National Center for Advancing and Translational Sciences Genetic and Rare Diseases Information Center, a program of the National Center for Advancing and Translational Sciences

Paroxysmal nocturnal hemoglobinuria

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Why does it appear that hemolysis occurs mostly at night?
The term "nocturnal" refers to the belief that hemolysis is triggered by acidosis during sleep. However, this observation was later disproved. In individuals with paroxysmal nocturnal hemoglobinuria, hemolysis has been shown to occur throughout the day, but the urine concentrated overnight produces the dramatic change in color.[1] It is most noticeable in the morning, upon passing urine that has accumulated in the bladder during the night.[2]
Last updated: 1/15/2011

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  1. Emmanuel C Besa and Ulrich Woermann. Paroxysmal Nocturnal Hemoglobinuria. eMedicine. March 27, 2009; http://emedicine.medscape.com/article/207468-overview. Accessed 1/15/2011.
  2. Paroxysmal nocturnal hemoglobinuria. Genetics Home Reference. May 2007; http://ghr.nlm.nih.gov/condition/paroxysmal-nocturnal-hemoglobinuria. Accessed 1/15/2011.