Diagnosis

We frequently find some difficulty here. The chief points to remember in regard to lichen are the dry and thickened state of the skin and the presence of papules, which are always to be found, if the disease is in patches, at the extending edge; the hard feel of the papules, and their tingling or itchiness. Lichen simplex and scabies may be confounded. Lichen is uniform, scabies multiform. In scabies, besides papules there are vesicles, often pustules, and the papules are not so closely aggregated; the eruption also is in the line of flexion, not, as in lichen, in that of extension, i.e. lichen is seen chiefly on the outer aspect of the arm; it may occur on the back of the hands and fingers, but it is not interdigital. Lichen simplex, never occurs in the feet; it is common on the face; scabies is not. In scabies, too, there is the characteristic vesicle and sillon, whilst the disease is contagious and easily removed by sulphur treatment.

Phtheiriasis may simulate lichen, but it is associated with an unhealthy, relaxed, muddy, dirty state of the skin - flabby is the word, the papules (which are pale) are fewer in number, and each is marked at its apex with a dark speck (dried blood) effused as the result of scratching. The skin is not thickened and dry, as in lichen, nor is there any attempt at scaliness, as in lichen, nor aggregation of papules into patches or groups. Phtheiriasis is essentially a disease of advanced age. It occurs in the uncleanly, and there is often a peculiar urticated state of skin, seen very markedly on the back and chest, produced by an exaggeration of the spaces enclosed by the normal furrows. Phtheiriasis does not occur about the face; the sensation is one of formication, and is altogether out of proportion to the local disease, whilst pediculi may frequently be detected in the folds of the linen.


Lichen agrius resembles eczema, but the latter is moist and discharging, occurs in delicate and thin, not in harsh dry skins; again, the history and edge of the patch in lichen point to the existence of papules; then the patch is much thicker and harsher than in eczema, and wants its thick yellow crusts; the latter in lichen are thin, pretty few, and "flimsy".

It is important to remember that scabies may be com­plicated with lichen, and the latter may be set up as the result of irritation in scabies. One sees this state of things very frequently in the hot season - the irritation of a few scabious spots bringing out a pretty general lichen.