Leukopenia (Low White Blood Cell Count): Signs, Causes, and Medical Workup

Leukopenia = white blood cell (WBC) count below the normal range (<4,000/µL). The most common form is neutropenia (low neutrophils), which directly increases infection risk.

Signs and Symptoms

• Frequent, prolonged, or unusual infections
• Fever, chills, night sweats
• Fatigue, weakness, malaise
• Slow-healing wounds, oral ulcers, gingivitis
• Easy bruising or bleeding (if platelets also low)
• Weight loss, abdominal pain, diarrhea

Common Causes

• Viral infections: HIV, hepatitis B/C, EBV, CMV, parvovirus.
• Autoimmune disorders: Lupus, rheumatoid arthritis, Felty's syndrome.
• Medications: Chemotherapy, antibiotics (TMP-SMX, penicillin), anticonvulsants, antipsychotics, clozapine.
• Bone marrow disorders: Aplastic anemia, MDS, leukemia, myelofibrosis.
• Nutritional deficiencies: B12, folate, copper.
• Splenomegaly: Sequestration (hypersplenism).

Medical Evaluation

CBC with differential, peripheral blood smear, medication review, and targeted workup based on clinical context (viral serologies, autoantibodies, bone marrow biopsy if indicated). Treat the underlying cause; monitor closely for infection.