Paroxysmal Nocturnal Hemoglobinuria (PNH) is a rare blood disorder characterized by the destruction of red blood cells, leading to hemoglobin release into the urine, especially during the night. This occurs due to a mutation in the PIGA gene, which affects the surface proteins of blood cells, making them vulnerable to the immune system's attack. Symptoms of PNH can include dark-colored urine, fatigue, abdominal pain, and blood clots. Diagnosis typically involves blood tests to check for the presence of defective blood cells. Treatment options may include medications, blood transfusions, or bone marrow transplants, depending on the severity of the condition.