Seborrheic dermatitis This term refers to a scaly, crusting, and erythematous eruption that is most common in infancy (ages 2-12 weeks), where it tends to favor the scalp, diaper area, and intertriginous folds. Figure 12-1 is an illustration of the process in the scalp where it is often referred to as cradle cap.

Figure 12-2 illustrates severe involvement in the eyebrows, a common area of involvement. A subset of infants with seborrheic dermatitis will go on to develop atopic dermatitis and it sometimes may be difficult to differentiate between these two conditions.

Seborrheic dermatitis Figure 12-3 shows very severe facial and scalp involvement. Some basic principles are that the lesions of seborrheic dermatitis are usually well circumscribed, do not itch, and localize toward the face, scalp, and intertriginous areas. The greasy red-orange scaliness of seborrheic dermatitis is somewhat helpful in differentiating this disorder from atopic dermatitis.

Figure 12-4 shows a more extensive process that is nearly generalized, dry, and scaly. Seborrheic dermatitis has its onset early in infancy and usually resolves by 1 year of age; atopic dermatitis tends to be more persistent.

Seborrheic dermatitis The cause of this very common condition remains unknown. Although it favors areas with an increased number of sebaceous glands, there is no evidence that seborrheic dermatitis is a disease of sebaceous glands or is related to excessive sebum production.

Some studies have suggested that the lipid composition of sebum in seborrheic dermatitis may be abnormal. Bacteria and yeasts are often present in areas of involvement, but neither Candida albicans nor Pityrosporum ovale has been shown to be an etiologic agent.

Seborrheic dermatitis Seborrheic dermatitis, common during infancy, is relatively unusual during later childhood. It resurfaces as a problem during adolescence and then seems to become progressively more common through adult life. The adolescent variant primarily involves the scalp, forehead, tarsal margins of the eyelids (blepharitis), ears, and nasolabial folds. Seborrheic dermatitis is easily controlled but not curable. Treatment may consist of the topical application of ketoconazole cream or a mild topical steroid. The frequent use of tar shampoos is particularly helpful in the control of seborrheic dermatitis of the scalp.

During puberty and in adulthood, seborrheic dermatitis occurs not only on the scalp and face but also on the chest, on the back, and in intertriginous spaces such as the axillae (illustrated in Fig. 12-8), inframammary areas, groin, and intergluteal folds. Lesions on the chest and back are described as petaloid, that is, flat and demarcated like petals; in intertriginous spaces, the appearance can be glistening red.

Tinea amiantacea This term requires etymological explanation. The tinea does not mean superficial fungal infection but rather a condition that resembles a superficial mycosis. Amiantacea means asbestos-like. The combination describes a superficial scaly process that recalls the crumbling exfoliation of asbestos. Such an appearance occurs in the scalp in some cases of seborrheic dermatitis, psoriasis, tinea capitis, and pityriasis sicca (dandruff). The term is discarded as soon as a better diagnosis is made.

Psoriasis More than one-quarter of all individuals with psoriasis develop their disease during childhood or adolescence. The degree of involvement is extremely variable; some children develop only a few localized plaques, while others suffer from generalized skin disease and severe arthritis.

Pictured in Figs. 12-10 and 12-11 are the typical lesions of psoriasis; the plaques have a red-to-orange hue, are scaly, and are sharply demarcated from the surrounding skin.

Psoriasis The distinctive character of the scale is appreciated in these figures. The scale is usually described as silvery or micaceous (resembling the mineral mica). When the scale is removed, pinpoint areas of bleeding (Auspitz sign) are uncovered.

Each lesion of psoriasis represents an area of rapid epidermal cell turnover. The thickening of the involved epidermis and the overlying parakeratosis translate into the raised and scaly appearance of the involved skin.

Psoriasis The symmetrical involvement of the knees is a common pattern; elbows and buttocks are other favored locations for plaques like these.

A typical sharply demarcated plaque with micaceous scale on the knee is shown in Fig. 12-14 and on the elbow in Fig.12-15.

Psoriasis In Fig. 12-16 and 12-17, we see plaques of dense adherent scale in the scalp. Circumscribed areas of micaceous scale in the scalp are a common presenting sign of psoriasis. This disorder can usually be differentiated from tinea capitis by the character of the scale, the sharp demarcation, and, usually, the absence of hair loss.

Lesions in the scalp tend to cause pruritus. When treating the scalp, it is important to decrease the scale so that the topical medications become more effective. Preparations containing salicylic acid, a keratolytic, are especially useful for the treatment of scalp psoriasis.

