Pyknocytosis is a hematologic state characterized by the presence of pyknocytes in the blood. Pyknocytes are

red blood cells Red blood cells (RBCs), also referred to as red cells, red blood corpuscles (in humans or other animals not having nucleus in red blood cells), haematids, erythroid cells or erythrocytes (from Greek language, Greek ''erythros'' for "red" and ''k ...

that appear distorted, irregular and small with abnormal projections and would typically be identified by a medical scientist and verified by a

pathologist Pathology is the study of the causal, causes and effects of disease or injury. The word ''pathology'' also refers to the study of disease in general, incorporating a wide range of biology research fields and medical practices. However, when us ...

on a peripheral

blood smear A blood smear, peripheral blood smear or blood film is a thin layer of blood smeared on a glass microscope slide and then stained in such a way as to allow the various blood cells to be examined microscopically. Blood smears are examined in the ...

. Infantile pyknocytosis is the most commonly associated condition, and is a rare pediatric hematological condition. It is a potential cause of neonatal

hemolytic anemia Hemolytic anemia or haemolytic anaemia is a form of anemia due to hemolysis, the abnormal breakdown of red blood cells (RBCs), either in the blood vessels (intravascular hemolysis) or elsewhere in the human body (extravascular). This most commonly ...

. Infantile pyknocytosis typically presents with neonatal

jaundice Jaundice, also known as icterus, is a yellowish or greenish pigmentation of the skin and sclera due to high bilirubin levels. Jaundice in adults is typically a sign indicating the presence of underlying diseases involving abnormal heme meta ...

and severe anemia, often requiring

blood transfusions Blood transfusion is the process of transferring blood products into a person's circulation intravenously. Transfusions are used for various medical conditions to replace lost components of the blood. Early transfusions used whole blood, but mod ...

. The associated hemolytic anemia is often transient with peak incidence at 3–4 weeks, with spontaneous and complete resolution by four to six months of life. An

etiology Etiology (pronounced ; alternatively: aetiology or ætiology) is the study of causation or origination. The word is derived from the Greek (''aitiología'') "giving a reason for" (, ''aitía'', "cause"); and ('' -logía''). More completely, e ...

for this condition has not been established but some evidence, including the presence of dehydrated red cells on peripheral blood smear that seem to have undergone oxidative stress, points to causes that include deficiency of

antioxidants Antioxidants are compounds that inhibit oxidation, a chemical reaction that can produce free radicals. This can lead to polymerization and other chain reactions. They are frequently added to industrial products, such as fuels and lubricant ...

such as

vitamin E Vitamin E is a group of eight fat soluble compounds that include four tocopherols and four tocotrienols. Vitamin E deficiency, which is rare and usually due to an underlying problem with digesting dietary fat rather than from a diet low in vitami ...

or the presence of an oxidative factor. The diagnosis of infantile pyknocytosis is essentially based on the peripheral blood smear, with additional diagnostic investigations to rule out similarly presenting conditions such as

glucose-6-phosphate dehydrogenase deficiency Glucose-6-phosphate dehydrogenase deficiency (G6PDD), which is the most common enzyme deficiency worldwide, is an inborn error of metabolism that predisposes to red blood cell breakdown. Most of the time, those who are affected have no symptoms. ...

and

pyruvate kinase deficiency Pyruvate kinase deficiency is an inherited metabolic disorder of the enzyme pyruvate kinase which affects the survival of red blood cells. Both autosomal dominant and recessive inheritance have been observed with the disorder; classically, and mo ...

. Both of these conditions can also result in pyknocytes observable on the blood smear. Treatment involves phototherapy if blood

bilirubin Bilirubin (BR) (Latin for "red bile") is a red-orange compound that occurs in the normal catabolic pathway that breaks down heme in vertebrates. This catabolism is a necessary process in the body's clearance of waste products that arise from the ...

levels are greater than normal for the age of the infant, and blood transfusion if hemoglobin is found to be unacceptably low or decreasing based on clinical judgement of laboratory values.

References

Pediatrics Haemolytic anaemias {{Pediatrics-stub