2A 19 year old Bulgarian G2 P1 at 35 weeks by last menstrual period confirmed by ultrasound was found to have a platelet count of 40,000/µL during an admission for pyelonephritis. Past medical history was significant only for idiopathic thrombocytopenic purpura (ITP) diagnosed at age 12. She was followed by an oncologist at an outside facility and records showed that her baseline platelet count was 60,000/µL. She had no specific treatment except when she had been pregnant about 2 years prior, when she was placed on increasing doses of prednisone, reaching 50 mg/day, and intravenous immunoglobulin (IVIG) without a documented response of her platelet count. On presentation, she had no petechiae, ecchymoses, hepatosplenomegaly, or lymphadenopathy. Laboratory values were significant for a platelet count of 40,000/µL. Peripheral blood smear showed giant, gray pale platelets with a manual platelet count of 60,000/µL. Genomic DNA sequencing for MYH9 and NBEAL2 were revealing for a homozygous mutation for NBEAL2 and the diagnosis of Gray Platelet Syndrome was made. The patient was eventually delivered at 40 weeks by cesarean section, with an estimated blood loss of 1000mL. One unit of platelets was given prior to cesarean section for a platelet count of 40,000/µL; she was not given prednisone or IVIG pre‐operatively.
Gray Platelet Syndrome (GPS) is a very rare congenital disorder, with approximately 60 cases described to date. The syndrome is due to a gene mutation in NBEAL2 and is characterized by the absence of platelet alpha‐granules leading to gray platelets on light microscopy. It can be inherited in either an autosomal dominant or autosomal recessive manner and is often misdiagnosed as ITP, given its presentation as an isolated thrombocytopenia. In addition to large, pale gray platelets seen on peripheral smear, GPS differs from ITP in that it can often be associated with splenomegaly (whereas the finding of splenomegaly virtually excludes the diagnosis of ITP). Although our patient did not present with splenomegaly, careful examination of the peripheral smear would have suggested the diagnosis. Management for GPS is supportive and includes transfusions pre‐procedurally and for life‐threatening situations.
Our case highlights the importance that ITP is a diagnosis of exclusion. A peripheral blood smear is essential to confirm that the platelet count is truly low and not pseudothrombocytopenia due to platelet clumping. More importantly it can provide a clue for the diagnosis of a congenital or acquired thrombocytopenia. The harms of misdiagnosis of ITP are several. It can lead to the use of a variety of immunosuppressive agents that are associated with numerous mild to severe side effects. In addition, those misdiagnosed with ITP whose thrombocytopenia will invariably be refractory to medical management may be inappropriately referred for splenectomy.
To cite this abstract:Trang V, Lo N, Dietrich M, Shen Y. Did You Look at the Smear?. Abstract published at Hospital Medicine 2014, March 24-27, Las Vegas, Nev. Abstract 652. https://www.shmabstracts.com/abstract/did-you-look-at-the-smear/. Accessed February 16, 2019.