[A case of Sjögren's syndrome associated with EDTA-dependent pseudothrombocytopenia].

A 69-year-old woman was admitted to Department of Orthopedic Surgery in our hospital because of lumbago on April 4, 1995. Since laboratory data showed thrombocytopenia (platelet count 2.1 x 10(4)/mm3) on admission, she was transferred to Department of Internal Medicine for further examination on April 11. She noticed abnormal taste and showed remarkable sicca symptoms. Schirmer test, gum test and electrogustometry were positive, and parotid sialogram findings and histology of minor salivary glands of the lip were compatible with those of typical Sjögren's syndrome. Thus, she was diagnosed as Sjögren's syndrome. Although the antibodies to SS-A/SS-B were negative in her serum, anti-nuclear and anti-centromere antibodies were strongly positive (x1280). Serum IgM level was increased. The decreased platelet count was observed when EDTA was used as anticoagulant. The binding activity of the anti-platelet antibody activated by EDTA was dependent on temperature. Its immunoglobulin class was shown to be IgM by enzyme-labelled antibody method. We here report a case of Sjögren's syndrome associated with EDTA-dependent pseudothrombocytopenia.