Clinical review: Riedel's thyroiditis: a clinical review.

CONTEXT: Riedel's thyroiditis is a rare inflammatory process involving the thyroid and surrounding cervical tissues and is associated with various forms of systemic fibrosis. Riedel's presentation is complex, including a thyroid mass associated with local symptoms, characteristic biochemical abnormalities such as hypocalcemia and hypothyroidism, as well as the involvement of a wide range of other organ systems. Diagnosis of Riedel's thyroiditis requires histopathological confirmation, but due to high complication rates, the role of surgical intervention is limited to airway decompression and diagnostic tissue retrieval. Unique among processes of the thyroid, Riedel's is commonly treated with long-term antiinflammatory medications to arrest progression and maintain a symptom-free course. Due to its rarity, Riedel's may not be immediately diagnosed, so clinicians benefit from recognizing the constellation of findings that should make prompt diagnosis possible.

EVIDENCE ACQUISITION: A review of print and electronic reviews was conducted. Source references were identified, and available literature was reviewed. A search of the PubMed database using the search term "Riedel's thyroiditis" was cross-referenced with associated clinical findings, systemic fibrosis diagnoses, and therapeutic search terms. Because most of the literature consisted of case reports and very small series, inclusion of identified articles was based on clinical descriptions of the subjects included and the criteria for diagnosis reported. More weight was attributed to series, using contemporary criteria for diagnosis. Case reports were included if the diagnosis was clear and clinical presentation was unique to illustrate the spectrum of disease.

EVIDENCE SYNTHESIS: Because the majority of therapeutic intervention data were based upon case reports and very small series, an evidence-based approach was problematic, but information is presented as objectively and with as much balance as the limited quality of the data allows.

CONCLUSIONS: Clinical awareness of the characteristic presentations of Riedel's thyroiditis should enhance our ability to make this diagnosis in a timely and focused manner. Recognition of certain clinical finding patterns will increase the likelihood of recognizing Riedel's thyroiditis promptly. Local restrictive or infiltrative symptoms out of proportion to a demonstrable mass or simultaneous biochemical deficiencies especially of calcium should lead the clinician to consider this diagnosis. Likewise in this setting, the surgeon alert to this possibility may minimize overly aggressive surgical intervention, thus avoiding complications. Once Riedel's thyroiditis is diagnosed, the application of antiinflammatory therapies may greatly enhance the clinical outcome. Understanding the pathophysiological relationship of this entity with other forms of systemic fibrosis and the role that IgG4 may play in this process should result in enhanced diagnostic and therapeutic tools in the future.