"Non-secretory" plasma cell dyscrasia with normal serum immunoglobulins.

A well documented case of non-secretory myelomatosis with extensive skeletal lesions has been studied by immunohistologic techniques, electron microscopy, various electrophoretic procedures and different studies of serum and urine. In addition, the various lymphocyte populations have been studied by immunofluorescent techniques, rosette formation and stimulation with PHA and PWM mitogens. The ultrastructural studies revealed a well preserved structure of most of the plasma cells, often with a prominent nucleolus. The Golgi apparatus (GOL) was often large and in some cells there appeared to be a striking development of non-granular (smooth) endoplasmic reticulum in association with the GOL. Various non-crystalline inclusions were seen outside the cisternae of the endoplasmic reticulum. The cells contained large amounts of immunoglobulins of the IgG (kappa) class. No paraprotein was present in serum. Normal amounts of serum immunoglobulins were detected. No abnormalities could be demonstrated in the B or T cell system. It is concluded that the defect must be localized to the plasma cells themselves and not to the precursor cells of the B system.