Cat litter is a possible trigger for sarcoidosis: Figure 1–

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Abstract
To the Editors: Sarcoidosis is characterised by cellular immune activity with noncaseating granuloma formation in various organ systems with a multifactorial cause. Many causative agents are considered to be involved in the pathogenesis [1–5]. Gene–environment interactions offer the potential for strengthening the evidence of causation between exposures and sarcoidosis. It is important to identify every potential exposure to triggers in order to avoid irreversible damage. Inorganic agents, including silica, have been reported to initiate inflammation and granulomatous reactions [6, 7]. It is well known that cats can cause allergic reactions, but less is known about the association of inflammation and cat litter. We propose that silica, the major component of cat litter, might be such an agent. We report a case of biopsy-proven sarcoidosis with birefringent material, mainly silica, within the lung biopsy specimen. The patient had no relevant occupational history, but had cats and was extensively exposed to silica-containing cat litter. Initially, the patient improved after starting immunosuppressive drugs and terminating contact with litter. However, she deteriorated twice after autoprovocation (re-exposure) to cat litter. After changing the silica-containing cat litter for litter without silica, her clinical condition improved substantially. Obviously, she appeared to be “hypersensitive” not to the cats but to the cat litter. A 44-yr-old female was admitted to the former ILD Care Team (a tertiary referral centre) of the Dept of …

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