Objective: The purpose of the study was to evaluate the relationship between mucous membrane pemphigoid and a state of hypothyroidism. The study included analysis of the dental charts of 40 subjects with clinically and histologically confirmed diagnosis of mucous membrane pemphigoid and 35 age- and gender-matched subjects, from the same clinic, with no diagnosis of vesiculo-ulcerative lesions. Results: Thirteen subjects from the pemphigoid group (32%) had a hypothyroid condition, compared to four subjects (11%) from the control group (P = .030). Within the mucous membrane pemphigoid subjects who had a history of hypothyroidism, 83% were females. Although cases of hypothyroidism and autoimmune blistering oral disorders such as lichen planus were described in the past, this is the first report of an association between mucous membrane pemphigoid and hypothyroidism. A case report describes a patient who presented with desquamative gingivitis and vesicular lesions, and was diagnosed with mucous membrane pemphigoid and Hashimoto's thyroiditis. Conclusion: The general dental provider should be familiar with mucous membrane pemphigoid and the potential association with hypothyroidism. Early diagnosis of hypothyroidism is significant because replacement may prevent a significant morbidity associated with this condition. Therefore, the general dental provider should be aware of oral conditions presented as desquamative gingivitis and their potential association with hypothyroidism. Keywords: hypothyroidism, mucous membrane pemphigoid