Skip to Main Content

++

INTRODUCTION

++

  • Monocytes in the blood are in transit. They function in the tissues, where they mature into macrophages and participate in:

    — Inflammation, including granulomatous reactions, atheroma formation, and tissue repair

    — Immunologic reactions, including delayed hypersensitivity

    — Reactions to neoplasia and allografts

  • The need for macrophages in tissues also can be met by local proliferation of macrophages, not requiring increased transit of blood monocytes.

  • Ninety percent of blood monocytes intensely express CD14 (lipopolysaccharide receptor) but not CD16 (Fc receptor) and 10% have weak expression of CD14 and strongly express CD16.

  • Older persons have a striking decrease in the proportion of CD14++CD16– to CD14+CD16+ monocytes compared with younger persons.

  • Disorders rarely produce abnormalities of monocytes alone in the absence of other blood cell abnormalities.

++

NORMAL BLOOD MONOCYTE CONCENTRATION

++

  • The monocyte count averages 1.0 × 109/L in neonatal life, gradually decreasing to a mean of 0.4 × 109/L in adult life.

  • Monocytosis (in adults) is greater than 0.8 × 109/L.

  • Monocytopenia is less than 0.2 × 109/L.

++

HEMATOLOGIC DISORDERS ASSOCIATED WITH MONOCYTOSIS

++ ++
Table Graphic Jump Location
TABLE 35–1DISORDERS ASSOCIATED WITH MONOCYTOSIS
++

Neoplastic or Clonal Monocytic Proliferations

++

  • Oligoblastic myelogenous leukemia (refractory leukemia with excess blasts or myelodysplastic syndrome)

  • Acute myelogenous leukemia (myelomonocytic or monocytic types)

  • Chronic myelomonocytic leukemia

  • Juvenile myelomonocytic leukemia

  • Unusual type of BCR-ABL (p190)-positive chronic myelogenous leukemia with monocytosis

++

Reactive (Nonclonal) Monocytic Proliferations

++

  • Neutropenic states: cyclic neutropenia; chronic granulocytopenia of childhood; familial benign neutropenia; infantile genetic agranulocytosis; chronic hypoplastic neutropenia

  • Drug-induced agranulocytosis (transient monocytosis, especially in the recovery phase)

  • Chlorpromazine toxicity, monocytosis preceding the agranulocytosis

  • Lymphoma

  • Hodgkin lymphoma

  • Postsplenectomy state

  • Myeloma

++

INFLAMMATORY AND IMMUNE DISORDERS ASSOCIATED WITH MONOCYTOSIS

++

Pop-up div Successfully Displayed

This div only appears when the trigger link is hovered over. Otherwise it is hidden from view.