title: Identification of inherited macrothrombocytopenias based on mean platelet volume among patients diagnosed with idiopathic thrombocytopenia.
abstract: Inherited macrothrombocytopenia is a rare illness that is often misdiagnosed as idiopathic thrombocytopenia (ITP), a more widespread acquired disease. Automated blood cell counters in routine clinical use usually miss giant platelets and underestimate mean platelet volume (MPV). Incorrect diagnoses might expose patients to a risk of unnecessary treatment. The ADVIA 120 hematology counter efficiently detects large platelets based on two-dimensional laser light scatter. The present study measures and re-evaluates MPV using the ADVIA 120 in 112 patients who had initially been diagnosed with ITP. We identified 11 unrelated patients as having probable macrothrombocytopenia (average MPV of 19.2+/-3.8 fL; normal range 7.8-10.2). Functional, phenotypical and DNA analyses confirmed that three of these patients had Bernard-Soulier syndrome and one had MYH9-related disease, both of which are the most common forms of inherited macrothrombocytopenia. We stress that a conventional automated hematology analyzer had overlooked giant platelets in these patients, and that all of them had received high-dose steroid therapy and/or splenectomy before this study according to a diagnosis of ITP. Thus, checking MPV using the ADVIA 120 in thrombocytopenic patients is a useful method of correctly diagnosing inherited macrothrombocytopenia, and thus avoiding patient exposure to unnecessary and sometimes toxic treatment.
authors.affiliation: Department of Medicine and Clinical Science, Gunma University Graduate School of Medicine, Maebashi, Japan.
authors.forename: Fumito
authors.initials: F
authors.lastname: Gohda
authors.forename: Hideki
authors.initials: H
authors.lastname: Uchiumi
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Handa
authors.forename: Takafumi
authors.initials: T
authors.lastname: Matsushima
authors.forename: Norifumi
authors.initials: N
authors.lastname: Tsukamoto
authors.forename: Kimio
authors.initials: K
authors.lastname: Morita
authors.forename: Hatsuo
authors.initials: H
authors.lastname: Amagai
authors.forename: Masami
authors.initials: M
authors.lastname: Murakami
authors.forename: Hirokazu
authors.initials: H
authors.lastname: Murakami
authors.forename: Yoshihisa
authors.initials: Y
authors.lastname: Nojima
authors.forename: Masamitsu
authors.initials: M
authors.lastname: Karasawa
mesh_terms: D000328:Adult; D000368:Aged; D001606:Bernard-Soulier Syndrome / Q000175:diagnosis; D001772:Blood Cell Count / Q000379:methods* / Q000592:standards; D001792:Blood Platelets / Q000473:pathology*; D048429:Cell Size; D003937:Diagnosis, Differential; D005260:Female; D006801:Humans; D007834:Lasers; D008297:Male; D008875:Middle Aged; D020409:Molecular Motor Proteins / Q000235:genetics; D018995:Myosin Heavy Chains / Q000235:genetics; D010976:Platelet Count; D012542:Scattering, Radiation; D013921:Thrombocytopenia / Q000097:blood / Q000175:diagnosis* / Q000209:etiology / Q000235:genetics*
chemical_list: C103814:MYH9 protein, human; D020409:Molecular Motor Proteins; D018995:Myosin Heavy Chains