Follicular mucinosis

The basis of follicular mucinosis is degenerative changes in the hair follicle and sebaceous glands with the destruction of their structure and the deposition of glycosaminoglycans (mucin). Reticular erythematous mucinosis (syn.: REM syndrome) was first described by L. Lischka and D. Ortheberger (1972), then by K. Steigleder et al. (1974).

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Causes follicular mucinosis

The causes and pathogenesis of follicular mucinosis have not yet been fully established. The causes of disturbances in the chemistry and structure of the main substance of connective tissue are unclear.

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Risk factors

Triggering factors can be viral, bacterial infections, disorders of the endocrine and immune systems, and pathologies of internal organs.

Under the influence of causal factors, there is a local disruption in the synthesis of the main substance of connective tissue and collagen by fibroblasts with the formation of mucin.

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Pathogenesis

The disease is based on a special type of necrobiotic changes in the epithelium of hair follicles caused by the appearance of a mucinous substance in it. The cause of the disease is unknown. H. Wolff et al. (1978) consider follicular mucinosis as a type of histological reaction common to a wide variety of unrelated irritants and reflecting disturbances in intraepithelial metabolism. According to E. J. Grussendof-Conen et al. (1984), a significant pathogenetic factor is the disturbance in the processes of differentiation of the sebaceous glands.

Histopathology

Degenerative changes in hair follicles and sebaceous glands are observed with the formation of cystic cavities filled with homogeneous masses (mucin) rich in glycosaminoglycans. Sometimes mucin is not detected. In the dermis, an infiltrate is observed consisting of lymphocytes and histiocytes, sometimes with the presence of eosinophils, mast and giant cells.

Degenerative changes in follicles in these forms are similar, the difference is that in the symptomatic variant other characteristic histological signs of the underlying disease also appear. In addition, in symptomatic (secondary) mucinosis associated with mycosis fungoides, the inflammatory infiltrate consists of cells characteristic of mycosis fungoides with Potrier microabscesses in the epidermis.

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Pathomorphology

The epidermis is unchanged, only occasionally are there elongation of epidermal outgrowths, hyperkeratosis and focal spongiosis in the basal layer. In the upper third of the dermis, less often in its deep sections, perivascular and perifollicular infiltrates of a lymphocytic nature with an admixture of macrophages and individual tissue basophils are found. Dilation of blood vessels and edema of the upper sections of the dermis are noted, where glycosaminoglycans such as hyaluronic acid are found. The perivascular lymphocytic infiltrate characteristic of REM syndrome and accumulations of a mucus-like substance between collagen fibers make it similar to cutaneous mucinosis.

The pathomorphology of the skin in primary and secondary mucinosis is identical. In the epithelial sheaths and secretory sections of the sebaceous glands, inter- and intracellular edema occurs at the beginning of the process, leading to rupture of desmosomes and loss of communication between cells. Later, vesicles and cyst-like cavities appear at the site of spongiosis. Epithelial cells with pycnotic nuclei acquire a stellate appearance. Here, weakly basophilic masses are found that do not stain red with mucicarmine, but give metachromasia when stained with toluidine blue. Metachromasia is only partially removed by hyaluronidase, which indicates the presence of sulfated glycosaminoglycans in addition to hyaluronic acid. Hyper- and parakeratosis are noted in the funnels of hair follicles; hair is damaged or absent. Around the follicles and sebaceous glands there are always inflammatory infiltrates, which consist mainly of lymphocytes and histiocytes, sometimes with an admixture of eosinophilic granulocytes, tissue basophils and giant cells. Electron microscopic examination reveals a disorder of sebaceous gland secretion: an increase in the volume of secretory cells and secretory vacuoles, as well as the glycogen content in secretory cells. They contain unusual electron-dense material, as a result of which they acquire a spotty appearance. All cellular elements participating in the pathological process have morphological signs of undifferentiated sebocytes.

In reticular erythematous mucinosis, mucin deposition and moderate mononuclear infiltration are found predominantly around vessels and hair follicles. Based on morphological and electron microscopic studies, DV Stevanovic (1980) concluded that plaque follicular mucinosis and REM syndrome are the same condition.

