New research has shown evidence that infectious causation may be partly responsible for PB. First, some types of baldness have already been shown to be a result of infectious diseases such as influenza, typhus, lyme meningitis, tick-borne encephalitis (Cimperman, 1999), HIV (Jan & Roudier-Pujol, 2000), scarlet fever, and pneumonia (Weigand, 1969). Second, there is growing evidence of the presence of inflammation in the scalp of balding individuals (Kligman, 1988; Young et al., 1991; Jaworsky et al., 1992; Piérard et al., 1996; Sueki et al., 1999; Mahé et al., 2000). Finally, PB has been associated with an increased risk of heart disease (Herrera & Lynch, 1990; Trevisan et al., 1993; Ford et al., 1996; Sasmaz et al., 1999). Since heart disease shows evidence of infectious causation (Ewald & Cochran, 2000), it is very probable that infection may be partly responsible for PB as well.

The presence of inflammation in the scalps of balding patients is now beginning to be recognized. Kligman (1988) was the first to notice the difference in the degree of inflammation in balding as opposed to control subjects. He observed the presence of substantial lymphohistiocytic infiltrate and abnormal inflamed streamers in the scalps of balding men, both of which were rare in non-bald controls. The inflammations in the scalp were localized around the infundibulum and sebaceous glands, and numerous lymphocytes, macrophages, and mast cells were found in those areas. The density of follicles was not noticeably diminished, although some were destroyed by the intense inflammatory infiltrate. Kligman explained that the chronic inflammation prevents the anagen follicles from being fully reconstructed during each new cycle, which explains the shortening of the anagen phase in PB. He concluded his paper by stating that PB is an “inflammatory disorder that should not be construed as premature aging.” He hypothesized that suppression of the inflammation could decelerate the process of PB. Furthermore, he noted that bald people often report scaling and itching during the early stages, presumably because of the inflammation. Finally, Kligman suggested studying PB in connection with seborrheic dermatitis and dandruff. Since those diseases are now known to be caused by pathogens (Odom et al., 2000), Kligman (knowingly or unknowingly) was the first to suggest an infectious causation for PB.

(http://www.autoadmit.com/thread.php?thread_id=3831408&forum_id=2#34936945)