A 45-year-old patient presents with symptoms suggestive of an autoimmune disorder. Serological tests reveal the following results: positive anti-nuclear antibody (ANA) with a speckled pattern, positive anti-Smith (anti-Sm) antibodies, and negative anti-double-stranded DNA (anti-dsDNA) antibodies.
What is the most likely diagnosis, and how do these serological findings guide the diagnosis
Based on the serological test results, the most likely diagnosis is Systemic Lupus Erythematosus (SLE).
Here’s how the serological findings guide the diagnosis:
1. Positive anti-nuclear antibody (ANA) with a speckled pattern: ANA is a sensitive marker for SLE, and a speckled pattern is commonly seen in SLE patients.
2. Positive anti-Smith (anti-Sm) antibodies: Anti-Sm is a specific marker for SLE, and its presence is a strong indicator of the disease.
3. Negative anti-double-stranded DNA (anti-dsDNA) antibodies: While anti-dsDNA is a common antibody in SLE, its absence doesn’t rule out the diagnosis. Some SLE patients may not have anti-dsDNA antibodies, especially early in the disease course.