Bentonite cat litter is one of the most popular types of litter used in cat litter boxes worldwide. One of its components is crystalline silica, which when inhaled is a risk factor for silicosis. While silicosis is considered an occupational lung disease, it seems that individuals with no occupational exposure, such as cat owners, may also be affected. In this case report we present an unusual case of chronic silicosis with sarcoid-like reaction complicated by end-stage renal failure from exposure to bentonite cat litter.
A 44-year-old woman was admitted to the hospital with end-stage renal failure, productive cough and decreased exercise tolerance. On evaluation, a transbronchial lung biopsy was performed. The X-ray photoelectron spectroscopy revealed the presence of silicon in the lung tissue specimen, as well as in the patient’s cat litter. A detailed patient’s history excluded occupational exposure to crystalline silica, however she acknowledged that she had owned 9 cats at home. In a 44m2 apartment, she had had 9 cat litter boxes, which all had been filled with bentonite cat litter for 18 years.
After an extensive workup, a diagnosis of chronic silicosis with sarcoid-like reaction complicated by end-stage renal failure from exposure to bentonite cat litter was made. Renal deterioration appeared to result from chronic hypercalcemia, which was a consequence of extra-renal overproduction of calcitriol in activated alveolar macrophages, frequently seen in granulomatous diseases.
Our patient had an abnormally large and longtime exposure, but similar health complications may occur, for example, in workers in the zoological industry. It seems reasonable to consider our case report as a strong call for bentonite cat litter manufacturers to place on the packaging information on potential health complications, along with a recommendation to use protective masks when cleaning the litter box.