“Egg Shell” Calcifications In Silicosis

Abstract

CHARACTERISTIC calcium densities of apparently unique morphology occur in chest roentgenograms of men having silicosis. These shadows are seen as more or less regular rings in the hilar or mediastinal regions of the chest. They have been designated as egg-shell, Eierschalen, or mulberry calcifications. They are circular or ovoid in character and consist of an irregular peripheral shell with a faint stippling throughout the enclosed tissue. Considerable divergence of opinion exists as to the cause and significance of this particular formation. There has, unfortunately, been a paucity of autopsy studies to clarify the problem. Lommel (2) was of the opinion that calcium is deposited in inflamed and dilated sinuses within the lymph node capsule and other similarly dilated lymphatic spaces. He states that similar calcifications are seen in the extreme periphery of the lung. He also mentions fine, delicate ring forms which may be early or transitional stages of the same process. Mild cases with “snow-storm” lung changes sometimes show the calcifications very clearly. Lommel reports a 20 per cent incidence of calcifications in cases of silicosis without clinically proved tuberculosis. Sweany et al. (10) show that the annular densities are calcareous and express the opinion that, "in cases of silicosis, such a formation represents collateral infection, chiefly by the tubercle bacillus." Sweany (9) does state that the lymph node changes are characteristic and identifies the subcapsular location of the calcium infiltration. Schulte and Husten (7) were of the opinion that the shadows represent dense silicotic connective tissue around bronchi, extending into the lung fields. Davies (1) presents twenty-three cases and discusses the probabilities. (a) Calcification exists, in which case it is due to silico-tuberculosis and must be associated with tuberculous infection. It may be due to a degenerative process following a silicotic infiltration of the lung root glands attracting lime salts, which become deposited in them. (b) Calcification is not present, the shadows representing silicotic nodules in the lung itself. Riemer (4) is of the opinion that the densities may represent the results of inhaled calcium along with the silica dust. He presents four cases having no clinical evidence of tuberculosis. In one the tuberculin reaction was negative. Rigler (5) refers to the calcification of the lymph nodes in silicosis as “classic.” The present study is a correlation of history, clinical and roentgenographic findings, and histopathology, in an attempt to produce a clearer picture of this phase of silicosis and to determine the significance of the unique morphology of the calcium deposits. Preliminary Remarks Preliminary remarks will aid in a more critical evaluation of the material and data, which were obtained at the San Francisco City and County Hospital.