[Lichen amyloidosus--disease entity or the effect of scratching]

In current textbooks of dermatology, lichen amyloidosus is said to be a papular, intensely pruritic type of amyloidosis of unknown aetiology. When this concept was developed, there was no way of discriminating between the different types of amyloid. It is now known that amyloid in lichen amyloidosus is not derived from immunoglobulins or serum proteins, as it is in systemic amyloidoses, but from keratin peptides of necrotic keratinocytes. Even several years ago, chronic scratching was invoked as a possible cause of damage to keratinocytes in lichen amyloidosus. In support of this hypothesis, four cases are presented. Apart from amyloid in the papillary layer, all biopsy specimens revealed histopathological signs of chronic scratching (epithelial hyperplasia with hypergranulosis and compact orthokeratosis, coarse collagen in vertical streaks in the stratum papillare), such as are also found in prurigo nodularis and lichen simplex chronicus. Lichen amyloidosus is considered to be a variant of these conditions. Just as in prurigo nodularis and lichen simplex chronicus, pruritus seems to be the cause and not a symptom of the papular skin lesions. Consequently, treatment of lichen amyloidosus should not be directed at removing amyloid, but at improving the pruritus.