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We read with much interest the 2019 classification criteria for IgG4-related disease by the American College of Rheumatology and the European League Against Rheumatism.1
This new classification driven by scientific evidence and research provides a substantial amount of new information, which will considerably improve the identification and management of patients with IgG4-related disease.
Despite the fact that radiology is integrated into the diagnostic criteria, only CT and/or positron emission tomography-CT are mentioned. We humbly suggest that the use of ultrasonography and/or MRI is missing. MRI is considered to be a relevant tool for diagnosing IgG4-related disease in the majority of organs included in the entry criteria such as the pancreas, bile ducts, orbits, lacrimal glands, major salivary glands, pachymeninges or thyroid gland.2 3 Its diagnostic accuracy is superior to that of CT and/or PET-CT for almost all organs, especially when imaging head and neck, orbital or brain IgG4-related disease. For example, detecting pachymeningitis with CT is challenging, whereas MRI is very sensitive.4 Moreover, MRI has proved to have high specificity to diagnose IgG4-related ophthalmic disease, in front of an enlargement of the infraorbital nerve.5 6 Advanced MRI techniques such as diffusion-weighted imaging, have excellent accuracy in distinguishing IgG4-ROD from lymphoma.7 Similarly, ultrasonography has been reported to easily detect changes in major salivary glands affected by IgG4-related diseases, even for inexperienced observers.8
One of the major points of the 2019 classification criteria for IgG4-related disease is that a positive diagnostic of IgG4-related disease can be achieved without invasive, tissue-based pathological confirmation. The update implies that non-invasive techniques such as imaging should have the best accuracy possible. CT and PET-CT have excellent sensitivity to detect lesions compatible with IgG4-related disease. However, MRI and ultrasonography have an even higher specificity in most organs. Moreover, MRI and ultrasonography are non-radiating techniques as opposed to CT and PET-CT.
Therefore, we believe that MRI and ultrasonography should be mentioned as first-line radiological examination choices in patients with a suspected diagnosis of IgG4-RD, especially for the head and neck and brain.
Patient consent for publication
Contributors AL and TS have written the Correspondence together.
Funding The authors have not declared a specific grant for this research from any funding agency in the public, commercial or not-for-profit sectors.
Competing interests None declared.
Patient and public involvement Patients and/or the public were not involved in the design, or conduct, or reporting, or dissemination plans of this research.
Provenance and peer review Not commissioned; internally peer reviewed.