Condition confusion: Solving the PNH diagnosis puzzle
Last updated Oct. 6, 2025, by Agata Boxe
Fact-checked by Joana Carvalho, PhD
Paroxysmal nocturnal hemoglobinuria (PNH) is a rare disease that is often not recognized until it has significantly progressed. The condition can take years to diagnose — a journey that can be filled with frustration and uncertainty.
Understanding why PNH is frequently mistaken for other conditions can help you advocate for yourself and pave the way to an accurate diagnosis.
Why PNH is often misdiagnosed
PNH symptoms, such as severe fatigue, dark urine, abdominal pain, and difficulty breathing, overlap with other conditions. They also rarely appear all at once, which makes the disorder easy to misdiagnose.
This delay in diagnosis can lead to a delay in treatment, which can worsen symptoms and increase the risk of complications such as blood clots or bone marrow failure. For instance, a person with unexplained anemia may be treated for iron deficiency for months before clots or other complications point to PNH.
PNH and overlapping conditions
PNH overlaps with aplastic anemia and myelodysplastic syndromes, both of which involve bone marrow dysfunction. Bone marrow disorders can also coexist or precede PNH, which adds to the diagnostic confusion.
PNH symptoms such as fatigue and anemia may also be attributed to other issues, such as iron deficiency, another condition, or lifestyle factors. Blood clots, muscle spasms, and pain can be mistaken as well for other conditions that cause these symptoms.
When to consider PNH
Despite these diagnostic issues, certain signs can suggest when testing for PNH may be appropriate. These include:
- signs of red blood cell destruction with no known cause
- unexplained blood clots
- dark or blood-colored urine
- bone marrow dysfunction
- severe fatigue not explained by other causes.
PNH diagnosis
The gold standard for diagnosing PNH is flow cytometry, a highly sensitive test that rapidly analyzes the physical and chemical characteristics of blood cells.
Other lab tests, such as blood tests measuring the levels of lactate dehydrogenase, a marker of red blood cell destruction, can play a supportive role in the diagnostic process but are not specific enough on their own. Bone marrow tests may be used in some cases.
Advocating for yourself
Because PNH is so rare and its symptoms overlap with those of other conditions, it can be challenging for doctors to recognize it. Advocating for yourself when you suspect you have PNH or another rare disease can make a difference.
Consider keeping a log to track your symptoms. If you experience persistent unexplained symptoms, you have the right to ask your doctor whether you may have a rare disease like PNH.
Don’t hesitate to get a second opinion if you have doubts about your current diagnosis or if you don’t think your current treatment is working.
PNH support groups and organizations, such as the PNH News Facebook group and PNH Global Alliance, can provide additional information. They may also help you find doctors experienced in treating rare hematologic diseases.
While recognizing PNH requires specialized expertise, access to the right tools, and patience to get an accurate diagnosis, advocating for yourself may help you get access to essential treatments faster.
PNH News is strictly a news and information website about the disease. It does not provide medical advice, diagnosis, or treatment. This content is not intended to be a substitute for professional medical advice, diagnosis, or treatment. Always seek the advice of your physician or other qualified health provider with any questions you may have regarding a medical condition. Never disregard professional medical advice or delay in seeking it because of something you have read on this website.