IgG4-RD Mimics and the Manifestations That Require Urgent Treatment

This episode, "IgG4-RD Mimics and the Manifestations That Require Urgent Treatment," features the panel examining how organ location shapes both the differential diagnosis and the urgency of therapy.

Dr. Katz notes that the list of conditions mimicking IgG4-related disease is "about a mile long." The most relevant mimics depend on the organ involved. In the head and neck, he considers Sjögren's disease and sarcoidosis, which commonly involve the glands. Lymphoma is another important cause of glandular enlargement. In the lungs, antineutrophil cytoplasmic antibody–associated vasculitis and sarcoidosis are leading mimics. In the retroperitoneum, Erdheim-Chester disease and other malignant conditions frequently cause confusion.

Because IgG4-related disease forms masses, Dr. Katz stresses that malignancy belongs on the differential for nearly every presentation. Dr. Culver then asks which manifestations demand immediate treatment. Dr. Katz considers internal organ involvement the most urgent overall. Outside the internal organs, vision-threatening orbital inflammation or orbital myositis causing diplopia can be urgent. Pachymeningitis with cranial nerve deficits also warrants prompt action. However, orbital and meningeal disease is often chronic and slowly progressive rather than urgent by definition.

Autoimmune pancreatitis is one manifestation Dr. Katz tries to treat urgently, because the pancreas tolerates inflammation poorly. Patients have a high propensity for exocrine and endocrine damage. Retroperitoneal fibrosis that is obstructing the ureters, or appears about to, also needs immediate treatment. Aortitis and coronary arteritis or periarteritis can cause serious complications if untreated, so he regards them as relatively urgent too.

Dr. Della Torre describes himself as aggressive, treating nearly every manifestation at presentation. He reasons that even clinically silent disease may rapidly lead to organ damage. He considers watchful waiting when disease is limited to lymph nodes without parenchymal involvement. He also hesitates when imaging is discordant, such as PET uptake without morphologic change on CT or MRI. In those cases, he uses active surveillance, shortening the intervals between visits and examinations to anticipate clinical disease.

Our next episode, "Diagnosing IgG4-RD: Why Classification Criteria Are Not Diagnostic Criteria," turns to how clinicians confirm the diagnosis and where formal classification criteria help or mislead.