Chloracne is a skin disease that is characteristic of exposure to TCDD and other cyclic organochlorine compounds. It shares some pathologic processes (the occlusion of the orifice of the sebaceous follicle) with more common forms of acne (such as acne vulgaris), but it can be differentiated by the presence of epidermoid inclusion cysts, which are caused by proliferation and hyperkeratinization (horn-like cornification) of the epidermis and sebaceous gland epithelium. Although chloracne is typically distributed over the eyes, ears, and neck, patterns of chloracne among chemical industry workers exposed to TCDD also include the trunk, genitalia, and buttocks (Neuberger et al., 1998).
Chloracne has been studied extensively and is used as a marker of exposure in studies of populations exposed to TCDD and other organochlorine compounds, such as polychlorinated biphenyls (PCBs) and pentachlorophenol. It is one of the few findings consistently associated with such exposure and is a well-validated indicator of high exposure to those compounds, particularly TCDD (Sweeney et al., 1997/98). If chloracne occurs, however, it appears shortly after the chemical exposure, not after a long latency. Although it is refractory to acne treatments, it usually regresses over time. Therefore, new cases of chloracne would not be the result of exposures during Vietnam and are not a concern for this report. It also should be noted that lack of chloracne does not necessarily indicate the absence of exposure to substantial levels of TCDD, as is apparent from studies of individuals exposed in the Seveso accident. There is not necessarily a correlation between serum concentrations of TCDD and the occurrence or severity of chloracne.
The committee responsible for Veterans and Agent Orange: Health Effects of Herbicides Used in Vietnam (hereafter referred to as VAO; IOM, 1994) determined there was sufficient evidence of an association between exposure to at least one compound of interest and chloracne. Additional information available to the committees responsible for Veterans and Agent Orange: Update 1996 (IOM, 1996), Update 1998 (IOM, 1999), Update 2000 (IOM, 2001), and Update 2002 (IOM, 2003) did not change that finding. Reviews of the studies that underlie the finding can be found in the earlier reports.
No relevant occupational or environmental studies have been published since Update 2002.