[Thyroid pathology and lymphoproliferative diseases]

Four cases are reported, of an association between a thyroidal illness (1 hypothyroidism, 3 hyperthyroidism) on one hand, and a lymphocytic proliferation and/or monoclonal gammapathy on the other. The following findings: HLA B8 or DrW3 in 3, antithyroid antibodies at a very high level in 2, and thyroid stimulating immunoglobulin in 2 support the conclusion of thyroidal diseases of auto-immune nature. Simultaneous appearance of both thyroidal and hematologic illness favors the hypothesis of a non coincidental association. A direct thyroidal activity of the monoclonal paraprotein has been found only once among the 4 published and our 2 cases in which it has been studied. A more likely link would be a common physiopathology: a functional deficiency of T suppressor lymphocytes allowing the proliferation of a cellular clone producing an abnormal immunoglobulin, would also allow the development of a thyroidal illness when favored by a genetic predisposition.