The abnormality chosen is:
LEUKOPENIA, a white blood cell count less than 4000 cells/microL. This is most commonly a reflection of a diminished number of neutrophils (neutropenia); however, a reduction in the number of lymphocytes or monocytes may also be responsible. There are no directly related symptoms associated with leukopenia. If symptoms are present, they are usually related to the underlying disease state or process that caused the reduction in the white blood cell count. The most common complication is infection, which may present as fever, sepsis, or painful mucosal ulcers of the mouth or perirectal areas. Causes include marrow failure (secondary to medication, infection, aplastic anemia, or malignancy), vitamin deficiencies (B12 and folate), benign familial conditions, hypersplenism (especially when associated with concomitant thrombocytopenia), copper deficiency/zinc toxicity, and immunosuppressive states (HIV infection, Parvovirus B19). Associated splenomegaly may be secondary to underlying lymphoma or hepatic cirrhosis. Felty syndrome (rheumatoid arthritis, splenomegaly, and neutropenia) is a potential etiology in appropriate patients.
NEUTROPENIA is a reduction in the number of circulating neutrophils and may be classified on the basis of the absolute neutrophil count 
as mild (1000-2000 cells/microL), moderate (500-1000 cells/microL) or severe (<500 cells/microL). Blacks and Yemenite Jews have a lower normal limit than other races and this should be taken into consideration when evaluating individual patients. When severe neutropenia occurs acutely, it represents a life-threatening situation, and precautions to guard against infection should be employed. The various etiologies of neutropenia may be broadly classified as secondary to impaired cell production, increased margination with redistribution of neutrophils from the blood into the lymphoid tissues or accelerated neutrophil utilization/turnover. Drug-induced bone marrow impairment is a common cause of neutropenia. The bone marrow may also be suppressed by autoantibodies or T lymphocytes. This immune mediated impairment is more common is persons afflicted with rheumatic or autoimmune diseases. Pseudoneutropenia refers to an increase in marginated neutrophils with concomitant reduction in circulating neutrophils. This phenomenon usually occurs as the result of systemic infections and resolves with appropriate treatment of the infection. Hypersplenism may also result in neutropenia and should always be considered in the differential diagnosis when there is concomitant thrombocytopenia.
An appropriate initial work-up for neutropenia without an identifiable cause
after medication review, peripheral blood smear evaluation, and history/physical
exam includes lymphocyte immunophenotyping by flow cytometry and T-cell receptor gene rearrangement
on a peripheral blood sample studies to
evaluate for large granular lymphocyte leukemia, and antineutrophil antibody
testing to exclude immune neutropenia. Copper deficiency (malabsorption,
prolonged parenteral nutrition, post-gastrectomy, premature and malnourished
infants, copper chelator usage, zinc toxicity) is a cause of neutropenia with
concomitant anemia so patients should undergo testing
for serum copper and zinc levels in appropriate cases. When no etiology
can be identified after the above work-up, consultation with a hematologist and
consideration for bone marrow biopsy may be appropriate as
myelodysplastic syndromes may
present with an isolated cytopenia. Fever in a patient with
severe neutropenia is an emergency that requires an attempt to identify an
underlying infection (pan-cultures, chest radiograph, and possible spinal tap if
indicated) and then empiric broad spectrum antibiotics.
LYMPHOPENIA is a reduction in the absolute lymphocyte count 
to less than 1000 cells/microL. This abnormality is often secondary to stress, corticosteroids, alkylating agents or radiation.
Systemic lupus erythematosus often manifests with
lymphopenia. Less commonly, this abnormality occurs as the result of several rare immunologic diseases. There are no associated symptoms; however, this abnormality should be suspected in patients with recurrent viral, fungal, or parasitic infections.
MONOCYTOPENIA is associated with stress, acute infections, and hairy cell leukemia. Low eosinophils and basophils are not considered significant abnormalities as their concentrations in the peripheral blood are so low to begin with, and there is no significant adverse reactions associated with excessively low numbers of these cells.