Disorders of White Blood Cells

Published on 06/06/2015 by admin

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Last modified 06/06/2015

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51 Disorders of White Blood Cells

White blood cells (WBCs), or leukocytes, are an integral part of the host immune system. Their microscopic appearance after Wright-staining categorizes them as either granulocytes (neutrophils, eosinophils, and basophils) or agranulocytes (monocytes, macrophages, and lymphocytes). Each WBC has a specific function within the immune system (Figure 51-1).

A complete blood count (CBC) and manual differential notes the total number of WBCs per microliter of sample as well as the percentages of each subset of WBC. Absolute counts for each WBC are more clinically meaningful than percentages. Reference ranges for the WBC differential vary by age. In general, newborns have high total WBC counts (≤30,000/µL). At about 1 week of age, an infant’s total WBC decreases into the range of 5000 to 21,000/µL. Through the toddler and childhood years, the mean WBC count decreases slowly to an adult average of 7500/µL. Lymphocyte predominance is seen from 2 weeks to about 5 years of age. Then neutrophils are predominant, making up more than 50% of the differential. Monocytes, eosinophils, and basophils make up a very small percentage of the total WBC from the neonatal period through adulthood.

Clinical Presentation and Differential Diagnosis

Congenital Disorders of Neutrophils

Because neutrophils play a key role in host defense, the primary signs and symptoms of neutropenia are related to an increased susceptibility to infection, particularly bacterial and fungal. Children with chronic neutropenia can develop cellulitis, perirectal or other deep tissue abscesses, oral ulcers, periodontal disease, pneumonia, and septicemia. Endogenous Staphylococcus aureus or gram negative organisms are frequently isolated. Clinical signs of infection, such as erythema and warmth, may be diminished secondary to a decreased neutrophil response.

There are multiple congenital neutropenias that are being further categorized as knowledge of the genetic basis of disease improves (Tables 51-1 and 51-2). These congenital disorders are exceedingly rare.

Table 51-2 Additional Congenital Disorders Associated with Neutropenia

Disorder Clinical Manifestations
Cartilage-hair hypoplasia Short limbs, dwarfism, abnormally fine hair
Myelokathexis with dysmyelopoiesis Marrow retention of neutrophils, recurrent bronchopulmonary infections
Dyskeratosis congenita Bone marrow failure syndrome; dystrophic changes in nails, skin (hyperpigmentation), and mucous membranes (leukoplakia)
Fanconi anemia Bone marrow failure syndrome; GU and skeletal abnormalities, increased chromosome fragility
Organic acidemias (propionic, methylmalonic) Initially well at birth, then toxic encephalopathy
Osteopetrosis Defective bone turnover with resultant hematopoietic insufficiency and bone fragility
Reticular dysgenesis (congenital aleukocytosis) Absent WBC, hypogammaglobulinemia, thymic hypoplasia, severe infection and death in infancy
Immunodeficiencies (severe combined immunodeficiency, common variable immunodeficiency, hyper-IgM) Frequent infections, failure to thrive, hepatosplenomegaly
Glycogen storage disease type 1b (von Gierke disease) and other inborn errors of metabolism Neutropenia and functional neutrophil defect, hepatosplenomegaly

GU, genitourinary; WBC, white blood cell.