Table of Contents   This Chapter   All Chapters

MUCINOSES

The classification of cutaneous mucinoses, and the rationale for each different version, is a constant source of debate and is beyond the scope of this text. A tentative but clinically relevant approach is given in Table 11.8 (Figs 11.51 – 11.58).

    Some disorders in which mucin deposition occurs are discussed elsewhere; most of the remainder are rare (with the exception of digital myxoid cyst, which is common) but are briefly discussed here.

Reticulate erythematous mucinosis

Etiology and pathogenesis

This is an uncommon dermatosis, affecting women more often than men, usually in young adults. There are many similarities to LE, particularly the photosensitivity that is frequently reported; indeed, the two disorders may be associated, and some patients have other autoimmune diseases. However, internal involvement as seen in LE does not occur, and immunofluorescence of skin biopsies is negative. The degree of mucin deposition is greater than the small amounts seen in some cases of LE.

Fig. 11.51 Reticulate erythematous mucinosis. The upper back and V of the neck areas are the typical sites for lesions, which are typically rather non-specific erythematous papules or reticulate plaques. Most patients are female.

Fig. 11.52 Small, scattered lesions with the typical gray color, which can occur in small lesions of mucinosis; the patient also had deep granuloma annulare but no evidence of autoimmune endocrine or metabolic diseases (especially diabetes or thyroid disease), and no paraproteinemia, and did not wish further investigations. (Courtesy of Dr. L. Barco.)

Fig. 11.53 Lichen myxedematosus. (a) The typical form, having a sheet of discrete, small, skin-colored papules. (b) Nodular form. This is an unusual variant, not well served by the term lichen; it may be confused with simple edema or lymphedema, or with a soft nodule such as a lipoma, although this would be an unusual site. Some rather more cobblestoned lesions, more typical of this disease, are apparent further up the shin.

Fig. 11.54 Scleredema typically affects the upper trunk and causes a marked peau d’orange appearance; the dermis is expanded by mucin, but the follicles are tethered.

Fig. 11.55 Scleredema diabeticorum. The peau d’orange appearance can be exaggerated by pinching the skin, which also demonstrates a massive increase in dermal thickness. (See also Figs 12.18)

Fig. 11.56 A side view of the upper back in a patient with scleredema demonstrates the pitting of the skin that occurs after pressure (or squeezing, as in Figs 11.55. This is typically very slow to regain a normal contour, presumably due to the high viscosity of the mucinous infiltrate.

Fig. 11.57 (a) Digital myxoid (mucinous) cyst at a typical site on the dorsal aspect of the terminal phalanx of a finger. (b) Puncture of the cyst demonstrates extrusion of sticky, jelly-like, mucinous fluid.

Fig. 11.58 Digital myxoid cyst demonstrating the associated nail dystrophy that is a common feature. This is due to compression of the nail matrix within the proximal nail fold, therefore causing a groove that runs along the length of the nail.

Clinical features

The disorder usually occurs on the chest and V region of the neck, and consists of patchy or reticulate-patterned lesions, which are often just palpable (Fig.11.51). Exacerbation due to sunlight, and occurrence confined to the summer months, are common findings, but routine phototests and provocation tests are negative.

Differential diagnosis

The main differential is from LE or polymorphic light eruption.

Treatment

There is usually a dramatic response to oral hydroxychloroquine or mepacrine.

Generalized lichen myxedematosus (scleromyxedema)

Etiology and pathogenesis

Lichen myxedematosus (Fig. 11.53a) is a rare disorder that consists of extensive papular lesions, or a more diffuse sclerodermoid pattern. It is usually associated with benign monoclonal gammopathy, usually IgG  type, although the titer does not appear to correlate with disease severity. Histologically, there is extensive deposition of mucin throughout the dermis.

Clinical features

Lesions are papular and waxy in appearance, but merge into confluent, firm, shiny, infiltrated plaques that may become generalized and resemble scleroderma. Facial features become coarsened, and inability to open the mouth adequately may be a significant problem. Sclerodactyly and inability to extend the fingers are frequent, but the telangiectasia of systemic sclerosis is not seen, and there is always some degree of a papular component in scleromyxedema. The Koebner phenomenon has been reported in scleromyxedema.

