Are there concerns with a 62-year-old male patient with MOGAD, psoriatic arthritis, and celiac disease, on 3g sulfasalazine (sulfasalazine) and 4mg prednisone (prednisone), with elevated RDW-SD and low MCH?

Assessment of Laboratory Values in a 62-Year-Old Male with MOGAD, Psoriatic Arthritis, and Celiac Disease on Sulfasalazine and Prednisone

The elevated RDW-SD of 46.9 is concerning and requires monitoring of complete blood counts, as sulfasalazine can cause hematologic abnormalities including blood dyscrasias that may present with anisocytosis.

Laboratory Values Analysis

The patient presents with the following laboratory values:

• RDW-SD: 46.9 (elevated)
• Mean Corpuscular Hemoglobin (MCH): 32.6 (within normal range)
• Red Blood Cell Count: 4.3 (within normal range)

Interpretation of Values:

• The elevated RDW-SD indicates increased red blood cell size variability (anisocytosis)
• Normal MCH suggests adequate hemoglobin content in red blood cells
• Normal RBC count indicates adequate red blood cell production

Medication Considerations

Sulfasalazine (3g daily)

• Sulfasalazine carries FDA warnings for potential hematologic abnormalities including agranulocytosis, aplastic anemia, and other blood dyscrasias 1
• Complete blood counts should be monitored frequently in patients receiving sulfasalazine 1
• Guidelines recommend monitoring CBC, liver function tests, and renal function within the first 1-2 months of usage and every 3-4 months thereafter 2
• The dose should be decreased or held if clinically relevant abnormalities in blood counts are found 2

Prednisone (4mg)

• Low-dose prednisone is commonly used in psoriatic arthritis (up to 30% of patients in registry data) 2
• This relatively low dose is less likely to contribute to hematologic abnormalities

Risk Assessment

The patient has multiple factors that increase monitoring importance:

1. Multiple autoimmune conditions: MOGAD (Myelin Oligodendrocyte Glycoprotein Antibody-Associated Disease), psoriatic arthritis, and celiac disease
2. High-dose sulfasalazine: 3g daily is at the upper end of the typical dosing range for psoriatic arthritis 2
3. Elevated RDW-SD: May be an early indicator of medication-related hematologic effects

Recommended Approach

1. Obtain comprehensive CBC with differential and peripheral smear

   • To evaluate for other hematologic abnormalities not captured in the current results
   • To assess for neutropenia, thrombocytopenia, or other cell line abnormalities

2. Add liver and renal function tests

   • Sulfasalazine can cause hepatotoxicity and renal damage 1
   • Guidelines recommend monitoring these parameters alongside CBC 2

3. Consider folate supplementation

   • Sulfasalazine interferes with folic acid metabolism 3
   • Folate/folinic acid supplementation is strongly recommended with similar medications like methotrexate 2

4. Evaluate celiac disease control

   • Poor celiac disease control can contribute to anemia and altered RDW
   • Ensure adequate adherence to gluten-free diet

5. Monitor for clinical symptoms

   • Pay attention to signs such as fatigue, pallor, bruising, bleeding, or infections
   • The presence of clinical signs like sore throat, fever, pallor, purpura, or jaundice may indicate serious blood disorders 1

Follow-up Plan

• Repeat CBC, liver function, and renal function tests within 2-4 weeks
• If RDW-SD continues to increase or other abnormalities develop, consider:
  • Reducing sulfasalazine dose
  • Temporary discontinuation of sulfasalazine
  • Alternative DMARD therapy

Conclusion

While the isolated elevated RDW-SD with normal MCH and RBC count is not immediately alarming, it warrants closer monitoring given the patient's medication regimen and multiple autoimmune conditions. Sulfasalazine's known potential for hematologic toxicity requires vigilance and appropriate laboratory monitoring to prevent serious adverse events.