Neutropenia

Neutropenia is defined as a decrease in the absolute neutrophil count (ANC). The ANC is calculated by multiplying the total WBC count by the percentage of segmented neutrophils and bands. Neutropenia is defined as an ANC of less than 1000/mm3 in infants between 2 weeks and 1 year of age and less than 1500/mm3 beyond 1 year of age.

Severity and duration of neutropenia correlate with susceptibility to developing various types of bacterial infections. Severity of neutropenia is graded according to ANC as follows:

Severe neutropenia: ANC less than 500/mm3 Moderate neutropenia: ANC 500-1000/mm3 Mild neutropenia: ANC 1000-1500/mm3.

Neutropenic patients are usually infected with their own endogenous bacterial flora that reside in the mouth, oropharynx, gastrointestinal tract, and skin. For this reason, the frequency of gram-negative bacterial infections and Staphylococcus aureus infections is high in these patients. Neutropenia alone does not, per se, predispose them to parasitic, viral, or fungal infections.

Benign ethnic neutropenia is observed in a variety of populations including Africans, West Indians, Yemenite and Ethiopian Jews, Beduin Arabs, and Jordanians. In these groups an ANC as low as 1000/mm3 may be considered normal.

Clinical Features

Severe neutropenia has the following common clinical manifestations:

1. High fever, chills, severe prostration, and irritability

2. Extensive necrotic and ulcerative lesions: oropharyngeal and nasal tissues, skin, gastrointestinal (GI) tract, vagina, and uterus

3. Gram-negative septicemia.

The risk of infection is inversely proportional to the ANC. When the ANC falls below 1000/mm3, stomatitis, gingivitis, and cellulitis dominate the clinical picture. More severe infections occur when the ANC is below 500/mm3 with perirectal abscesses, pneumonia, and sepsis being common.

Granulocyte colony-stimulating factor (G-CSF) produces a sustained neutrophil recovery in patients with severe chronic neutropenia, reduces the incidence and severity of infection, and improves the quality of life. The drug is tolerated well and adverse effects are transient and mild. Neutropenia can be transient (<8 weeks) or chronic (>8 weeks). Table 9-6 lists the causes of neutropenia, and Figure 9-1 shows an approach to the diagnosis of neutropenia.

Neutropenia (previously normal neutrophil count)

No (congenital)

Underlying disease / \

Absent Immune Drug-induced Idiopathic

Abnormal

Present Leukemia Metastic disease Viral/bacterial infection Splenic sequestration

Normal

Shwachman-Diamond syndrome Cartilage-Hair syndrome Dyskeratosis congenita Fanconi anemia Osteopetrosis

Repeated infections Absent

Chronic benign neutropenia Familial benign neutropenia

Present

Infantile agranulocytosis (Kostmann disease) Reticular dysgenesis T- and B-cell abnormalities Severe congenital neutropenia Cyclic neutropenia

Fig. 9-1. Approach to diagnosis of neutropenia. (From Roskos RR, Boxer LA. Clinical disorders of neutropenia. Pediatr Rev 1991;12:208-12, with permission.)

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