Key points

Introduction

Granulomatous inflammation is a unique form of chronic inflammation. Granulomas are distinct structures composed of epithelioid-shaped macrophages, multinucleated giant cells, lymphocytes, and fibroblasts. However, the clinical findings associated with granulomatous inflammation are usually variable and often indistinct. Granulomatous inflammation has a multifactorial cause and may arise as a reaction to environmental or genetic factors, infectious organisms, or it may be idiopathic, for which there is no known trigger. A typical differential diagnosis includes foreign-body reactions, infection, Crohn disease (CD), sarcoidosis, and orofacial granulomatosis (OFG). Less commonly, other systemic diseases may also be associated with granuloma formation.

Foreign substances are the most common source of localized granulomatous inflammation in the oral cavity. There are numerous endogenous and exogenous substances that may trigger foreign-body reactions. Relatively common endogenous sources include hair fibers, keratin aggregates, and lipids derived from cholesterol deposits and fat emboli. Exogenous materials may include an array of commonly used dental materials, retained sutures, and cosmetic filler substances, such as hyaluronic acid, which are used for labial and perilabial augmentation.

Foreign-body reactions are associated with nonspecific clinical findings. These findings may include nondescript masses, erythema, localized or generalized edema, pain, or ulceration. A tissue biopsy is typically warranted for diagnosis, and, in many cases, the foreign material is readily evident on microscopic examination. In general, the clinical manifestations subside after removal of the foreign substance in conjunction with topical or intralesional corticosteroid treatment.

The persistence of signs and symptoms may warrant additional clinical and laboratory testing to identify other possible sources of the inflammation. This situation is particularly true if the patient shows manifestations that are diffuse and cannot be readily explained by the presence of localized foreign material. The absence of identifiable foreign material does not preclude a clinical diagnosis of foreign-body reaction; a detailed history and evaluation may help increase the index of suspicion. However, unless the foreign substance is identified in microscopic sections, histologic evidence of granulomatous inflammation often presents a diagnostic dilemma for the clinician. With new insights into the pathogenesis of specific granulomatous diseases, and with the advent of high-throughput genetic screening and availability of next-generation biological therapies, clinicians now have several options at their disposal to help ensure accurate diagnosis and effective treatment. The discussion that ensues highlights some of the current knowledge about the more common granulomatous systemic diseases that may be encountered in clinical practice.