• true (idiopathic),

• microbial,

• Infantile,

• seborrhoeic,

• occupational eczemas.

Each of these forms may be:

• acute,

• subacute or

• chronic.

True (Idiopathic) Eczema

Erythema (eczema erythematosum) appears at the onset against the background of which microvesicles (to the size of a pin head), papules (mostly exudative) form (eczema vesiculosum, papulovesiculosum, papulosum). The microvesicles in the centre of the focus rupture, the serous exudate seeps onto the skin surface and produces oozing areas with a macerated and scaling horny layer (eczema madidans). Careful examination of the focus will reveal numerous 'point' erosions from which small drops of serous exudate emerge (serous wells).

The clinical picture is characterized by clear-cut pleomorphism and variegated eruptions. Erythematous spots, microvesicles, papules, erosions, and numerous scratches may be simultaneously encountered at the peak of the inflammatory process. True and false (evolutional) pleomorphism, i.e. the simultaneous presence on the affected areas of vesicles, erythema, exudative papules, small erosions with drop oozing, scales, crusts, and other lesions, the interrupted character of the foci of affection, and the alternation of the affected skin areas with healthy areas ('archipelago' pattern) are extremely characteristic of the eczematous process. The eruptions are symmetric and tend to spread to the skin on the upper and lower limbs and trunk. The patients are troubled by itching of various intensity, which is conducive to the development of neurotic disturbances with insomnia. With the gradual abatement of the inflammatory phenomena, typical of an eczematous process, the oozing is replaced by the formation of crusts and scales and the appearance of crusts (eczema crustosum, eczema squamosum) and secondary pigmento-vascular or depigmented spots which resolve gradually. Foci of dry and peeling skin with the formation of cracks in the horny layer (eczema craquele) may arise. Callous hyperkeratotic tissues with cracks sometimes form on the palms and soles in protracted chronic eczema (eczema tyloticum). The course of eczema is often aggravated by accompanying pyogenic infection; pustules and purulent crusts form in such cases (eczema impetiginosum).

Despite the marked pleomorphism that is typical of eczema, one type of the morphological lesions may sometimes be prevalent, in which case it is possible to diagnose the forms of true eczema mentioned above. It should be emphasized that the transformation of acute weeping eczema to the chronic form usually occurs gradually and is attended with increasing tissue infiltration and the change of active hyperemia to passive hyperemia. A chronic eczematous process often exacerbates with the reappearance of active hyperemia, microvesicles, and oozing and intensification of itching.

The following varieties of true eczema are known.

Pruriginous eczema. This form is characterized by eruption of small, the size of a millet, papulovesicular lesions on an indurated base; they neither rupture nor form erosions. The foci of affection are localized on the face, the flexor surfaces of the elbows and knees, in the inguinal region, and on the extensor surfaces of the limbs; the lesions recur often and the disease takes a chronic course. As the result of the protracted course, scratches, excoriations, and deposits of cellular infiltrate, the skin on the affected areas becomes rough, pigmented, dry, chapped, and undergoes lichenification. Attacks of itching and severe neurotic reactions with insomnia are very characteristic of this dermatosis. The disease usually exacerbates in the winter and a remission occurs in the summer.

Dyshidrotic eczema (eczema dyshidroticum) is characterized by the formation of small, the size of a pin head, and hard to the touch vesicles on the sides of the fingers and toes and sometimes on the palms and soles. Large multiloculate bullae are encountered less frequently. Lying in the epidermis, the vesicles are seen through it and resemble boiled rice. The patients are often troubled by severe itching. The vesicles may rupture and turn into excoriations or they dry up and form flat yellowish crusts. Sharply demarcated foci of affection form later and have a marked inflammatory colour, which distinguishes dyshidrotic eczema from true dyshidrosis (dyshidrosis vera) and epidermophytids of the palms (in dyshidrotic epidermophytosis mycelial threads of the epidermophyton fungus are found on the covers of the vesicles on the arch of the foot).