Miliaria

MILIARIA (from the Latin mi-lar-ia), a millet-seed-like rash, sweat rash, a collective name for a group of so-called acute sweating eruptions (sudamina). M. crystallina, M. rubra, and M. alba are distinguished. While the last two forms represent only different stages of the same type of sweat rash, M. crystallina appears to be a completely independent dermatological unit. Miliaria crystallina (M. pectoralis, M. cardiaca), being a consequence of excessive sweating (hyperhidrosis), develops during profuse sweating in various infectious febrile diseases, often before agony. Epidemic outbreaks of M. crystallina (M. epidemica) (Kyrle) are also observed. Jadassohn and Mirolyubova showed that M. crystallina can also occur at normal body temperature without disturbance of the general condition, for example under tight bandages. - Clinical picture. On completely normal skin of the trunk, neck, and limbs, small, the size of a millet grain, densely located, transparent superficial blisters form; in some cases the eruption can only be detected by running a finger over the affected skin. Subjective sensations are usually absent. The entire skin process ends, as a rule, in 3–4 days with insignificant peeling; in some cases M. crystallina drags on for several weeks. Histological examination reveals no changes except for blisters in the stratum corneum; at the bottom of the blisters, the excretory duct of a sweat gland is often detected (Torok, Unna). Examination of the contents of a miliaria crystallina blister shows an acidic reaction, absence of protein, and poverty in dense components (18%), of which 4% are inorganic compounds, mainly chlorides (Robinson). The blister is thus apparently formed by drops of sweat emerging into the stratum corneum and represents, in essence, a retention sweat cyst. Regarding the mechanism of blister formation, Terék's explanation is the most acceptable: during a febrile state the skin is dry, the separating sweat evaporates already in the pores, the corneal cells here do not detach due to dryness, which is why the pores can become blocked; subsequently, during strong sweating, the sweat cannot exit onto the surface of the skin and therefore rushes between the plates of the stratum corneum. Thus, M. crystallina can be considered as an excretory anomaly of the sweat glands. Kreibich thinks that M. crystallina arises only in those cases where there is coagulation of the stratum corneum, which can be conditioned by the action of ultraviolet light, chemical factors, etc., including high body temperature. - M. crystallina is never accompanied by inflammatory phenomena, which is its main difference from other types of sweat rash described below. M. crystallina occurs mainly in children at an early age, rachitic children, as well as in persons with delicate skin. In some cases, the transparent blisters of M. crystallina become cloudy, and this cloudiness depends not on the penetration of leukocytes into the blisters, as happens with M. alba (see below), but due to the detachment of epithelial cells into the blisters. Mirolyubova distinguishes this variety of sweat rash under the name crystallina alba (in contrast to M. alba). - Diagnosis of M. crystallina usually presents no difficulties. Miliaria rubra (properly sudamina, eczema sudamen, impetigo miliaris) arises during profuse sweating, more often in men, in warm weather during profuse sweating in various febrile diseases, being in particular a constant and main symptom of the so-called sweat fever (febris miliaris, sudor anglicus), as well as in children during excessively warm keeping and rare bathing. In M. rubra, groups of small, the size of a millet grain to a pinhead, bright red, round nodules appear on the trunk, neck, and limbs. The rash is always accompanied by severe itching. M. rubra is distinguished by its instability, i.e., it intensifies during warm keeping of the patient and fades before the eyes upon cooling. In cases of prolonged existence of miliaria rubra, sometimes secondary eczematization occurs, especially upon localization in the axillary fossae, under the mammary glands, and on other contiguous areas of skin. The average duration of M. rubra is from 8 to 10 days. - Histologically: dilation of vessels, edema, and slight leukocytic infiltration in the papillary layer of the dermis; in the epidermis between the stratum corneum and granular layer a small blister is found, forming either according to the type of eczematous blister (as a result of interstitial inflammation of the epidermis) or according to the type of impetigo blister (due to rupture of individual cell layers). Robinson, Politzer, and Ziegler saw a connection between the blisters of M. rubra and the excretory ducts of sweat glands. The blisters of M. rubra, in contrast to the blisters in M. crystallina, do not represent retention sweat cysts, but are the consequence of an inflammatory process caused by excessively separating sweat; they contain a greater or lesser amount of leukocytes. Terék considers the presence of a special sensitivity of the skin to external irritations or special irritating properties of sweat to be a necessary condition for the occurrence of M. rubra. D'Arrieu, on the basis of research in his laboratory, considers M. rubra to be the consequence of diffuse autoinoculation by microbes due to maceration of the epidermis by sweat; he speaks not of M. rubra, but of impetigo miliaris. An absolutely interesting case is that of Mie-scher, in which widespread oidiomycosis clinically ran under the picture of M. rubra. - In differential diagnosis, one should mainly take into account papulo-vesicular eczema, as well as scarlet fever. The transparent blisters of M. rubra usually gradually become cloudy due to the increasing penetration of leukocytes into them. This stage of sweat rash is called M. alba. A special form of sweat rash is the so-called M. papulosa (syn.: lichen tropicus, scabies falsa, gale bedouine, prickly heat), which in essence represents a very intensely expressed variety of M. rubra. Most papular elements later turn into blisters, miliaria papulosa; it occurs in hot countries in summer, and it is interesting to note that the indigenous population of these countries never suffers from this form of sweat rash; it is almost exclusively the visitors who contract it. For the treatment of all types of sweat rash, indifferent powders (talc, zinc oxide), mixtures for shaking (Zinci oxyd., Talci veneti, Glycerini, Aq. plumbi aa 25,0 and others), baths with Zinc, sulfuric. (20,0–30,0 per bath), etc. are used.