Bone Marrow Reticulin in Patients with Immune Thrombocytopenic Purpura.

Immune thrombocytopenic purpura (ITP) is an uncommon disorder, and research that characterizes the bone marrow stroma in ITP patients is lacking. It is known that megakaryocytes are often increased in number in ITP patients. Megakaryocytes are associated with reticulin formation in other conditions, including malignant and nonmalignant diseases, such as systemic lupus erythematosus and other immune disorders. Our objective was to determine if the reactive megakaryocyte proliferations in ITP are associated with increased reticulin deposition. We identified 40 ITP patients from clinical records in a retrospective survey of bone marrow biopsy material. Patients were required to have had a diagnosis of ITP, a bone marrow biopsy with available tissue blocks, and a complete blood count at the time of the biopsy. Paraffin-embedded sections from the bone marrow biopsy specimens were stained for reticulin using standard silver-impregnation methods. Reticulin was quantified using the Bauermeister scale (0 = no reticulin fibers demonstrable; 1 = occasional fine individual fibers and foci of a fine fiber network; 2 = fine fiber network throughout most of the section but no coarse fibers; 3 = diffuse fiber network with scattered thick coarse fibers but no mature collagen; and 4 = diffuse often coarse fiber network with areas of collagen). In addition, bone marrow cellularity and megakaryocyte numbers were evaluated. Of the 40 patients, 13 (33%) were considered to have absent (grade 0) bone marrow reticulin, 1 (2%) had grade 0–1, 20 (50%) had grade 1, 5 (13%) had grade 1–2, and 1 (2%) had grade 2. Thus, reticulin was present in the bone marrow of approximately two-thirds of the patients, with 15% having greater than grade 1. Previous research on bone marrow reticulin in 100 hematologically normal subjects found that 27% had Bauermeister reticulin grade 1 and 4% had grade 2 (