have many similarities. Researchers believe that both develop when a person’s immune system attacks stem cells. Additionally, these two conditions can lead to some of the same sets of symptoms. PNH may develop before or after aplastic anemia occurs.

In some cases, an allogeneic bone marrow transplant (a type of stem cell transplant) may be considered as a treatment for PNH that occurs alongside aplastic anemia. However, this option carries significant risks. Talk to your health care team about the risks and benefits of bone marrow transplantation before making treatment decisions.

2. Myelodysplastic Syndromes

Myelodysplastic syndromes (MDS) are a group of bone marrow failure syndromes that happen in around 8 percent of people with PNH.

MDS also occurs due to problems with the bone marrow stem cells. Multiple forms of MDS lead to low levels of one or more types of blood cells. MDS is often thought to be caused by gene mutations (variants, or changes) and factors that can damage the genes, such as cancer treatments or exposure to certain chemicals. In some cases, MDS can progress to leukemia.

Because PNH and MDS both lead to drops in blood cell counts, they can cause some similar symptoms. A diagnosis of PNH may come before or after MDS develops.

3. Pulmonary Hypertension

About half of people with PNH also have pulmonary hypertension, which occurs when blood pressure levels rise too high within the blood vessels that connect the heart to the lungs. Pulmonary hypertension is a serious condition that needs early and proper treatment.

Symptoms include:

• Chest pain
• Fast heart rate
• Breathing difficulties
• Dizziness
• Sleepiness
• A blue, gray, or white tinge to skin

For people with PNH, pulmonary hypertension may develop as a complication of hemolysis. Red cells release hemoglobin, a protein, when they break apart. Hemoglobin can block another substance in the blood called nitric oxide, which is important for keeping blood pressure levels low. When nitric oxide levels drop due to hemolysis, pressure in your blood vessels may rise, potentially leading to pulmonary hypertension. Measuring lactate dehydrogenase (LDH) levels can track the severity of hemolysis, as higher LDH levels indicate more severe red blood cell destruction.

4. Blood Clots

At least one-third of people with PNH develop blood clots, which are considered the most dangerous complication of PNH. Blood clots are the leading cause of death for people with the disease.

Blood clotting is a natural part of your body’s healing process. This process, triggered by platelets, protects you from losing too much blood if you’re injured. However, blood clots become a problem if your body makes too many platelets, they form where they aren’t needed, or they don’t break down and go away.

In general, the most common blood clotting problems are deep vein thrombosis (a clot in a leg or an arm) or pulmonary embolism (a clot in the lungs). However, people with PNH are most likely to get blood clots in the brain or abdomen, including in the intestines or spleen. Blood clots typically produce a lot of pain and swelling in the affected area.

The risk of blood clots is one reason treatment with a complement inhibitor is often recommended for PNH. These medications work by preventing the complement system (a part of the immune system) from attacking red blood cells, reducing hemolysis and the chance of complications. However, these drugs can raise the risk of infections, and some may be inconvenient to take due to the need for regular infusions or injections. New oral forms (taken by mouth) such as iptacopan (Fabhalta) offer alternatives to infusion-based treatments.

PNH may also cause Budd–Chiari syndrome, a condition in which a blood clot forms in a vein within the liver. This can prevent the liver from working properly, leading to abdominal bloating, nausea, and pain or swelling in the upper right side of your abdomen.

Blood clots can cause serious health issues and are sometimes even life-threatening. You should contact emergency services right away if you think you’re experiencing signs of a clot.

5. Kidney Problems

Very rarely, PNH leads to kidney disease. It’s not clear why, but hemolysis can occasionally cause kidney injury, possibly . PNH may also cause blood clots to form in the kidneys’ blood vessels.

6. Leukemia

Some people with PNH develop acute myeloid leukemia (AML), a type of cancer that causes stem cells in the bone marrow to grow out of control. In AML, stem cells make high amounts of abnormal red blood cells, white blood cells, or platelet-producing cells.

Having AML as a comorbidity is rare — leukemia, in general, occurs in just 3 percent to 5 percent of people with PNH.

7. Meningitis

PNH is usually caused by a mutation in the PIGA gene. In very rare cases, the condition can result from a mutation in a different gene called PIGT and can include inflammatory symptoms like meningitis.

Meningitis is swelling of the tissue that surrounds the brain and spinal cord. It may cause fever, headache, a stiff neck, nausea, confusion, fatigue, or loss of appetite. Meningitis requires immediate medical care.

8. Inflammatory Bowel Disease

PNH may also lead to inflammatory bowel disease (IBD), although this is also very rare. IBD includes two conditions, ulcerative colitis and Crohn’s disease, which cause inflammation in different parts of the gastrointestinal tract. IBD causes abdominal pain, diarrhea, bloody stool, tiredness, and weight loss.

Talk With Others Who Understand

On myPNHteam, the site for people with paroxysmal nocturnal hemoglobinuria and their loved ones, members come together to ask questions, offer advice, and share their stories with others who understand life with PNH.

Do you have other health conditions besides PNH? Are they comorbidities or complications of PNH? Share your experience in the comments below, or start a conversation on your Activities page.