True about silicosis is?

Ans. is 'd' i.e., All of the above Silicosis* Silicosis is a slowly progressive disease lung disease caused by inhalation of crystalline silicon dioxide (silica). Currently, it is the most prevalent occupational disease in the world.* Silica occurs in both crystalline and amorphous forms but crystalline forms are much more fibrogenic. The crystalline form are quartz, and crystobalite.* Silicosis is characterized in its early stages by nodules in the upper zones of the lung. As the disease progresses these nodules may coalesce into hard collagenous scars. Fibrotic lesions occur in the hilar lymph node and pleura. Sometimes thin sheets of calcification occur in the lymph nodes and are seen radiographically as egg shell calcification i.e. (calcium surrounding a zone lacking calcification. It the disease continues to progress, expansion and coalescence of lesions produce progressive massive fibrosis.* Histologically the lesions of silicosis consist of concentric layers of hyalinized collagen surrounded by a dense capsule of more condensed collagen. Examination of the nodules by polarized microscopy reveals the birefringent silica particles.