RETROBULBAR CONNECTIVE TISSUE CHANGES IN MALIGNANT EXOPHTHALMOS

Abstract

The histological changes in the retrobulbar connective tissue of patients with malignant exophthalmos have been thoroughly investigated. Most authors are in agreement about the character of the changes (Aird, 1940, Brain & Turnbull, 1938, Dobyns, 1946 a, b, Falconer & Alexander, 1952, Friedenwald, 1932, Merrill & Oakes, 1933, Mulvany, 1944, Naffziger, 1933, Smelser, 1937, 1939), but the cause and genesis of the tissue changes have been matters of dispute. Smelser (1937) pointed out the resemblance between the picture in malignant exophthalmos in man and in the thyrotrophin-induced changes in the guinea pig. It is evident (Paulson, 1937) that the water-binding properties of the retrobulbar tissue are increased in exophthalmos. These augmented water-binding properties could be explained by the investigations of Asboe-Hansen & Iversen (1951) and Ludwig et al. (1950). These investigators showed that the ground substance of the retrobulbar connective tissue, and especially the mucopolysaccharide hyaluronic acid, was definitely increased in experimentally induced exophthalmos in the guinea pig. Hyaluronic acid is strongly water-binding, as is well known. An increased uptake of radioactive sulphur (35S) of the retrobulbar connective tissue of guinea pigs during administration of thyrotrophic hormone has been demonstrated by Lamberg et al. (1956). This is a strong evidence of increase of sulphuric mucopolysaccharides. Asboe-Hansen & Iversen (1951) observed an accumulation of connective tissue mast cells under such conditions, and these cells are thought to produce mucopolysaccharide components of the connective tissue ground substance (Asboe-Hansen, 1951). In patients with malignant exophthalmos, Asboe-Hansen et al. (1952) observed increased amounts of acid mucopolysaccharides in the connective tissue of the pretibial area and in the skeletal muscle fibres inside the sarcolemmic membrane. The intrasarcolemmic mucopolysaccharide masses appear as »halfmoons« in transverse sections of the muscle fibres. These phenomena may offer a clue to the nature of the muscular weakness often seen in thyro-hypophyseal disorders. In exophthalmos in experimental animals, such phenomena, however, are not observed in the musculature.