Histopathologic lesion incidence

No treatment-related gross or histopathological lesions in the liver were observed in rats in the chronic experiment by NTP (1986), but dosed male mice had increased coagulative necrosis and hepatocytomegaly, along with increased incidences of hepatocellular adenomas and carcinomas (see Section 2.2.2.8 on carcinogenicity). Female mice, however, did not have treatment-related lesions in the liver. The highest dose (500 mg/kg/day) is indicated as a NOAEL for liver effects in rats, while the low dose (250 mg/kg/day) is indicated as a LOAEL for non-neoplastic liver lesions in... 

Information regarding gastrointestinal effects in animals after inhalation exposure to chromium or its compounds is limited. Histological examination of the stomachs of rats exposed to sodium dichromate dihydrate at 0.2 mg chromium(VI)/m3 for 28 or 90 days revealed no abnormalities (Glaser et al. 1985). In mice exposed intermittently to 4.3 mg chromium(VI)/m3 as calcium chromate for 18 months, small ulcerations in the stomach and intestinal mucosa were reported to occur occasionally, but the incidence in the treated mice, in controls, or other details regarding these lesions were not reported (Nettesheim et al. 1971). No treatment-related histopathological lesions were found in the stomach, large intestine, duodenum, jejunum, or ileum of rats chronically exposed to chromium dioxide at 15.5 mg chromium(IV)/m3 (Lee et al. 1989). 

Respiratory Effects. Male and female Fischer 344 rats and B6C3Fj mice were given oral doses of 0, 25, 50, 100, 200, 400, or 600 mg/kg/day benzene in com oil for 120 days (NTP 1986). No histopathological lesions were observed in lungs, trachea, or mainstream bronchi. After chronic-duration exposure to 50, 100, or 200 mg/kg/day (male rats) or 25, 50, or 100 mg/kg/day (female rats, male and female mice), no histopathological lesions were observed in trachea, lungs, or mainstream bronchi in rats (NTP 1986). In mice, a significantly increased incidence of alveolar hyperplasia was observed at 50 and 100 mg/kg/day in females and at 100 mg/kg/day in males. 

Juvenile dermatomyositis (JDM) is perhaps the most uniform, in terms of clinical and histopathological features, of the whole PM/DM disease complex. Presentation may be before 5 years of age with peak incidence between 8 and 12 years. The disease may remit and recur until well into young adult life. The skin lesions include a facial rash in butterfly distribution across nose and cheeks. Erythematous skin changes are seen over extensor surfaces of joints, especially knees, knuckles and elbows. Muscle involvement is generally evident some time later and takes the form of weakness and stiffness, particularly affecting shoulder and pelvic musculature. Proximal muscles are often worse affected than distal muscles and extensors worse than flexors. In the absence of prompt and effective treatment contractures may occur at elbows, ankles, knees, and hips. Subcutaneous calcification and skin ulceration may be found calcification of deeper-lying connective tissue may be apparent on X-ray. 

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