Can mycophenolate (Cellcept) affect the lip biopsy focus score in Sjögren's syndrome?

Impact of Mycophenolate on Lip Biopsy Focus Score in Sjögren's Syndrome

Yes, mycophenolate (CellCept) can affect the lip biopsy focus score in Sjögren's syndrome by potentially reducing the number and size of lymphocytic foci, which may lead to false-negative results. 1

Mechanism and Evidence

Mycophenolate, as an immunosuppressive medication, works by:

• Inhibiting lymphocyte proliferation
• Reducing inflammatory cell infiltration in tissues
• Potentially decreasing the number and size of lymphocytic foci in salivary glands

This effect is similar to what has been documented with other immunosuppressive medications like prednisone, which can reduce focus scores below diagnostic thresholds 1.

Clinical Implications

Diagnostic Accuracy Concerns

• Focus score calculation relies on counting aggregates of ≥50 mononuclear cells per 4 mm² of glandular tissue
• A focus score ≥1 is considered diagnostic for Sjögren's syndrome 1
• Immunosuppressive medications taken for >6 weeks prior to biopsy may significantly affect results 2

Recommendations for Biopsy Timing

• If possible, mycophenolate should be discontinued at least 6 weeks prior to planned lip biopsy
• For patients who cannot discontinue mycophenolate due to other medical conditions:
  • Document dosage and duration of treatment when submitting the biopsy
  • Place greater emphasis on other diagnostic criteria 1

Alternative Diagnostic Approaches

When a patient is on mycophenolate and cannot discontinue:

1. Serological markers: Anti-SSA/Ro and anti-SSB/La antibodies
2. Objective measures: Ocular and oral dryness tests
3. Clinical symptoms: Documented sicca symptoms

Patients with both sicca symptoms and positive serology have a higher likelihood (75%) of positive biopsy results even without medication interference 2.

Biopsy Considerations

When biopsy is necessary despite medication use:

• Obtain sufficient tissue (minimum of four labial salivary glands) to ensure adequate sampling 1
• Use standardized focus score calculation methods to minimize misinterpretation 3
• Consider that pathologic misinterpretation occurs in approximately 10% of specimens, with incorrect application of grading systems in up to 45% of cases 4

Pitfalls to Avoid

1. Ignoring medication history: Always document immunosuppressive medication use when interpreting results
2. Relying solely on biopsy: In patients on immunosuppressants, use multiple diagnostic criteria
3. Inadequate sampling: Insufficient glandular tissue can lead to false negatives
4. Inconsistent scoring: Ensure standardized application of focus score calculation 3

Remember that while lip biopsy is a valuable diagnostic tool with a high specificity when properly performed, its results must be interpreted in the context of the patient's medication history, particularly when immunosuppressive agents like mycophenolate are involved.