Chapter 651 Diseases of the Dermis
Keloid
Etiology/Pathogenesis
Keloids are usually induced by trauma and commonly follow ear piercing, burns, scalds, and surgical procedures. Certain individuals are predisposed to keloid formation; a familial tendency (recessive or dominant inheritance) or the presence of foreign material in the wound may have a pathogenic role. Keloids are a rare feature of Ehlers-Danlos syndrome, Rubinstein-Taybi syndrome, and pachydermoperiostosis. Keloids result from an abnormal fibrous wound healing response in which tissue repair and regeneration-regulation control mechanisms are lost. Collagen production is 20 times that seen in normal scars and the type I/type III collagen ratio is abnormally high. In keloids, tissue values of tumor growth factor-β (TGF-β) and platelet-derived growth factor (PDGF) are elevated; fibroblasts are more sensitive to their effects, and their degradation rate is decreased.
Clinical Manifestations
A keloid is a sharply demarcated, benign, dense growth of connective tissue that forms in the dermis after trauma. The lesions are firm, raised, pink, and rubbery; they may be tender or pruritic. Sites of predilection are the face, earlobes (Fig. 651-1), neck, shoulders, upper trunk, sternum, and lower legs. In both keloids and hypertrophic scars, new collagen forms over a much longer period than in wounds that heal normally.
Differential Diagnosis
Keloids should be differentiated from hypertrophic scars, which remain confined to the site of injury and gradually involute over time.
Treatment
Young keloids may diminish in size if injected intralesionally at 4-wk intervals with triamcinolone suspension (10-40 mg/mL). At times, a more concentrated suspension is required. Large or old keloids may require surgical excision followed by intralesional injections of corticosteroid. The risk of recurrence at the same site argues against surgical excision alone, although ear lobe keloids respond well to surgical excision, pressure dressings, and intralesional steroids. Placement of topical silicon gel sheeting over the keloid for several hours per day for several weeks may help in some patients.
Striae Cutis Distensae (Stretch Marks)
Etiology/Pathogenesis
Striae formation is common in adolescence. The most frequent causes are rapid growth, pregnancy, obesity, Cushing disease, and prolonged corticosteroid therapy. The pathogenesis is unknown, but the occurrence of alterations in elastic fibers is thought to be the primary process.
Clinical Manifestations
These thinned, depressed, erythematous bands of atrophic skin eventually become silvery, opalescent, and smooth. They occur most frequently in areas that have been subject to distention, such as the lower back (Fig. 651-2), buttocks, thighs, breasts, abdomen, and shoulders.
Corticosteroid-Induced Atrophy
Etiology/Pathogenesis
Both topical and systemic corticosteroid treatment can result in cutaneous atrophy. This is particularly common when a potent or superpotent topical corticosteroid is applied under occlusion or to an intertriginous area for a prolonged period. Keratinocyte growth is decreased, but epidermal maturation is accelerated, resulting in a thinning of the epidermis and stratum corneum. Fibroblast growth and function are also decreased, leading to the dermal changes. The mechanism involves inhibition of synthesis of collagen type I, noncollagenous proteins, and total protein content of the skin, along with progressive reduction of dermal proteoglycans and glycosaminoglycans.
Clinical Manifestations
Affected skin is thin, fragile, smooth, and semitransparent, with telangiectasias and loss of normal skin markings.
Histology
Histopathologically, one sees thinning of the epidermis. Spaces between dermal collagen and elastic fibers are small, producing a more compact but thin dermis.
Granuloma Annulare
Etiology/Pathogenesis
The cause of granuloma annulare is unknown. Some cases of granuloma annulare, particularly the generalized form, may be associated with diabetes mellitus or with anterior uveitis. However, most cases are seen in healthy children.
Clinical Manifestations
This common dermatosis occurs predominantly in children and young adults. Affected children are usually healthy. Typical lesions begin as firm, smooth, erythematous papules. They gradually enlarge to form annular plaques with a papular border and a normal, slightly atrophic or discolored central area up to several centimeters in size. Lesions may occur anywhere on the body, but mucous membranes are spared. Favored sites include the dorsum of the hands (Fig. 651-3) and feet. The disseminated papular form is rare in children. Subcutaneous granuloma annulare tends to develop on the scalp and limbs, particularly in the pretibial area. These lesions are firm, usually nontender, skin-colored nodules. Perforating granuloma annulare is characterized by the development of a yellowish center in some of the superficial papular lesions as a result of transepidermal elimination of altered collagen.
Differential Diagnosis
Annular lesions are often mistaken for tinea corporis because of the elevated advancing border. They differ in that they are not scaly. Papular lesions, another variant, may simulate rheumatoid nodules, particularly when grouped on the fingers and elbows.
Histology
The lesion of granuloma annulare consists of a granuloma with a central area of necrotic collagen; mucin deposition; and a peripheral palisading infiltrate of lymphocytes, histiocytes, and foreign body giant cells. The pattern resembles that of necrobiosis lipoidica and rheumatoid nodule, but subtle histologic differences usually permit differentiation.
Treatment
The eruption persists for months to years, but spontaneous resolution without residual change is usual; 50% of lesions clear within 2 years. Application of a potent or superpotent topical corticosteroid preparation or intralesional injections (5-10 mg/mL) of corticosteroid may hasten involution, but nonintervention is usual.
Necrobiosis Lipoidica
Etiology/Pathogenesis
The cause of necrobiosis lipoidica is unknown, but 50-75% of patients have diabetes mellitus; necrobiosis lipoidica occurs in 0.3% of all diabetic patients.
Clinical Manifestations
This disorder manifests as erythematous papules that evolve into irregularly shaped, sharply demarcated, yellow, sclerotic plaques with central telangiectasia and a violaceous border. Scaling, crusting, and ulceration are frequent. Lesions develop most commonly on the shins (Fig. 651-4). Slow extension of a given lesion over the years is usual, but long periods of quiescence or complete healing with scarring may occur.
