Differential Diagnosis for Isolated Lymphocytosis
Single Most Likely Diagnosis
- Viral Infection: This is the most common cause of isolated lymphocytosis, especially in a young adult. Viral infections such as infectious mononucleosis (caused by Epstein-Barr virus), cytomegalovirus, and influenza can lead to an increase in lymphocyte count.
Other Likely Diagnoses
- Stress or Anxiety: Stress and anxiety can cause a reactive lymphocytosis, although this is usually mild.
- Hypothyroidism: Some cases of hypothyroidism can present with lymphocytosis, although this is not a common finding.
- Chronic Fatigue Syndrome: This condition can also be associated with lymphocytosis, although the diagnosis is often based on clinical criteria.
Do Not Miss Diagnoses
- Lymphoma or Leukemia: Although less likely, it is crucial to rule out lymphoma or leukemia, as these conditions can be life-threatening if not diagnosed and treated promptly.
- HIV Infection: HIV can cause an increase in lymphocyte count, especially in the early stages of infection.
- Tuberculosis: In some cases, tuberculosis can cause lymphocytosis, especially if the infection is disseminated.
Rare Diagnoses
- Lymphocytic Leukocytosis with Vacuolated Lymphocytes (LLVL): A rare condition characterized by an increase in lymphocyte count with vacuolated lymphocytes.
- Pseudolymphoma: A rare condition that can mimic lymphoma but is often benign.
- Castleman Disease: A rare lymphoproliferative disorder that can cause lymphocytosis.
- Autoimmune Lymphoproliferative Syndrome (ALPS): A rare genetic disorder that can cause lymphocytosis and other immune system abnormalities.