Download 1. Scleredema

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B. Mucinoses
Definition, Pathogenesis
Mucinosis is a general term for diseases in which acid
mucopolysaccharide (mucin) deposits in the skin. The mucin,
produced by fibroblasts, consists of complex of mucopolysaccharides (glycosaminoglycans) and proteins. The main types of glycosaminoglycan are hyaluronic acid (hyaluronan), dermatan
sulfate, chondroitin sulfate and keratan sulfate. The mucin stains
positive with Alcian blue and colloidal iron, and metachromatic
with toluidine blue.
Abnormal deposition of mucin among collagen fibers results
in swelling and separation of those fibers and the edematous skin.
Mucin deposition is often induced by collagen disease, thyroid
dysfunction or tumor; however, the precise mechanism is
unknown. Mucinosis is classified by the location of deposition
and clinical features (Table 17.2).
Table 17.2 Classification of major cutaneous mucinoses.
Generalized mucinoses
Scleredema
Diffuse myxedema
Pretibial myxedema
Lichen myxedematosus
Reticular erythematous mucinoses
Localized mucinoses
Follicular mucinosis
Cutaneous focal mucinosis
1. Scleredema
Synonym: Scleredema adultorum
Stiffness occurs in the skin, especially of the face, neck, shoulders, upper back, and in some cases the upper extremities and
trunk (Fig. 17.5). The distal portions of the extremities are not
involved. The induration is non-pitting and hard. It is asymptomatic at the early stages; however, mild mobility impairment
appears gradually. Scleredema is often induced by acute infectious disease. The epidermis of the lesions thickens. Hyaluronic
acid and dermatan sulfate deposit among the dermal collagen
fibers (Fig. 17.6). Differentiation from diabetic scleredema
(described later) is important; when scleredema is suspected, diabetes should be tested for. Scleredema heals spontaneously in
several months to several years.
Clinical images are available in hardcopy only.
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Clinical images are available in hardcopy only.
2. Diffuse myxedema
It is mucoid edema (myxedema) on the entire body skin,
which often occurs when there is decreased thyroid activity. The
skin is cold, dry and white. When pinched, the skin is soft and no
marks are left (non-pitting edema). The disorder is characterized
by the facial features: the entire face is swollen, the nose widens,
and macroglossia and lip swelling are present. The scalp hair and
the hairs in the lateral one-third of each eyebrow become thin and
fragile.
3. Pretibial myxedema
The frontal tibiae and the dorsa of feet are most commonly
Fig. 17.5 Scleredema.
Marked hardening of the skin on the neck and
upper back.
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Metabolic Disorders
involved. Light pink to brownish plaques, subcutaneous induration, and nodules occur. Dilated follicles and hirsutism are present. The etiology is unknown. It occurs in 1% to 10 % of all
hyperthyroid cases. Ophthalmopathy is seen in almost all
patients.
4. Lichen myxedematosus
Synonyms: Scleromyxedema, Papular mucinosis
Soft, yellowish papules aggregate and coalesce on the axillary
fossae, dorsal hands and fingers, and extensor surfaces of forearms, presenting an orange-peel-like appearance. Hyalunic acid
deposition is present in the lesions. Endocrine function is usually
normal. Myeloma, diabetes, and liver dysfunction may occur.
Fig. 17.6 Histopathology of scleredema.
5. Reticular erythematous mucinosis
Reticular erythema occurs on sun-exposed areas of the trunk
(Fig. 17.7). It is characterized by glycosaminoglycan deposition
in the dermal upper layer.
Clinical images are available in hardcopy only.
6. Follicular mucinosis
Fig. 17.7 Reticular erythematous mucinosis.
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Papules of normal skin color to rose pink aggregate, coalescing mainly on the scalp and face and becoming elevated plaques
(Fig. 17.8). Alopecia often accompanies this. Pathologically,
edema and mucin deposition are seen in the outer root sheaths
and sebaceous glands. Vacuolization of follicles and lymphatic
infiltration also occur. Follicular mucinosis may occur primarily
or secondarily. Mycosis fungoides may develop as complications.
Clinical images are available in hardcopy only.
Fig. 17.8 Follicular mucinosis.
The skin lesion is accompanied by relatively
sharply demarcated, reddish infiltration of 3 cm
to 4 cm in diameter, and alopecia.
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