Serological detection of thymoma in myasthenia gravis.

A purified citric acid extract (CAE) was prepared from skeletal muscle and coated onto sheep red cells for use in an indirect hemagglutination test. Out of 64 MG sera examined, only 5 contained antibodies to the CAE. Radiological evidence of a thymoma was found in 1, but thymectomy revealed a lymphoepithelioma in all 5 patients. In 4 of the patients, the tumor was very small or medium-sized. None of the CAE-negative patients had clinical, radiological or other evidence of a thymoma. The test in therefore a supplementary diagnostic method for the detection of a thymoma at an early stage.