Mucinoses

• Symmetric diffuse induration of the skin, usually limited to the upper back and posterior neck, that may require palpation to be appreciated; a peau d'orange appearance may be present with prominent follicular orifices, and occasionally there is blanching erythema in the sites of involvement (Fig. 38.1).

• While scleredema is often asymptomatic, some patients may complain of tightness or decreased range-of-motion; occasionally there is also involvement of the face and upper extremities and rarely, the muscles, eyes, or heart.

• The three major types have different associations: type I – preceding streptococcal infections; type II – monoclonal gammopathy; and type III – diabetes mellitus, with men representing the majority of patients.

• DDx: systemic sclerosis (diffuse form), scleromyxedema, and other sclerodermoid disorders (see Table 35.4); occasionally, cellulitis if erythema is present.

• Rx: sometimes there is spontaneous resolution, especially with type I disease, but control of underlying diabetes mellitus does not lead to improvement; anecdotal therapies include phototherapy (e.g. UVA1, PUVA) and electron beam therapy.

• A spectrum of clinical findings that varies from multiple linear arrays of firm, 2- to 3-mm, waxy, skin-colored papules (Fig. 38.2) to diffuse induration of the skin with thickened folds, including leonine facies (Fig. 38.3; Table 38.1); involvement is symmetric and often widespread.

• Associated with an underlying monoclonal gammopathy; in addition to skin stiffness, there can be decreased range-of-motion of joints and contractures as well as myositis, peripheral neuropathy, and encephalopathy (dermato-neuro syndrome).

• DDx: systemic sclerosis, scleredema; if primarily papules, primary systemic amyloidosis, lipoid proteinosis, and especially the various types of skin-limited (localized) mucinoses, e.g. acral persistent papular mucinosis, self-healing cutaneous mucinosis, the discrete papular form of lichen myxedematosus.

• Rx: similar to that of multiple myeloma (see primary systemic amyloidosis, Chapter 39), systemic retinoids, PUVA, UVA1.

• In the vast majority of patients, associated with hyperthyroidism, primarily due to Graves' disease, an autoimmune disorder with circulating anti-thyroid-stimulating hormone receptor autoantibodies; lesions may appear following treatment of the thyroid disease, i.e. when the patient is euthyroid or hypothyroid.

• Favors the shins but can involve the foot and presents as indurated, waxy nodules or plaques that vary from skin-colored to red-brown (Fig. 38.4); there can be a prominence of follicular openings (peau d'orange appearance) and occasionally elephantiasis develops.

• Additional clinical findings include exophthalmos, goiter, and thyroid acropachy.

• DDx: obesity-associated lymphedematous mucinosis (no history of hyperthyroidism), lymphedema, lipedema, lichen amyloidosis.

• Rx: although lesions may clear spontaneously over a period of several years, treatment of the underlying thyroid disease usually has no effect; anecdotal therapies include topical and intralesional CS, pneumatic compression, surgical shave removal, octreotide.

• As a result of profound hypothyroidism, the skin is diffusely dry, cool, and pale, with a waxy appearance; the hair and nails can be brittle, leading to a diffuse non-scarring alopecia of the scalp and alopecia of the lateral eyebrows.

• Additional mucocutaneous findings in­clude eczema craquelé, acquired ichthyosis, carotenoderma, and a puffiness of the hands and the face, including the eyelids; the tongue may be enlarged.

• In the congenital form, mental retardation, dwarfism, poor muscle tone, constipation, and somnolence are characteristic findings.

• Because the most common underlying disease in adults is Hashimoto's thyroiditis, women are more commonly affected; in addition to the skin changes outlined above, patients may gain weight, have cold intolerance and constipation, feel sluggish, and can occasionally develop cutaneous xanthomas.

• Rx: thyroid replacement.

• Acute eruption of multiple firm papules and nodules favoring the face (especially the forehead and periorbital region), scalp, and periarticular areas.

• No underlying disorder and characterized by spontaneous resolution over months to years.

• Persistent erythematous papules of the central chest and central back that can form a net-like pattern and/or coalesce into plaques (Fig. 38.5); may be photo-aggravated.

• Overlaps with lupus erythematosus (LE) tumidus, Jessner's benign lymphocytic infiltrate (minimal to no dermal mucin), and papulonodular mucinosis (see below).

• Rx: topical or intralesional CS, antimalarials, e.g. hydroxychloroquine, chloroquine, sunscreens.

• Occurs in the setting of autoimmune connective tissue diseases, with LE >> dermatomyositis or systemic sclerosis; ~75% of patients with LE who develop these lesions have systemic involvement.

• Skin-colored to erythematous papules and nodules that may require side-lighting to appreciate; favors the back, V of the chest and upper extremities (Fig. 38.6).

• Overlaps with LE tumidus, reticular erythematous mucinosis, and Jessner's benign lymphocytic infiltrate (minimal to no dermal mucin).

• Rx: antimalarials, e.g. hydroxychloroquine, chloroquine, topical or intralesional CS, sunscreens.

• In contrast to the other disorders in this chapter, here the mucin is deposited within the epithelium of hair follicles rather than in the dermis.

• In the primary form, there are pink to violet-brown plaques, primarily in the head and neck region, that have associated alopecia and sometimes scale (Fig. 38.7A); in some patients, there are grouped follicular papules (Fig. 38.7B), and in patients with darkly pigmented skin, lesions may be hypopigmented.

• The primary form most commonly occurs in children and young adults and represents a benign, self-limited disease; in older adults, especially when the lesions are more widespread and persistent, the possibility of coexisting mycosis fungoides needs to be considered.

• In addition to the characteristic histologic finding of mucin deposition within the follicular epithelium, it is important to comment on the presence or absence of atypical lymphocytes.

• DDx: cutaneous LE, tinea faciei or capitis, facial discoid dermatosis, various forms of dermatitis; if diagnosed histologically, consider an incidental finding (e.g. associated with atopic dermatitis).

• Rx: for primary, observation until spontaneous resolution, topical or intralesional CS, antimalarials; if associated with mycosis fungoides, treat the latter (see Chapter 98).