Pathogenesis, clinical features and pathology of chronic arsenicosis.

Arsenicosis is a multisystem disorder, with virtually no system spared from its vicious claw; though its predominant manifestations are linked to cutaneous involvement. Cutaneous effects take the form of pigmentary changes, hyperkeratosis, and skin cancers (Bowen's disease, squamous cell carcinoma, and basal cell epithelioma). Peripheral vascular disease (blackfoot disease), hypertension, ischemic heart disease, noncirrhotic portal hypertension, hepatomegaly, peripheral neuropathy, respiratory and renal involvement, bad obstetrical outcome, hematological disturbances, and diabetes mellitus are among the other clinical features linked to arsenic toxicity. The effects are mediated principally by the trivalent form of arsenic (arsenite), which by its ability to bind with sulfhydryl groups present in various essential compounds leads to inactivation and derangement of body function. Though the toxicities are mostly linked to the trivalent state, arsenic is consumed mainly in its pentavalent form (arsenate), and reduction of arsenate to arsenite is mediated through glutathione. Body attempts to detoxify the agent via repeated oxidative methylation and reduction reaction, leading to the generation of methylated metabolites, which are excreted in the urine. Understandably the detoxification/bio-inactivation process is not a complete defense against the vicious metalloid, and it can cause chromosomal aberration, impairment of DNA repair process, alteration in the activity of tumor suppressor gene, etc., leading to genotoxicity and carcinogenicity. Arsenic causes apoptosis via free radical generation, and the cutaneous toxicity is linked to its effect on various cytokines (e.g., IL-8, TGF-beta, TNF-alpha, GM-CSF), growth factors, and transcription factors. Increased expression of cytokeratins, keratin-16 (marker for hyperproliferation) and keratin-8 and -18 (marker for less differentiated epithelial cells), can be related to the histopathological findings of hyperkeratosis and dysplastic cells in the arsenicosis skin lesion.

Cryptic exposure to arsenic.

Arsenic is an odorless, colorless and tasteless element long linked with effects on the skin and viscera. Exposure to it may be cryptic. Although human intake can occur from four forms, elemental, inorganic (trivalent and pentavalent arsenic) and organic arsenic, the trivalent inorganic arsenicals constitute the major human hazard. Arsenic usually reaches the skin from occupational, therapeutic, or environmental exposure, although it still may be employed as a poison. Occupations involving new technologies are not exempt from arsenic exposure. Its acute and chronic effects are noteworthy. Treatment options exist for arsenic-induced pathology, but prevention of toxicity remains the main focus. Vitamin and mineral supplementation may play a role in the treatment of arsenic toxicity.