Differential diagnosis

The main differential diagnoses in established cases are systemic sclerosis (Ch. 13) and scleredema (discussed later). The papular lesions may suggest micropapular sarcoidosis or the diffuse form of GA, but these generally affect the trunk predominantly. Some histiocytoses, or rare disorders such as lipoid proteinosis, may also need to be considered on clinical grounds.

Treatment

The localized versions may regress spontaneously, and even generalized scleromyxedema may improve without any intervention. In more severe cases, treatment of the underlying gammopathy, usually with melphalan, may lead to improvement in the cutaneous features. A dramatic response to intravenous immunoglobulin has recently been reported.

Localized forms of lichen myxedematosus

All forms (Fig. 11.53b, Table 11.8) are uncommon or rare. Lesions are off-white or grayish colored, often translucent, papules, sometimes with a lichenoid appearance. Some forms are defined by the specific site affected, as is apparent from the nomenclature. Biopsy confirms mucin deposition.

Fig. 11.59 Macular amyloid typically occurs as a pigmented region with a rather rippled appearance, as shown on the upper back (a) and arm (b). It seems to be disproportionately common in Asian skin, when it may be very extensive. (c) In at least some individuals, it is probably just a response to chronic rubbing, as was almost certainly the case in this patient with a very localized area corresponding to the position achieved by rubbing the left upper back with the (dominant) right hand.

Fig. 11.60 Nodular amyloid usually presents as one or a few brownish nodules (a), which may resemble granulomatous nodules such as sarcoidosis or granuloma faciale (really a type of vasculitis; discussed in Ch. 14). Some lesions become quite large (b). Note that some localized skin tumors may also generate large amounts of amyloid material, usually detected only when they are examined histologically.

Fig. 11.61 Systemic amyloidosis. (a) Fragility of cutaneous vasculature is typical, and extravasation of erythrocytes may occur in poorly supported skin after coughing or a Valsalva maneuver. In this case, the linear purpura was probably due to pressure from clothing or minor scratches. Extensive eyelid bruising may also occur. (b) Macroglossia is a useful diagnostic feature in systemic amyloidosis.

Scleredema

Etiology and pathogenesis

This disorder may occur after streptococcal or viral upper respiratory infections (scleredema of Buschke), and also occurs in association with chronic diabetes mellitus, especially in those patients with insulin resistance. It may also occur in association with myeloma or monoclonal gammopathy. By contrast with scleromyxedema, there is less mucin deposition and abnormal thickening of collagen.

Clinical features

The clinical appearance is striking, especially in the postinfective patients in whom onset is often quite rapid. The skin of the upper back and nape of neck becomes indurated and tethered, with a peau d’orange appearance and erythema (Fig 11.54 – 11.56). It may extend to other areas, such as the face and proximal limbs.

Differential diagnosis

This includes systemic sclerosis and scleromyxedema.

Treatment

Treatments such as antibiotics in the infective cases, corticosteroids, immunosuppressive agents, and penicillamine all appear to be equally ineffective.

Digital myxoid cyst

This is a common disorder, which is most commonly seen on fingers but can occur on toes. Some cases appear to occur following local injury, but most are probably caused by extrusion of fluid from the adjacent distal interphalangeal joint (which often has changes of osteoarthritis). The fluid tracks distally beneath the skin of the dorsum of the finger toward the proximal nail fold, where it may intermittently discharge or may compress the nail matrix, thereby causing distortion of the nail plate (Figs 11.57 and 11.58); see also Ch.29). Treatment is by surgery, cryotherapy, or intralesional steroid, but recurrence is frequent unless the proximal source of fluid can be obliterated.

     This lesion is generally readily diagnosed if the practitioner has seen a case previously. The referral diagnosis may include warts, various tumors and cysts, foreign body reactions, and traumatic or non-specific nail dystrophies.

Previous

Next

White/Cox: Diseases of the Skin, 2ed.(c) 2006, Elsevier Inc. All rights reserved.