Acute febrile neutrophilic dermatosis (AFND; Sweet syndrome) is characterized by a constellation of symptoms and findings: fever, neutrophilia, and tender erythematous skin lesions that typically show an upper dermal infiltrate of mature neutrophils. Whereas some cases are idiopathic, others have been associated with a variety of disorders. In this report, we describe the occurrence of AFND with chronic lymphocytic thyroiditis (Hashimoto thyroiditis) and preexisting psoriasis. This is the first case report of the association of chronic lymphocytic thyroiditis with AFND from the United States and only the third reported in the world's literature. Because the coexistence of these disorders is rare, an underlying common pathogenic mechanism is a possibility. We postulate this to be CD4(+) T-cell dysfunction.