Guy Katz, MD, MS

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.

"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.

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Malignancy, vasculitis, and sarcoidosis all overlap with IgG4-related disease. The panel reviews key mimics by organ and contrasts manifestations needing immediate treatment with those suited to active surveillance.

Understanding IgG4-RD: Definition, Epidemiology, and Multi-Organ Presentation

Welcome back to another HCPLive Peer Exchange series. In "Understanding IgG4-RD: Definition, Epidemiology, and Multi-Organ Presentation," moderator Emma Culver, BSc, MBChB, MRCP, DPhil is joined by Emanuel Della Torre, MD, PhD and Guy Katz, MD to open the series on IgG4-related disease.

Dr. Culver, a gastroenterologist and hepatologist in Oxford, begins by asking Dr. Della Torre to define the condition. He describes IgG4-related disease as a fibroinflammatory condition that can affect virtually any organ system. It typically presents as a triad of tumor-like mass-forming lesions, elevated serum IgG4, and characteristic pathology. The lesions resemble cancers but are not malignant. The disease takes its name from IgG4 elevation in serum and in tissue, where affected organs share a dense infiltrate of IgG4-expressing B-lineage cells.

On epidemiology, Dr. Della Torre notes that the disease remains rare, with a prevalence of no more than about 5 to 10 per 100,000 people. Men are affected more often than women, particularly in certain phenotypes. Women more often present with head and neck disease, while men more often have extracranial disease. As clinicians grow better at recognizing it, he predicts that IgG4-related disease may not be considered rare within a few years.

Dr. Katz explains why the disease is such a diagnostic challenge. In the head and neck, lacrimal, parotid, and submandibular glands may enlarge, sometimes with dry eyes or dry mouth. Often, however, the swelling is painless, symmetric, and asymptomatic. Autoimmune pancreatitis and sclerosing cholangitis are vital to recognize because of their high propensity for damage. The lungs, kidneys, prostate, retroperitoneum, and aorta can also be involved, as can the orbits, meninges, and thyroid.

In his experience, most patients have multi-organ disease, a pattern seen in cohorts worldwide. Single-organ disease is more typical of fibrotic manifestations such as retroperitoneal fibrosis, pachymeningitis, Riedel thyroiditis, and sclerosing mesenteritis. Inflammatory presentations, such as salivary gland disease, can occasionally occur alone. Still, most patients develop multi-organ involvement, if not at presentation, then during follow-up.

"IgG4-RD Mimics and the Manifestations That Require Urgent Treatment,"

 features the panel separating IgG4-related disease from its many look-alikes and identifying which organ involvement cannot wait.

IgG4-related disease can involve almost any organ and often begins without symptoms. The panel defines the condition, outlines who it affects, and describes the many ways it presents.

Guy Katz, MD, MS

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