Psoriasis In Fig. 12-18, we see typical involvement of the glabrous skin of the neck, with extension into the scalp. This is a common location, and, in some cases, psoriasis may develop over a persistent nevus simplex (stork bite) in that area.

Unilateral, or, more commonly, symmetrical involvement of the skin around the eyes may occur in psoriasis. The involvement of the medial aspect, as shown in Fig. 12-19, is particularly common.

Psoriasis Figures 12-20,12-21,12-22,12-23 show the erythema, scaling, and thickening of portions of the palms and soles that are very common in both children and adults with psoriasis. Therapy of psoriasis is based on the skillful use, either alone or in combination, of a number of therapeutic agents.

The most common topical treatments include topical steroids, tars, keratolytics, ultraviolet light, and topical calcipotriol and tazarotene in older patients. Children with simple plaque psoriasis can sometimes be managed with short-contact anthralin preparations.

Psoriasis When topical steroids are used, it is important to employ the least potent preparation that is effective and to avoid the use of fluorinated steroids on the face and in intertriginous areas. Careful exposure to sunlight during the summer months and artificial ultraviolet light at other times is enormously beneficial in selected patients with extensive involvement.

Thickening and fissuring of the palms or soles can become extremely painful. Patients with severe involvement like this, and those with severe generalized involvement may sometimes require systemic therapy. Treatments include methotrexate, acitretin, and biologic agents.

Psoriasis In Fig. 12-24, the lesions consist of numerous papules, each covered with the typical silvery scales of psoriasis. This form of the condition, termed guttate psoriasis, is more common in childhood and may have an explosive onset. There is often a history of an antecedent upper-respiratory infection, and streptococcal disease is of particular importance in triggering this eruption. The use of oral antibiotics that are effective against Streptococcus sometimes hastens the resolution of guttate psoriasis. The use of mild topical corticosteroids is of benefit.

Rarely, patients develop psoriasis in a linear distribution. In some cases, this is a simple result of Koebnerization, the development of lesions in areas that are being scratched or traumatized in some other way. In other cases, the development of linear psoriasis follows the lines of Blaschko, and may indicate a somatic mutation in the skin.

Psoriasis Pictured here are two representations of psoriasis in the diaper area. In Fig.12-26, the entire diaper area is involved with a sharply demarcated erythematous scaling eruption. Figure 12-27 shows the sharply demarcated eruption with minimal involvement of the scrotum but involvement of the prepuce of the penis. When onset of the disease occurs during infancy, this is a very common area of involvement.

It is postulated that the repeated irritation in this area constitutes a type of Koebner phenomenon. Scales are less in evidence in Fig. 12-26 because of the maceration that is inevitable in this location. Note the sharp demarcation of the lesions. Treatment of psoriasis in the diaper area can be difficult. Low-potency topical corticosteroids should be used judiciously with the use of barrier creams.

Pustular psoriasis Figures 12-28 and 12-29 illustrate pustular psoriasis. Both are examples of the disease in relatively mild form, but even in these the suppurative quality of the lesions can be appreciated. Severe pustular psoriasis, also known as the von Zumbusch form, is a rare and potentially life-threatening disease.

Pustular psoriasis may be triggered by physical or emotional stress, a number of medications, or the abrupt discontinuation of steroid therapy, and must be differentiated from other disorders, including pustular drug eruptions.

Pustular psoriasis Patients with this form of disease can develop shaking chills, fever, and leukocytosis. Numerous superficial pustules develop on psoriatic plaques and on uninvolved skin. Over a brief period of time, the pustules enlarge and become confluent; lakes of pus form. The process may eventuate in an exfoliative erythroderma. Hospitalization and careful supportive therapy are important aspects of treatment.

Pustules with identical appearance may be seen in a deficiency of interleukin 1 receptor antagonist (DIRA), and this disorder may also cause lytic lesions in the bones. Treatment for this disorder is anakinra, a recombinant form of the human interleukin-1 receptor antagonist.

Pityriasis rubra pilaris This is a chronic and often severe cutaneous disorder that may sometimes begin during childhood. Depending on the stage and location of the disease process, the appearance varies. The most unique distinguishing manifestation of this disease is the red-orange perifollicular keratotic papules that are usually located on the dorsal surfaces of the fingers and hands. The “nutmeg grater” appearance in these areas is pathognomonic of pityriasis rubra pilaris.