Hemolytic disease of the newborn

Not to be confused with Hemorrhagic disease of the newborn.

HDN
Classification and external resources
ICD-10	P55
ICD-9	773
DiseasesDB	5545
MedlinePlus	001298
eMedicine	ped/959
MeSH	D004899

Hemolytic disease of the newborn, also known as hemolytic disease of the fetus and newborn, HDN, HDFN, or erythroblastosis fetalis,^[1] is an alloimmune condition that develops in a fetus, when the IgG molecules (one of the five main types of antibodies) produced by the mother pass through the placenta. Among these antibodies are some which attack the red blood cells in the fetal circulation; the red cells are broken down and the fetus can develop reticulocytosis and anemia. This fetal disease ranges from mild to very severe, and fetal death from heart failure (hydrops fetalis) can occur. When the disease is moderate or severe, many erythroblasts are present in the fetal blood and so these forms of the disease can be called erythroblastosis fetalis (or erythroblastosis foetalis).

Symptoms

Hemolysis leads to elevated bilirubin levels. After delivery bilirubin is no longer cleared (via the placenta) from the neonate's blood and the symptoms of jaundice (yellowish skin and yellow discoloration of the whites of the eyes) increase within 24 hours after birth. Like any other severe neonatal jaundice, there is the possibility of acute or chronic kernicterus. Profound anemia can cause high-output heart failure, with pallor, enlarged liver and/or spleen, generalized swelling, and respiratory distress. The prenatal manifestations are known as hydrops fetalis; in severe forms this can include petechiae and purpura. The infant may be stillborn or die shortly after birth.^{[citation needed]}

Causes

Antibodies are produced when the body is exposed to an antigen foreign to the make-up of the body. If a mother is exposed to a foreign antigen and produces IgG (as opposed to IgM which does not cross the placenta), the IgG will target the antigen, if present in the fetus, and may affect it in utero and persist after delivery. The three most common models in which a woman becomes sensitized toward (i.e., produces IgG antibodies against) a particular antigen are:

• Fetal-maternal hemorrhage can occur due to trauma, abortion, childbirth, ruptures in the placenta during pregnancy, or medical procedures carried out during pregnancy that breach the uterine wall. In subsequent pregnancies, if there is a similar incompatibility in the fetus, these antibodies are then able to cross the placenta into the fetal bloodstream to attach to the red blood cells and cause hemolysis. In other words, if a mother has anti-RhD (D being the major Rhesus antigen) IgG antibodies as a result of previously carrying a RhD-positive fetus, this antibody will only affect a fetus with RhD-positive blood.

• The woman may receive a therapeutic blood transfusion. ABO blood group system and the D antigen of the Rhesus blood group system typing are routine prior to transfusion. Suggestions have been made that women of child bearing age or young girls should not be given a transfusion with Rhc-positive blood or Kell₁-positive blood to avoid possible sensitization, but this would strain the resources of blood transfusion services, and it is currently considered uneconomical to screen for these blood groups. HDFN can also be caused by antibodies to a variety of other blood group system antigens, but Kell and Rh are the most frequently encountered.

• The third sensitization model can occur in women of blood type O. The immune response to A and B antigens, that are widespread in the environment, usually leads to the production of IgM anti-A and IgM anti-B antibodies early in life. On rare occasions, IgG antibodies are produced. In contrast, Rhesus antibodies are generally not produced from exposure to environmental antigens.

Serological diagnoses

• ABO system
  • ABO hemolytic disease of the newborn can range from mild to severe, but generally it is a mild disease.
    • anti-A antibodies
    • anti-B antibodies
• Rhesus system
  • rhesus D hemolytic disease of the newborn (often called Rh disease) is the most common form of severe HDN. The disease varies from mild to severe.
  • rhesus E hemolytic disease of the newborn is a mild condition
  • rhesus c hemolytic disease of the newborn can range from a mild to severe disease - is the third most common form of severe HDN
  • rhesus e hemolytic disease of the newborn - rare
  • rhesus C hemolytic disease of the newborn - rare
  • antibody combinations (ie anti-Rhc and anti-RhE antibodies occurring together) - can be severe
• Kell system
  • anti-Kell hemolytic disease of the newborn
    • anti-K ₁ antibodies - disease ranges from mild to severe - over half of the cases are caused by multiple blood transfusions - is the second most common form of severe HDN
    • anti-K ₂ ,anti-K ₃ and anti-K ₄ antibodies - rare
• Other blood group antibodies (Kidd, Lewis, Duffy, MN, P and others).

