[The histological substrate of the extraocular muscle thickening seen in dysthyroid orbitopathy (author's transl)].

The diagnosis of dysthyroid orbitopathy can be confirmed in over 80% of cases by demonstrating thickened extraocular muscles on computertomograms. The criteria are briefly discussed and the histological picture of the muscle thickening is described. The changes are variable and depend upon the course of the disease. Fatty infiltration is the most important factor causing muscle thickening, mucopolysaccharide deposition and fibrosis contribute less to the increased muscle volume, while inflammatory cell infiltration and proliferation of the endomysium play a minor role. The fatty infiltration and fibrosis, representing late changes, are probably therapy resistant in contrast to the other changes.