Pulmonary sarcoidosis: could mycoplasma-like organisms be a cause?

The etiology of sarcoidosis is unknown but an unusual bacterial agent is possible. Mycoplasma-Like Organisms [MLO] are obligate intracellular cell wall deficient bacteria with a distinctive ultrastructural appearance. MLO are a common cause of various transmissible plant diseases. Despite over 25 years of effort MLO remain uncultivated. Molecular biologic studies indicate MLO are only distantly related to extracellular cultivable mycoplasma. Diagnosis of MLO diseases is based chiefly on detection of the organisms in infected cells by electron microscopy. Recently MLO have been detected by electron microscopy within leucocytes in sterile inflamed aqueous and vitreous humor from patients with idiopathic chronic uveitis including sarcoidosis uveitis. Preliminary molecular biologic studies suggest that human MLO are quite closely related phylogenetically to plant MLO. Inoculation of human uveitis MLO into mouse eyelids produced chronic uveitis and lethal systemic granulomatous disease with MLO within leucocytes and endothelial cells in the disease sites. The MLO induced animal pulmonary disease resembled sarcoidosis. This report describes abnormal intracellular bodies consistent with MLO within leucocytes and endothelial cells adjacent to the granulomas in transbronchial biopsies from 9 corticosteroid untreated sarcoidosis patients versus none in 4 control lungs.