Fetal and neonatal alloimmune thrombocytopenia (FNAIT) and immune thrombocytopenia purpura (ITP) are both conditions that involve a low platelet count. In FNAIT and ITP a low platelet count causes the blood to stop clotting correctly, leading to bruising, uncontrolled bleeding and hemorrhage. However, that is where their similarity ends.
What is FNAIT?
Fetal and neonatal alloimmune thrombocytopenia (FNAIT) is a rare but serious condition that affects 0.1% of pregnancies in which a pregnant mother’s immune system produces antibodies against the platelets of her fetus. This occurs when a fetus inherits platelet antigens from the father that are not compatible with the mother, typically involving a protein called human platelet antigen (HPA).
The mother’s immune system recognizes the fetal platelets as foreign, attacking and destroying them, leading to low platelet levels (thrombocytopenia) in the fetus or newborn.
Symptoms of FNAIT may include:
- Petechiae or red and purple pinprick spots.
- Purpura or red purple or brown patches of skin discoloration.
- Bruises that are unexpected or hard to explain.
- Hematomas or large bruises that accumulate under the skin.
- Cephalohematoma, in which blood collects under the scalp.
- Bleeding that does not stop on its own.
- Intracranial hemorrhage, also known as bleeding on the brain.
- Bleeding from the eyes.
- Coughing up blood due to blood accumulation in the lungs.
Learn more about FNAIT signs and symptoms
What is ITP?
ITP is a rare blood platelet disorder that is also referred to as idiopathic thrombocytopenic purpura or immune thrombocytopenia. The body’s immune system slowly attacks blood platelets, causing thrombocytopenia and leading to numerous symptoms.
Symptoms from ITP are related to blood no longer clotting correctly and may include:
- Petechiae or red and purple pinprick spots that form a rash on your lower legs.
- Purpura or red purple or brown patches of skin discoloration.
- Bruises that are unexpected or hard to explain.
- Hematomas or large bruises that accumulate under the skin.
- Bleeding and swollen gums.
- Dark stools resulting from blood.
- Blood when urinating.
- Heavy menstrual bleeding.
- Frequent, heavy nosebleeds.
- Feeling tired.
- Long-lasting bleeding from a small cut.
- Bleeding on the brain.
Each case of ITP is different, with symptoms varying from mild to life-threatening.
Treatment of ITP includes lifestyle changes, avoiding certain medications, intravenous immunoglobulin (IVIG) and corticosteroids.
Comparing FNAIT and ITP
Both FNAIT and ITP happen due to actions of the immune system. In FNAIT, maternal antibodies attack the fetal blood platelets inherited from the father, and in ITP, the immune system attacks all blood platelets, progressively breaking them down and leading to an array of symptoms that are caused by blood that no longer clots correctly.
Here is a comparison table of the two autoimmune disorders.
| FNAIT | ITP | |
| Population | Fetus or newborn | Children (often short-term), adults (often chronic), pregnant women (doesn’t affect the baby) |
| Cause | Alloimmune disorder caused by incompatibility between pregnant mother and fetus’ platelet type inherited from the father. Maternal antibodies attack the fetus’s platelets. | Autoimmune disorder possibly triggered by viral infection. The immune system attacks the body’s platelets. |
| Treatment | The mother receives IVIG with or without steroids; newborns undergo platelet transfusions | IVIG and steroids, immunosuppressants if necessary, lifestyle changes, avoiding certain medications, |
| Outcomes | Can resolve completely if treated proactively and effectively or be potentially life-threatening if intracranial hemorrhage occurs | Generally not a life-threatening condition. Ongoing low platelet levels can be managed, some life-threatening risks involved with bleeding if it occurs on the brain |
| Incidence | Rare: affects 1 in 10,000 live births | Rare: reported in approximately 2 per 100,000 adults |
Sign up here to get the latest news, perspectives, and information about FNAIT sent directly to your inbox. Registration is free and only takes a minute.
