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INTRODUCTION

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CASE HISTORY • Part 1

A 23-year-old woman presents with recurrent episodes of sinusitis, a well-documented pneumococcal pneumonia at age 17, and a chronic productive cough for over a year; the latter has not responded to several courses of antibiotics. She has lost 10 lbs over the last 6 months and feels chronically ill. Her sexual history includes unprotected sex with at least 5 different males over the last 4 years.

On examination, she is afebrile with normal vital signs but appears poorly nourished and chronically ill. She has palpable, slightly enlarged, non-tender cervical lymph nodes and a palpable spleen without hepatomegaly. Chest examination is remarkable for prominent rhonchi and crackles throughout the lower lung fields, without signs of pleural fluid or consolidation. Fingers appear to be slightly clubbed. A routine complete blood count (CBC) is drawn and chest film obtained:

CBC: Hematocrit/hemoglobin - 33%/11 g/dL

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MCV - 93 fL MCH - 31 pg MCHC - 33 g/dL
WBC count - 10,900/μL
Differential:

Neutrophils - 7,500/μL

Lymphocytes - 2,450/μL

Monocytes - 850/μL

Eosinophils - 100/μL

Platelets - 35,000/μL

Chest film: Nonspecific scarring in both lower lobes. No evidence of consolidation or pleural fluid.

Questions
  • Do the history and physical examination suggest a diagnosis?

  • What abnormalities are apparent from the CBC?

  • What additional workup is in order?

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The immune system, consisting of both the adaptive (T and B cells) and the innate (natural killer [NK] cells, macrophages, and myeloid effector cells) components as described in Chapter 20, is carefully balanced and interactive; thus, immune dysfunction of any kind is frequently associated with the combination of impaired defense against pathogens, autoimmunity, and increased risk of malignancy.

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Constitutional or primary immune deficencies are relatively rare disorders, affecting mainly young infants. Acquired immune deficiency has become a more dominant issue with the advent of the human immunodeficiency virus (HIV) epidemic. The diagnosis and treatment of HIV and its associated life–threatening complications (AIDS) has become a major occupation for many medical subspecialties, including hematology. One of the early clues to an acquired immunodeficiency state is the development of absolute lymphopenia. At the same time, patients may manifest profound immune defects with normal or even elevated lymphocyte counts.

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NORMAL LYMPHOCYTE KINETICS

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The pathways of lymphocyte development are described in detail in Chapter 20. Lymphocytes arise from progenitors in the marrow and develop in the lymphoid organs including, for T cells, the thymus and lymph nodes, and for B cells, the marrow and lymph nodes. Circulating lymphocytes in blood are not representative of all lymphocytes, but rather are particular subsets that circulate for specific reasons (Table 21-1).

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TABLE 21-1The normal distribution of lymphocyte subsets in blood

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