Coal forms from the accumulation of plant debris, usually in a swamp environment. When plant debris dies and falls into the swamp the standing water of the swamp protects it from decay. Swamp waters are usually deficient in oxygen, which would react with the plant debris and cause it to decay.
Porokeratosis is generally considered to be a benign condition though malignant transformation has been seen in all but the punctate variety, necessitating regular followup of patients with porokeratosis (Maubec et al., 2005; Sasson & Krain, 1996).
Although lichen planopilaris is a distinct form of scarring alopecia, it can be rather difficult to diagnose with certainty. When accompanied by characteristic lesions of lichen planus on the skin and oral mucosa, lichen planopilaris is easily ascertained.isease activity is limited to the hair-bearing periphery of cicatrized alopecia, and pustules are absent in this kind of alopecia. Features of end-stage lichen planopilaris can mimic other primary cicatricial alopecias, making it difficult to reach a proper diagnosis.