Histology
Poorly defined areas of necrobiotic collagen are seen throughout, but primarily low in the dermis, associated with mucin deposition. Surrounding the necrobiotic, disordered areas of collagen is a palisading lymphohistiocytic granulomatous infiltrate. Some lesions are more characteristically granulomatous, with limited necrobiosis of collagen.
Differential Diagnosis
Necrobiosis lipoidica must be differentiated clinically from xanthomas, morphea, granuloma annulare, erythema nodosum, and pretibial myxedema.
Lichen Sclerosus
Clinical Manifestations
Lichen sclerosus manifests initially as shiny, indurated, ivory-colored papules, often with a violaceous halo. The surface shows prominent dilated pilosebaceous or sweat duct orifices that often contain yellow or brown plugs. The papules coalesce to form irregular plaques of variable size, which may develop hemorrhagic bullae in their margins. In the later stages, atrophy results in a depressed plaque with a wrinkled surface. This disorder occurs more commonly in girls than in boys. Sites of predilection in girls are the vulvar (Fig. 651-5), perianal, and perineal skin. Extensive involvement may produce a sclerotic, atrophic plaque of hourglass configuration; shrinkage of the labia and stenosis of the introitus may result. Vaginal discharge precedes vulvar lesions in approximately 20% of patients. In boys, the prepuce and glans penis are often involved, usually in association with phimosis; most boys with the disorder were not circumcised early in life. Sites elsewhere on the body that are most commonly involved include the upper trunk, the neck, the axillae, the flexor surfaces of wrists, and the areas around the umbilicus and the eyes. Pruritus may be severe.
Differential Diagnosis
In children, lichen sclerosus is most frequently confused with focal morphea (Chapter 154), with which it may coexist. In the genital area, it may be mistakenly attributed to sexual abuse.
Histology
Biopsy is diagnostic, revealing hyperkeratosis with follicular plugging, hydropic degeneration of basal cells, a bandlike dermal lymphocytic infiltrate, homogenized collagen, and thinned elastic fibers in the upper dermis.
Treatment
Vulvar lichen sclerosus in childhood usually improves with puberty but does not usually resolve, and symptoms can recur throughout life. Long-term observation for the development of squamous cell carcinoma is necessary. Superpotent topical corticosteroids provide relief from pruritus and produce clearing of lesions, including those in the genital area. Topical tacrolimus and pimecrolimus have also been used. It is not known how response to treatment affects long-term cancer risk.
Morphea
Etiology/Pathogenesis
Morphea is a sclerosing condition of the dermis and subcutaneous tissue of unknown etiology.
Clinical Manifestations
Morphea is characterized by solitary, multiple or linear circumscribed areas of erythema that evolve into indurated, sclerotic, atrophic plaques (Fig. 651-6), later healing, or “burning out” with pigment change. It is seen more commonly in females. The most common types of morphea are plaque and linear. Morphea can affect any area of skin. When confined to the frontal scalp, forehead, and midface in a linear band, it is referred to as en coup de sabre. When located on one side of the face, it is called progressive hemifacial atrophy. These forms of morphea carry a poorer prognosis because of the associated underlying musculoskeletal atrophy that can be cosmetically disfiguring. Linear morphea over a joint may lead to restriction of mobility (Fig. 651-7). Pansclerotic morphea is a rare severe disabling variant.
Differential Diagnosis
The differential diagnosis of morphea includes granuloma annulare, necrobiosis lipoidica, lichen sclerosis, and late-stage Lyme disease (acrodermatitis chronica atrophicans).
Treatment
Morphea tends to persist, with gradual outward expansion on the skin for 3-5 yr until spontaneous cessation of the inflammatory phase occurs. Topical calcipotriene alone or in combination with high- to super-potency topical steroids or topical tacrolimus have been used for less severe disease. For the various forms of linear morphea and for severe plaque morphea, ultraviolet A-1 (UVA-1) phototherapy, methotrexate 0.3-0.5 mg/kg/week, and glucocorticosteroids 1 mg/kg/day may halt progression and help shorten the disease course. There are no comparison studies to suggest which therapy is optimal. Physical therapy is needed in linear morphea over a joint to maintain mobility. Significant postinflammatory pigment alteration may persist for years.
Scleredema (Scleredema Adultorum, Scleredema of Buschke)
Etiology/Pathogenesis
The cause of scleredema is unknown. There are 3 types. Type I (55% of cases) is preceded by a febrile illness. Type 2 (25%) is associated with paraproteinemias, including multiple myeloma. Type 3 (20%) is seen in diabetes mellitus.
Clinical Manifestations
Fifty percent of patient with scleredema are younger than 20 yr and almost always have type 1. Onset of type 1 is sudden, with brawny edema of the face and neck that spreads rapidly to involve the thorax and arms in a sweater distribution; the abdomen and legs are usually spared. The face acquires a waxy, masklike appearance. The involved areas feel indurated and woody, are nonpitting, and are not sharply demarcated from normal skin. The overlying skin is normal in color and is not atrophic.
Onset in patients with type 2 and type 3 scleredema may occur insidiously. Systemic involvement, which is uncommon and usually associated with types 2 and 3, is marked by thickening of the tongue; dysarthria; dysphagia; restriction of eye and joint movements; and pleural, pericardial, and peritoneal effusions. Electrocardiographic changes may also be observed. Laboratory data are not helpful.
Differential Diagnosis
Scleredema must be differentiated from scleroderma (Chapter 154), morphea, myxedema, trichinosis, dermatomyositis, sclerema neonatorum, and subcutaneous fat necrosis.
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