Pyknosis, or karyopyknosis, is the irreversible condensation of chromatin in the nucleus of a cell undergoing necrosis[1] or apoptosis.[2] It is followed by karyorrhexis, or fragmentation of the nucleus. Pyknosis (from Greek pyknono meaning "to thicken up, to close or to condense") is also observed in the maturation of erythrocytes (a red blood cell) and the neutrophil (a type of white blood cell). The maturing metarubricyte (a stage in RBC maturation) will condense its nucleus before expelling it to become a reticulocyte. The maturing neutrophil will condense its nucleus into several connected lobes that stay in the cell until the end of its cell life.

Morphological characteristics of pyknosis and other forms of nuclear destruction

Pyknotic nuclei are often found in the zona reticularis of the adrenal gland. They are also found in the keratinocytes of the outermost layer in parakeratinised epithelium.

Another use of the word pyknotic is pyknotic objects in mathematics, which are hypersheaves on the site of compacta, which has nothing to do with nuclei.[3]

See alsoEdit


  1. ^ Kumar V, Abbas A, Nelson F, Mitchell R (2007). "Robbins Basic Pathology" (8th ed.): 6, 9–10 (table 1-1). {{cite journal}}: Cite journal requires |journal= (help)
  2. ^ Kroemer G, Galluzzi L, Vandenabeele P, et al. (January 2009). "Classification of cell death: recommendations of the Nomenclature Committee on Cell Death 2009". Cell Death Differ. 16 (1): 3–11. doi:10.1038/cdd.2008.150. PMC 2744427. PMID 18846107.
  3. ^ Barwick; Haine (2019). "Pyknotic objects, .I, basic notions". arXiv:1904.09966 [math.AG].