Paroxysmal Nocturnal Haemoglobinuria (PNH) is a very rare and debilitating disease of the bone marrow that affects the blood and major organs. It is a chronic, life-threatening illness and can have devastating effects upon a patient physically, mentally and emotionally.

PNH is an acquired illness caused by an injury to a bone marrow stem cell and is not hereditary. The bone marrow produces all blood cells for the body, being white cells, red cells and platelets. PNH occurs when a gene required for producing normal blood cells becomes mutated resulting in a PNH clone of bone marrow cells that produce defective blood cells. The white blood cells and platelets do not function as effectively as normal cells, leaving patients prone to infections and blood clots. While all three types of blood cells are affected by PNH, most of the symptoms experienced by patients are due to the destruction of red blood cells.

In people living with PNH, the red cells produced lack a protein called CD59, which would normally protect them from being destroyed by a substance in the blood called complement. Complement forms part of the immune system and is activated when cells foreign to the body are identified. When activated, complement has nine cascading levels of intensity to fight infection. Think of them as “bullets” which gradually increase in size.

The destruction of the red cells by complement is called haemolysis. Haemolysis occurs in everyone, as old blood cells are replaced by new ones. In people living with PNH, however, haemolysis usually occurs much faster and outside the circulation (in places like the spleen and liver) s. When haemolysis occurs at a rate that causes haemoglobin to drop below normal levels, haemolytic anaemia occurs. It was originally thought that the red cell destruction occurred during an attack, called a haemolytic crisis at night –  hence the name “paroxysmal nocturnal” – however it has been proven that haemolysis occurs constantly. The rate of hemolysis, or destruction of the cells, varies between patients and usually relates to the severity of symptoms experienced.

A red blood cell contains, among other substances, proteins and red haemoglobin pigment. When the cell is destroyed the haemoglobin that is released into the circulation is converted by the liver into bilirubin that, in excess, is deposited in the eyes and skin, causing jaundice. The haemoglobin pigment is also excreted quickly through the kidneys, resulting in “haemoglobinuria” which literally means haemoglobin in the urine.

Red blood cell destruction results in lowered haemoglobin levels, otherwise called anaemia. Red blood cells carry oxygen to the body’s organs and muscles, therefore lowered haemoglobin places added pressure upon organs, particularly the heart and lungs, and reduces muscular strength and stamina.

PLEASE NOTE: This information has been prepared by members of the PNHSAA Inc and has been checked for accuracy by practitioners experienced with PNH. The PNHSAA Inc does not guarantee its accuracy; it is intended as general information only and not to be substituted for medical advice. Please consult your medical practitioner for further information regarding your personal circumstances.