Autoimmune thrombocytopenic purpura with spuriously normal platelet count and ‘punch‐hole’ red cells

Abstract

A 67-year-old female who had a long history of autoimmune thrombocytopenic purpura on corticosteroid therapy was hospitalized because of worsening petechiae and bruises despite apparent normalization of the platelet count. Peripheral blood counts by automated blood cell analyzer (COULTER LH 750) showed: haemoglobin 158 g/l, platelet count 144 × 109/l and leucocyte count 11·4 × 109/l with neutrophilia. However, blood film examination showed a paucity of platelets with an estimated manual platelet count of only 12 × 109/l. Furthermore, the red cells showed the occasional presence of ‘punch-holes’ in their cytoplasm, sometimes resembling a ‘bite-cell’ (left panel). Careful scrutiny of the blood film showed the presence of aggregates of amorphous pale staining materials in the thicker areas, which were barely discernible in the lighter-stained and better-spread areas. A ‘punch-hole’ appearance resulted when the red cells were overlaid with such materials (right panel). A review of the clinical history showed that the patient was a chronic hepatitis C carrier and had recently developed cryoglobulinaemia. The cryoglobulin level was 10·1 g/l. The blood sample was then warmed to 37°C and tested again; the thrombocytopenia was confirmed by the automated blood cell analyzer. Blood film examination showed normalization of the red cell morphology and disappearance of the amorphous materials, confirming that the amorphous materials were cryoglobulin.