Selective IgM deficiency in a patient with Hashimoto's disease.

A 70-year-old man with Hashimoto's disease had selective IgM deficiency, while other immunoglobulin levels were normal. In vitro mixing experiments were carried out in which B cells and T cells from the patient and from a healthy control donor were co-cultured in the presence of pokeweed mitogen, in order to investigate the etiology of IgM hypoproduction. The results indicated that the patient had B-cell dysfunction, involving the impairment of B-cell differentiation. In addition, both IgG of the healthy control donor and thyroid hormone may play important roles in the pathogenesis of this case.