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A 65-year-old man presents with a 1-month history of lower back pain, which began after he strained his back stacking fire wood. Despite rest and aspirin therapy it has not improved. He has not had similar back pain in the past and has been in good health. There are no neurological signs or symptoms on examination and he has no other complaints except possibly increased fatigability, which he attributed to his age. The remainder of his examination is normal with the exception of some conjunctival pallor.

CBC: Hematocrit/hemoglobin - 31%/10.1 gm/dL

MCV - 90 fL  MCH - 32 pg  MCHC - 31 g/dL

WBC - 8,500/μL

Differential - normal

Platelet count - 230,000/μL



Normochromic, normocytic red blood cells with prominent rouleaux formation (stacking) and a vague bluish background on the slide.

  • What feature(s) of this case might distinguish it from a routine lower back pain evaluation?

  • What further evaluation is indicated?

Plasma cells are terminally differentiated cells of the B lymphocyte lineage. They are thought of as cellular factories whose entire energy and synthetic capacity is devoted to producing a single antibody protein. They are normally incapable of dividing and are thought to have a relatively short lifespan of perhaps several weeks. Plasma cells develop both in the lymph nodes, where they are found predominantly in the medullary cords, and in the marrow, although they represent a minority of cells in these tissues. They have a distinctive morphology and are easily identified in the marrow (Figure 26-1).


Plasma cell differentiation and morphology. Mature B lymphocytes express on their surface the antibody that serves as the receptor for specific antigen. When they encounter this antigen, they are stimulated to proliferate and differentiate, which leads to development of memory B cells and plasma cells. The plasma cell is highly specialized to produce and secrete large amounts of the same antibody.

Plasma cell disorders, sometimes referred to as plasma cell dyscrasias, encompass several entities including monoclonal gammopathy of unknown significance (MGUS), Waldenström macroglobulinemia (WM), amyloidosis, and multiple myeloma (MM). The most common malignancy involving plasma cells is multiple myeloma, a multifaceted disease in which malignant plasma cells develop in bone marrow where they induce osteolytic lesions and produce monoclonal immunoglobulin components with humoral blood and urine repercussions.


After stimulation by specific antigen, the germinal center B cells differentiate to generate long-lived memory B cells on the one hand and plasma cells on the other (see Chapter 20). After then moving to the bone marrow, the plasma cell stops proliferating and manufactures large amounts (1 ng or more per cell per day) of the same antibody that was initially displayed on the surface of the B cell. The normal ...

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