Diagnosis

The diagnosis of HDN is based on history and laboratory findings:

Blood tests done on the newborn baby

• Biochemistry tests for jaundice
• Peripheral blood morphology shows increased reticulocytes. Erythroblasts (also known as nucleated red blood cells) occur in moderate and severe disease.
• Positive direct Coombs test (might be negative after fetal interuterine blood transfusion)

Blood tests done on the mother

• Positive indirect Coombs test

Treatment

Before birth, options for treatment include intrauterine transfusion or early induction of labor when pulmonary maturity has been attained, fetal distress is present, or 35 to 37 weeks of gestation have passed. The mother may also undergo plasma exchange to reduce the circulating levels of antibody by as much as 75%.

After birth, treatment depends on the severity of the condition, but could include temperature stabilization and monitoring, phototherapy, transfusion with compatible packed red blood, exchange transfusion with a blood type compatible with both the infant and the mother, sodium bicarbonate for correction of acidosis and/or assisted ventilation.

Rhesus-negative mothers who have had a pregnancy with/are pregnant with a rhesus-positive infant are given Rh immune globulin (RhIG) at 28 weeks during pregnancy, at 34 weeks, and within 72 hours after delivery to prevent sensitization to the D antigen. It works by binding any fetal red cells with the D antigen before the mother is able to produce an immune response and form anti-D IgG. A drawback to pre-partum administration of RhIG is that it causes a positive antibody screen when the mother is tested, which can be difficult to distinguish from natural immunonological responses that result in antibody production.

Complications and similar conditions

Complications of HDN could include kernicterus, hepatosplenomegaly, inspissated (thickened or dried) bile syndrome and/or greenish staining of the teeth, hemolytic anemia and damage to the liver due to excess bilirubin. Similar conditions include acquired hemolytic anemia, congenital toxoplasma and syphilis infection, congenital obstruction of the bile duct and cytomegalovirus infection.

In animals

Mule foal, 7-days-old, in the last stage of hemolytic disease; symptoms appeared only on Day 6

Hemolytic disease is a well-known condition in newborn foals, especially in Thoroughbreds and mules. Mares or jennies which have been sensitized by a previous pregnancy develop antibodies by fetal blood cells crossing the placental barrier. The iso-antibodies do not transcend the fetal barrier, but are present in colostrum. They will enter the bloodstream of the foal only after absorption of colostrum immunoglobulins, in the first days of life. Hence, hemolytic disaese will develop only after birth : first to 4th day in foal ^[2] and 3 to 7 days in newborn mules. Affected animals show lethargy, recumbency, tachycardia, and progressive icterus of eye and mouth mucosae, which rapidly leads to death. The condition is also described in newborn pigs and other animals ^[3]

See also

• Exchange transfusion

References

1. ^ "erythroblastosis fetalis" at Dorland's Medical Dictionary
2. ^ The Merck Veterinary Manual, 3rd ed. Merck and co. Inc. Rahway, N.J., USA, 1967.
3. ^ Hemolytic disaese in animals

External links

• Geifman-Holtzman, O; Wojtowycz M, Kosmas E, and Artal R (1997). "Female allo-immunization with antibodies known to cause hemolytic disease". Obstetrics and Gynecology 89 (2): 272–275. doi:10.1016/S0029-7844(96)00434-6. ISSN 0029-7844. PMID 9015034. 
• Mollison, PL; Engelfriet CP and Contreras M (1997). Blood Transfusion in Clinical Medicine (10th ed.). Oxford, UK: Blackwell Science. ISBN 0-86542-881-6. 
• Blood Groups and Red Cell Antigens: Hemolytic disease of the newborn