LOCALIZED THYMIC LANGERHANS CELL HISTIOCYTOSIS AND ITS RELATIONSHIP WITH MYASTHENIA-GRAVIS - IMMUNOHISTOCHEMICAL, ULTRASTRUCTURAL, AND CYTOMETRIC STUDIES

Objective.-It has been suggested that localized Langerhans' cell histi ocytosis may represent an exaggerated form of a proliferative process that has been reported in a few patients with myasthenia gravis. To ev aluate the relationship between thymic Langerhans' cell proliferation and myasthenia gravis, we analyzed a rare case of localized thymic Lan gerhans' cell histiocytosis and examined thymic Langerhans' cell distr ibution in myasthenic and control patients. Design.-Immunohistochemica l, ultrastructural, and image cytometric DNA analyses were performed o n the index case. Immunostaining for S100 was performed on 20 addition al thymuses, 10 from patients with myasthenia gravis and 10 from contr ol patients. Results.-Immunohistochemical studies revealed no increase in Langerhans' cells in the surrounding thymic tissue of the index ca se. No difference was found between the number of Langerhans' cells in the remaining thymuses of myasthenia patients compared with the contr ol group, and no micronodular proliferations were identified in either group. Conclusions.-Localized thymic Langerhans' cell histiocytosis i s an unusual lesion that is associated with myasthenia gravis in some patients. In the few cases reported at present, however, the lesion do es not appear to be related pathogenetically to myasthenia gravis.