Differential Diagnosis for 15-year-old Male Patient

The patient presents with leukopenia (total leukocytes of 3990), a relatively low neutrophil count (45% of total leukocytes), and a normal red cell distribution width (RDW of 15.1). The patient's symptoms include poor sleep and general feelings of malaise. Based on these findings, the differential diagnosis can be categorized as follows:

• Single Most Likely Diagnosis
  • Viral Infection: Many viral infections can cause leukopenia, particularly a decrease in neutrophils, and are often accompanied by non-specific symptoms such as malaise and sleep disturbances. The patient's age and presentation make this a plausible explanation.
• Other Likely Diagnoses
  • Anemia of Chronic Disease: Although the RDW is within the normal range, which might not strongly support iron deficiency anemia, anemia of chronic disease could still be considered, especially if there are underlying chronic conditions not immediately apparent. The malaise could be a symptom of anemia.
  • Hypersplenism: This condition can lead to leukopenia due to splenic sequestration of white blood cells. However, it would typically be associated with other signs such as splenomegaly and possibly anemia or thrombocytopenia.
  • Medication-induced Leukopenia: Certain medications can cause a decrease in white blood cell count. If the patient is on any medications, this could be a consideration.
• Do Not Miss Diagnoses
  • Aplastic Anemia: Although rare, aplastic anemia is a serious condition that can present with leukopenia and symptoms like malaise due to anemia. It requires prompt diagnosis and treatment.
  • Leukemia or Lymphoma: These malignancies can cause abnormalities in blood cell counts, including leukopenia. Early detection is crucial for effective treatment.
  • HIV Infection: HIV can cause a variety of hematologic abnormalities, including leukopenia. Given the potential severity of the disease, it's essential not to miss this diagnosis.
• Rare Diagnoses
  • Congenital Neutropenias: These are rare conditions present from birth that affect the production of neutrophils. They could be considered if the patient's history and other findings support a long-standing condition.
  • Cyclic Neutropenia: A rare condition characterized by periodic decreases in neutrophil count, which could explain the patient's symptoms if they are cyclic in nature.
  • Autoimmune Neutropenia: An immune-mediated destruction of neutrophils, which is rare and might be considered if other autoimmune conditions are present or suspected.

Each of these diagnoses requires careful consideration of the patient's full clinical picture, including detailed history, physical examination, and potentially additional laboratory tests to confirm or rule out the conditions listed.