Symptoms follicular mucinosis

In follicular mucinosis, a characteristic change in the root sheath of the hair follicle is observed, in which its cells are transformed into a mucinous-mucous mass, which leads to the death of the hair follicle and subsequent alopecia. There are two types of follicular mucinosis: primary (or idiopathic, mucophanerosis), spontaneously regressing, and secondary, usually associated with lymphoproliferative diseases (mycosis fungoides, lymphomas) and other, more often systemic, skin diseases. The rash is represented by grouped follicular papules, less often infiltrated, sometimes tuberous plaques. Idiopathic follicular mucinosis GW Korting et al. (1961) consider a special form of eczematous reaction. M. Hagedorn (1979), based on the frequent combination of follicular mucinosis with malignant lymphoma, classifies this dermatosis as a paraneoplasia.

The rash is represented by grouped follicular papules, less often by yellowish-red infiltrated plaques. An erythrodermic variant has been described. It is most often localized on the scalp, neck, eyebrow area, less often on the trunk and limbs. Hair loss is observed, including vellus hair, which can lead to total alopecia. In children, the disease manifests itself in the form of isolated hyperkeratotic follicular papular elements the size of a pinhead, scattered or grouped on limited areas of the skin. When localized on the face, especially in the eyebrow area, there may be changes resembling leprosy. Primary mucinosis, as a rule, spontaneously regresses, which occurs earlier if the rash is less widespread. The presence of persistent foci with increased infiltration and itching in older people requires the exclusion of lymphoma.

Follicular mucinosis occurs at any age, but most often between the ages of 20 and 50. Men are more likely to get sick than women.

Clinically, two forms of the disease are distinguished: follicular-papular and plaque, or tumor-plaque. The skin-pathological process is often located on the face, scalp, trunk and limbs. The morphological elements of the rash in the first form are numerous small (2-3 mm) follicular nodules of a pinkish-bluish color, dense consistency, often with pronounced keratosis. The nodules tend to group together. Often the process takes on a disseminated character, and the rash resembles goose bumps. Most patients experience itching of varying degrees of severity. Over time, this form can become plaque, or tumor-plaque.

The plaque form of follicular mucinosis develops in almost 40-50% of patients, and then the clinical picture resembles mycosis fungoides or reticulosarcoma of the skin. One or more sharply demarcated infiltrated plaques from 2 to 5 cm in diameter appear. Plaques are usually flat, rise above the level of the surrounding skin, with clear boundaries, their surface is sometimes covered with small scales, dilated openings of hair follicles filled with horny masses are often visible. Plaques have a dense consistency. Severe itching of the skin is noted. As a result of the fusion of plaques and their further growth, tumor-plaque foci appear, which can undergo disintegration with the formation of painful ulcers. Papules, plaques and tumor-like elements can be observed simultaneously in one patient. Half of the patients experience hair loss, up to total alopecia.

Reticulated erythematous mucinosis (REM syndrome) clinically manifests itself as erythematous patches of irregular outline on the upper chest, neck and abdomen.

The course of the disease is long and recurrent.

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Forms

A distinction is made between primary (idiopathic) mucinosis, which develops without previous skin diseases, and secondary (symptomatic) mucinosis, which is observed in combination with mycosis fungoides, skin reticulosis, Hodgkin's disease, skin leukemia and, as an exception, chronic inflammatory dermatoses (neurodermatitis, lichen planus, lupus erythematosus, etc.).

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Differential diagnosis

Differential diagnosis includes parapsoriasis (especially plaque), nummular eczema, mycosis fungoides, reticulosis of the skin, keratosis pilaris, Devergie's red lichen pilaris, sarcoidosis, seborrheic eczema, Lassuer-Little syndrome. It is not always easy to differentiate primary and secondary mucinosis.

Treatment follicular mucinosis

In the follicular-nodular form, corticosteroids are used (40-50 mg of prednisolone per day). In the tumor-plaque form, the same measures are taken as in the case of skin lymphomas. Corticosteroids are prescribed externally.