Long-Term Monitoring in IgG4-RD: Imaging, Serology, and Visit Frequency

This episode, "Long-Term Monitoring in IgG4-RD: Imaging, Serology, and Visit Frequency," features Dr. Katz walking through a practical surveillance framework.

Dr. Katz discusses monitoring with patients from their first visit. Because the disease is chronic and relapsing, and rare non-relapsers cannot be identified, everyone needs monitoring. His approach depends on how the disease manifests. Some patients have purely radiologic disease, with no symptoms and normal serum IgG4. Isolated retroperitoneal fibrosis is the typical example. After severe disease with hydronephrosis and ureteral obstruction, he obtains abdominal CT about every 3 months for the first year. He then extends imaging to every 6 months and later yearly. In milder disease, he images every 6 months for a year, then yearly, and spaces scans further after prolonged stability.

Most patients have elevated serum IgG4 at baseline, often with high C-reactive protein, high IgE, hypocomplementemia, or eosinophilia. Of these, serum IgG4 correlates best with disease activity. A falling level makes relapse unlikely, and a stable level usually does too. A rising level suggests current or impending relapse. However, he cautions that this pattern is far from definitive, and many patients do not follow it.

He checks laboratory tests every 2 to 4 months. He uses 2-month intervals in severe disease or after a prior relapse. He uses 4-month intervals in milder, head and neck–limited disease, where detecting relapse immediately is less critical.

Dr. Katz currently monitors every patient indefinitely. Clinicians do not know what long-term remission off treatment means. He has no patients he is confident will never relapse. He prefers not to return patients to primary care, because monitoring this rare disease falls outside most primary care practices. Some stable patients are seen yearly or every 18 to 24 months, with laboratory tests in between.

He finds that patients understand surveillance intuitively once he explains organ-specific damage. Examples include dry mouth, irreversible airway changes, and kidney, pancreatic, or retroperitoneal injury.

Our next episode, "Defining Treatment Success, Switching Therapy, and Managing IgG4-RD Complications," turns to what success looks like for individual patients and how the team manages complications over time.