AN UNUSUAL HISTIOCYTIC DISORDER : A CASE REPORT WITH EMPHASIS ON FLOW CYTOMETRIC STUDIES.

* M.Lima, ** A. Orfão, *** G. Ferreira, **** I. Freitas, ***** F. Silvestre, ** M.A.G. Marcos, * J. Coutinho, *** L.Bernardo, **** J. Vasconcelos, * M. Cunha, ***** J. Cabral, *** A.C. Fontes, **** M.A. Mendes, * B. Justiça.

* S.Clin. Hematology,
** S. Flow Cytometry, Clin and Universit. Hospital, Salamanca.
*** S. Medicin C,
**** S. Lab. Hematology,
***** S. Pathology, St. António's Hospital, Porto, Portugal.

Introduction: The histiocytic disorders include an heterogeneous group of diseases characterized by the proliferation of monocyte-macrophage or Langherans- dendritic cells. We report the clinical and laboratory findings of a patient presenting with an unusual histiocytic disorder.

Case report: 50-year-old male admitted for anemia and thrombocytopenia. Normal physical examination except for pallor. Hb 5.9 g/dl; Platelets 48x109/1; WBC 6.8x109/1: neutrophils 64%, lymphocytes 27%, monocytes 9%. LDH 744 U/1. Other biochemical tests: normal. Morphocytochemical findings: The BM aspirate showed 24% of pleomorphic blast cells, hemophagocytic features being occasionally observed. Most blasts were positive for acid phosphatase and some were positive for non-specific- esterases. Myeloperoxidase and Sudan-Black were negative. Flow Cytometric findings: Blasts had the following immunophenotype : CD4(+,dull), CD11a(+,dull), CD11c (+/-), CD13 (+/-), CD13cyt (+),CD15(+, dull), CD16a(+,dull), CD29(+), CD33(+,dull), CD35(++), CD36(-/+), CD38(++), CD42b (+), CD45(+,dull), CD45RA(+,dull), CD54(+), CD68 (cyt)(+), CD71(+,dull), CD117(+). Other cell markers including CD2, CD3, CD3(cyt), CD5, CD7, CD8, CD10, CD11b, CD14, CD19, CD20, CD22, CD22(cyt), CD34, CD41a, CD45RO, CD56, CD61, CDw65, BB4, GlycoA, HLA-Dr, chains(cyt), MPO(cyt) TCR and TCR(cyt) were negative.

Histopathological findings: BM biopsy showed an hypercellular BM, with moderate reticulin fibrosis, plaint of large cells with an abundant cytoplasm and an excentric nucleous with one or more shaped nucleoli. These cells were positive for LCA, lysozyme and CD68 and negative for lymphoid- associated markers.

Genetic findings: BM karyotype was normal. Other features: Putative causes for the histiocytic proliferation, either neoplastic, infeccious or toxic, were exaustively excluded. Chemotherapy was not performed. The patient became blood transfusion dependent.

Comments: In view of the atypical features, the diagnosis required a multidisciplinar approach. Flow cytometric studies were of great help, allowing an accurate characterization of the blast cells. Although we have no clear evidence for clonality, our results point to a primary histiocytic disorder of the bone marrow.