Differential Diagnosis for Leukopenia and ANA Positivity
Single Most Likely Diagnosis
- Systemic Lupus Erythematosus (SLE): This is the most likely diagnosis due to the combination of leukopenia and ANA positivity, as SLE is a common cause of both findings. SLE is a chronic autoimmune disease that can affect multiple organ systems and is characterized by a positive ANA test in the majority of cases.
Other Likely Diagnoses
- Rheumatoid Arthritis (RA): While RA is more commonly associated with neutrophilia, some patients can present with leukopenia, and ANA positivity can be seen in a subset of patients, particularly those with more systemic symptoms.
- Sjögren's Syndrome: This autoimmune disorder can present with leukopenia and is often associated with ANA positivity. It primarily affects the exocrine glands, but systemic manifestations can occur.
- Mixed Connective Tissue Disease (MCTD): MCTD overlaps with SLE, RA, and scleroderma, and patients often have a positive ANA test. Leukopenia can be a feature of MCTD, making it a plausible diagnosis.
Do Not Miss Diagnoses
- Felty's Syndrome: A complication of long-standing RA, characterized by rheumatoid arthritis, splenomegaly, and neutropenia (a form of leukopenia). Although less common, missing this diagnosis could lead to significant morbidity due to increased risk of infections.
- Drug-Induced Lupus: Certain medications can induce a lupus-like syndrome, which includes leukopenia and ANA positivity. This diagnosis is critical to consider because withdrawal of the offending drug can lead to resolution of symptoms.
- HIV Infection: HIV can cause leukopenia and is associated with a variety of autoimmune phenomena, including ANA positivity. Missing this diagnosis could have severe consequences due to the importance of early antiretroviral therapy.
Rare Diagnoses
- Autoimmune Lymphoproliferative Syndrome (ALPS): A rare disorder characterized by an abnormal immune response, leading to lymphadenopathy, splenomegaly, and cytopenias, including leukopenia. ANA positivity can be seen, but it is less common.
- Primary Antiphospholipid Syndrome: Although primarily known for its association with thrombosis, some patients can present with cytopenias, including leukopenia, and may have a positive ANA test.