MCQ: Neonatal thrombocytopenia | Diagnosis
A newborn develops severe thrombocytopenia (platelet count 8 × 10⁹/L) with petechiae within 12 hours of birth. The mother’s platelet count is normal, and she has no history of autoimmune disease or medications causing thrombocytopenia. The baby is otherwise well. Platelet transfusion results in only a transient rise in platelet count. Further investigation reveals maternal antibodies against a specific platelet antigen present on paternal platelets.
Which of the following is the most likely diagnosis?
A. Autoimmune thrombocytopenia due to maternal ITP
B. Congenital amegakaryocytic thrombocytopenia
C. Neonatal alloimmune thrombocytopenia
D. Neonatal sepsis-associated thrombocytopenia
E. Thrombocytopenia due to disseminated intravascular coagulation
Correct answer & Explanation:
Correct answer: C. Neonatal alloimmune thrombocytopenia
Explanation:
Neonatal alloimmune thrombocytopenia (NAIT) results from maternal IgG antibodies directed against fetal platelet antigens inherited from the father. The most common target is HPA-1a (human platelet antigen-1a).
Clinical features:
- Severe thrombocytopenia often present at birth or within the first few hours of life
- Petechiae, purpura, and bleeding
- Intracranial hemorrhage may occur antenatally or after birth
- Mother has a normal platelet count
Diagnosis:
- Severe neonatal thrombocytopenia
- Detection of maternal anti-platelet antibodies
- Platelet antigen typing showing incompatibility between mother and fetus
Why other options are incorrect:
A. Autoimmune thrombocytopenia due to maternal ITP
- Maternal antibodies are against her own platelets and cross the placenta.
- Usually maternal history of ITP and maternal thrombocytopenia are present.
- Neonatal thrombocytopenia is usually less severe than NAIT.
B. Congenital amegakaryocytic thrombocytopenia
- Due to impaired megakaryocyte production (often thrombopoietin receptor mutations).
- Causes persistent thrombocytopenia but not maternal antibody-mediated disease.
D. Neonatal sepsis-associated thrombocytopenia
- Usually associated with clinical signs of infection and other abnormal findings.
- Platelet antigen antibodies are not present.
E. Disseminated intravascular coagulation
- Causes thrombocytopenia with abnormal coagulation profile and systemic illness.
Postgraduate pearl:
The severity of thrombocytopenia in NAIT is often greater than in neonatal autoimmune thrombocytopenia, and intracranial hemorrhage is the most feared complication, occurring in approximately 10–30% of affected infants.
