Mutations of nonmuscle myosin heavy chain 9 (MYH9) gene are an autosomal dominant cause of inherited thrombocytopenia in children. MYH9 spectrum disorders include May-Hegglin anomaly and Sebastian, Fechtner, and Epstein syndromes. Patients with these disorders often present with macroplatelets and thrombocytopenia and have a mild bleeding tendency; extrahematologic manifestations (nephropathy, deafness, and cataracts) correlate with specific mutations. No definitive guidelines exist for preoperative prophylactic platelet (PLT) transfusion in these patients.STUDY DESIGN AND METHODS:
This was a case study and literature review.RESULTS:
A 6-year-old male presented with appendicitis. Review of records revealed that he and his siblings had thrombocytopenia; polymerase chain reaction amplification with DNA sequence analysis showed a variation in the MYH9 gene previously reported as a known cause of MYH9-related disorders. Involvement of other organ systems was not found on initial work-up. The patient's PLT count on admission was 20 × 109/L. The degree of thrombocytopenia prompted transfusion of apheresis PLTs and he had good response (73 × 109/L). After infusion he developed hives, rash, itching, and nausea, which resolved after administration of epinephrine and hydrocortisone. Transfusion reaction work-up was negative and symptoms were interpreted as an allergic reaction. The appendectomy was uneventful.CONCLUSION:
This patient's PLT count was within guidelines to warrant transfusion; however, some patients with MYH9 mutations have counts above the transfusion threshold. To the authors' knowledge, there are no set guidelines for preoperative prophylaxis in a patient with an MYH9 deficiency. The management of the bleeding diathesis in these patients, especially in the setting of invasive procedures, is uncertain.