ARTICLE
A 59-year-old man was referred to our clinic in September 1997 with a
long history of severe itching on both his lower legs. At clinical examination
we found inconspicuous, pruritic eruptions of small brownish macules and
papules distributed typically in a rippled, symmetric fashion on the ventral
site of the lower leg (Figs. 1
and 2). The remaining integument and all laboratory
investigations were normal.
Lichen amyloidosus
The term "amyloidosis" was coined because of the deposits of amyloid
in organs and includes the systemic and the localized type of cutaneous
amyloidosis (LCA). LCA can be subdivided into two groups: the primary
and secondary cutaneous forms of amyloidosis. Primary cutaneous amyloidosis
type comprises lichen amyloidosus (LA), and the macular and the rare nodular
form. Members of the secondary cutaneous forms include sweat gland tumors,
pilomatrixoma, dermatofibroma, seborrhoeic keratosis, solar elastosis,
actinic keratosis, basal cell carcinoma, Bowen's disease a.o. [1].
In this case, the correct diagnosis of LA was
confirmed by histological and histochemical examination of a skin biopsy.
On haemalaun-eosin staining, we found deposits which expanded the papillary
dermis and displaced the rete ridges laterally (Fig.
3a). Using special stains such as methyl violet staining (Fig.
3b), staining with congo red followed by polarized light microscopy
and PAS-staining, we were able to characterize these structures as amyloid.
Other useful histochemical stains are included in Table
I. The overlying epidermis showed irregular acanthosis and hyperkeratosis,
which is a characteristic finding in later lesions.
The pathogenesis of LA is not entirely clear.
The most popular hypothesis suggests that because of the severe itching
and as a consequence of the scratching there is focal epidermal damage
and filamentous degeneration of keratinocytes, followed by apoptosis and
conversion of filamentous masses (colloid bodies) into amyloid K (k =
keratin) material in the papillary dermis. It has been postulated that
in LA, specific immunological tolerance to the presence of colloid bodies
in the papillary dermis favors their transformation into amyloid by macrophages
and fibroblasts, whereas in lichen planus, for example, a brisk inflammation
response ensures their removal. The fact that dermal amyloid K deposits
cross-react immunohistochemically with keratin, supports this hypothesis
[4, 5]. Recently, Chang et al. [2] reported that EBV may be associated
with some cases of LA, but the true aetiological role of EBV in LA remains
unknown.
For LA different treatment regimens exist. Systemic
antihistamines are effective at reducing the pruritus, which is the important
pathophysiological step in LA. As specific therapy, it is possible to
use topical steroids, dermabrasion or DMSO [3]. Systemic treatment with
etretinate may also be beneficial in some patients, but not in all [1].
REFERENCES
1. Breathnach SM. Amyloid and amyloidosis. J Am Acad Dermatol
1988; 18: 1-16.
2. Chang YT, Liu HN, Wong CK, Chow KC, Chen KY. Detection of Epstein-Barr
virus in primary cutaneous amyloidosis. Br J Dermatol 1997; 136:
823-6.
3. Kobayashi T, Yamasaki Y, Watanabe T, Onoda N. Extensive lichen amyloidosus
refractory to DMSO. J Dermatol 1995; 22: 755-8.
4. Weyers W, Weyers I, Bonczkowitz M, Diaz-Cascajo C, Schill WB. Lichen
amyloidosus: a consequence of scratching. J Am Acad Dermatol 1997;
37: 923-8.
5. Yoneda K, Watanabe H, Yanagihara M, Mori S. Immunohistochemical staining
properties of amyloids with anti-keratin antibodies using formalin-fixed,
paraffin-embedded sections. J Cutan Pathol 1989; 16: 133-6.
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