The goal

What did scientists want to find out?

Children make up only 5 percent to 10 percent of known PNH cases.

Studies of children with PNHParoxysmal nocturnal hemoglobinuria (PNH)A rare and chronic disease in which the body attacks and destroys its own red blood cells, which may result in anemia and blood clots. This process, called hemolysis, can lead to symptoms including fatigue, weakness, headaches, chest pain, abdominal pain and others. are few and far between.

In this study, scientists wanted to better understand how PNH may present differently in adults vs in children.

The method

How, where and when did they look for information to analyze?

The research team studied individuals who enrolled before June 2015 in the International PNH Registry. This is the largest available database of information about 3,681 people with PNH. Because the team wanted to study the natural course of the disease, they did not include anyone who was already being treated.

2,367 people in the Registry were eligible to be studied:

  • 2,268, almost 96 percent, were adults.

    The remaining 99, about 4 percent, were children who were younger than 18.

  • This study represents more children with PNH than all of the prior published research about PNH.

For each group, the researchers compared:

  • all of the bone marrowbone marrowThe soft fatty tissue inside certain bones that houses stem cells, some of which will ultimately become blood cells. Bone marrow provides the nutrients and environment needed for blood cells to be created. Once these cells are fully mature and ready to go to work, they leave the bone marrow and enter the bloodstream. disorders that people had

  • whether they experienced blood clots

  • kidney function

  • blood pressure

  • blood test results, like LDHLactate dehydrogenase (LDH)An enzyme found in the blood and tissues of the body, including the heart, kidneys, brain and lungs. Red blood cell destruction results in the release of LDH into the blood. People with PNH often have higher levels of LDH., hemoglobinhemoglobinThe critical protein found inside red blood cells that enables other cells throughout the body to get the oxygen they need. Hemoglobin acts like drops of glue that can “stick” to oxygen and carry it from the lungs to other tissues. It can also “stick” to waste like carbon dioxide to help remove it from the body. and complete blood countComplete blood count (CBC)A common blood test that analyzes the amount of red and white blood cells, hemoglobin and platelets in your blood. For people with PNH, red blood cell and hemoglobin levels are typically lower than normal.

They also assessed demographic characteristics, like age, race and gender, and clinical characteristics, like PNH clone sizeclone sizeThe percentage of red blood cells impacted by PNH. A large clone size means you have a high percentage of blood cells that can be attacked by the complement system, which may lead to more severe symptoms. .

The findings

What did the researchers learn?

The researchers found a number of differences between the children with PNH and the much larger group of adults:

  • Many children with PNH have smaller PNH clones than adults.

  • Children were also more likely to have severe cytopenia, which is when there are not enough mature blood cells in the bloodstream.

  • They were also more likely to have previous bone marrow aplasia, which is when the bone marrow doesn’t produce enough blood cells.

  • Children may experience more frequent bone marrow failure, but less severe hemolysishemolysisThe “breaking apart” of red blood cells. It can occur when the immune system attacks these cells as though they were dangerous viruses or bacteria. When red blood cells break open, hemoglobin is released. Hemolysis causes many of the symptoms of PNH.. They also had a lower rate of blood clots.

  • Blood in urine, LDH levels, and counts of immature red blood cells in children were significantly lower than in adults. This suggested that hemolysis was less severe — but children with PNH still seemed to experience hemolysis almost as often as adults.

  • The researchers assumed that many children with PNH have components that are both aplastic, which means there’s not enough red blood cells being produced, and hemolytic, which means red blood cells are being destroyed by the immune system.

  • The study confirmed that blood clots are an important concern in children with PNH, even though it seems to happen only half as often as in adults.

The takeaway

What did the researchers conclude from the study?

  • Bone marrow failure can progress to PNH. Therefore, the researchers concluded that children whose bone marrow does not produce enough red blood cells — even after immunosuppressive therapy — must be monitored for PNH
  • Future studies should examine long-term effects of PNH in both children and adults. They should also explore the impact of both anti-complement therapies and conventional methods to prevent blood clots
Please note: The information on this page is meant to be informational only and is not intended to replace medical advice. Always talk to your healthcare provider about any questions you may have on PNH, its symptoms or treatment.
  • Title: Letter to the editor: Different clinical characteristics of paroxysmal nocturnal hemoglobinuria in pediatric and adult patients
  • Journal: Haematologica 2017; 102:e76
  • Written by: Urbano-Ispizua, Á., Muus, P., Schrezenmeier, H., Almeida, A. M., Wilson, A., & Ware, R. E. (2017).