Harris Platelet Syndrome— Underdiagnosed and Unrecognized

To the Editor.—In the review article on Bernard-Soulier syndrome (BSS), Pham and Wang1 reported the May-Hegglin anomaly as the most common inherited giant platelet disorder. We disagree with the authors regarding that statement. To date, only 200 families, to our knowledge, have been studied for MYH9-related disorders. Harris platelet syndrome (HPS), previously called asymptomatic constitutional macrothrombocytopenia, is an inherited giant platelet disorder reported in healthy blood donors from the northeastern part of the Indian subcontinent.23 Cases of May-Hegglin have been reported from all around the world, with no particular geographic tendency. However, limited studies done on HPS have shown this entity to be prevalent predominantly in parts of the Indian subcontinent (the northeastern part of India and in Bangladesh, Bhutan, and Nepal).3 In this population, the incidence of HPS was shown to be higher than 30%.3 Harris platelet syndrome is an autosomal-dominant inherited giant platelet disorder characterized by mild (<150 × 103/μL) to severe (<50 × 103/μL) thrombocytopenia, giant platelets, normal platelet aggregation studies, and absent bleeding symptoms. No leukocyte or red blood cell abnormalities are detected. To date, there are no reliable blood tests to confirm this disorder. The differential diagnosis of inherited giant platelet disorder with minimal to absent bleeding symptoms includes heterozygous BSS and MYH9 disorders, gray platelet syndrome, and HPS. Although immunofluorescence analysis of neutrophil nonmuscle myosin heavy chain A serves as a screening test for MYH9 disorders, BSS is diagnosed by platelet-aggregation studies and flow cytometry.4Once these disorders are ruled out, we should consider the diagnosis of HPS, particularly if the patient is from the Indian subcontinent. Like BSS, HPS patients are also treated inappropriately with steroids and splenectomy. It is important to recognize HPS to avoid unnecessary investigation and treatment. Although HPS has been shown to be prevalent among people of a particular region, with the ongoing, global migration trend, it is plausible that this entity is being underreported.