The thymic "myoidzellen" and myasthenia gravis

It has been known for a long time that there is an association of some sort between thymic lesions, thymomas in particular, and myasthenia gravis.¹More recently, cross-reactions have been demonstrated between antimuscle antibodies in the sera of individuals suffering from myasthenia gravis and certain cells of the thymus.^2,3There is little doubt that the reactive elements in the thymus are not entodermal reticular elements, but actual muscle cells, the "myoidzellen" of the old anatomists.⁴ Elongated, occasionally stellate, eosinophilic cells containing cross-striated fibrils have been reported among thymocytes and reticular cells of the thymus in a variety of vertebrates. First described by Mayer⁵in the frog's thymus, they were observed by him as long, spindle-shaped elements showing distinct striations and closely resembling rudimentary skeletal muscle fibers. Pensa⁶found these strange cells to be particularly numerous and well developed in the thymus of chickens and called