Fetal and neonatal alloimmune thrombocytopenia (FNAIT) is usually associated with symptoms related to bleeding: red or purple skin discoloration, severe bruising and prolonged bleeding. However, many organs may be involved in disease development, including the spleen.
Although spleen problems aren’t usually seen in patients with FNAIT, the organ plays a key role in platelet destruction.
The spleen-platelet connection
FNAIT is caused when there is a mismatch between the mother’s and the baby’s platelets during pregnancy. As a result, the mother’s immune system produces antibodies that cross over the placenta into the baby’s bloodstream. There, they bind to the fetal platelets, leading to their breakdown.
Read more about FNAIT signs and symptoms
The spleen is the major site of platelet destruction. One of its many jobs is to filter the blood to help remove waste. In most people, this means that the organ removes damaged or old platelets but leaves functioning ones in the bloodstream.
In patients with FNAIT, on the other hand, the spleen “reads” the antibody-bound fetal platelets and targets them for destruction. Once they enter the spleen, special cells engulf and break them down, resulting in thrombocytopenia.
Does FNAIT cause spleen damage?
Although the spleen is heavily involved in the development of FNAIT, problems with the organ are rarely reported in patients with the disease. In fact, many doctors look for spleen problems to help rule out FNAIT.
In some babies with other types of thrombocytopenia, the spleen traps platelets, preventing them from entering the circulation and carrying out their needed functions. The buildup of platelets in the spleen can cause it to become enlarged, which is known as splenomegaly.
In FNAIT, the spleen isn’t sequestering platelets, but is rather targeting and destroying them. Therefore, it’s uncommon to see splenomegaly in babies with FNAIT.
If your baby is born with thrombocytopenia and an enlarged spleen, your doctor should check for other causes including:
- Infections: Many different infections can lead to splenomegaly, as the spleen works overtime to help remove the pathogens. This can also lower platelet counts.
- Autoimmune diseases: Several autoimmune diseases, including lupus, can contribute to thrombocytopenia and an enlarged spleen. This condition is known as secondary immune thrombocytopenia.
- Bone marrow disorders: Platelets are made in the bone marrow. Therefore, disorders of the bone marrow often impact platelet production, which can also cause splenomegaly.
Because the symptoms of FNAIT can overlap with so many other conditions, ensuring your baby receives a complete workup can help improve timely diagnosis and treatment.
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