Transient neonatal pustular melanosis presents as pustules, ruptured pustules with a collarette of scale (that represents the remnants of the pustule roofs), and small hyperpigmented macules (in the sites of previous pustules). It occurs in 4% to 5% of African American infants and in fewer than 1% of Caucasian infants. The face, chin, neck, and shoulders are the areas most commonly affected. If vesiculopustules are present, they disappear within 1 to 2 days. In contrast, the pigmented macules may take weeks or even months to fade. The pustules are 1 to 3 mm in diameter, usually are flaccid, and have no surrounding erythema (see color Fig. 68.10 in color section). Most have very little content on rupturing, including perhaps a few neutrophils. The cause of this disorder is unknown, but it appears
to be an entirely benign condition. A Gram stain of the contents of a pustular lesion should prove most helpful in differentiating transient neonatal pustular melanosis from bacterial pustulosis. No therapy is necessary.

A condition that may mimic neonatal acne is neonatal cephalic pustulosis caused by infection with the yeasts Malassezia furfur or M. sympodialis. At 2 to 3 weeks of age, inflammatory papules and pustules appear. Unlike neonatal acne, however, neonatal cephalic pustulosis is not characterized by comedones and lesions are distributed more widely, involving the scalp and trunk, as well as the face. To confirm the diagnosis, a potassium hydroxide preparation performed on a scraping of a lesion will reveal yeast spores. Neonatal cephalic pustulosis resolves without treatment but a topical antiyeast preparation may be applied to hasten its disappearance.

Congenital cutaneous candidiasis is an uncommon disorder that is acquired in utero. Lesions are present at birth or develop shortly thereafter. The newborn’s skin often is diffusely erythematous and scaly. Tiny papules, vesicles, and pustules also are present. Examination of a scraping of the lesions should reveal the budding hyphae and pseudohyphae of Candida. Congenital candidiasis typically is limited to the skin, although premature infants may develop systemic involvement with pneumonia or sepsis. Cutaneous lesions are treated with a topical antiyeast preparation (e.g., nystatin).

Vesicular lesions, whether grouped (as is typical) or scattered (as sometimes occurs in the neonatal period), always should suggest the possibility of herpes simplex virus (HSV) infection. The majority of infants in whom herpes infections develop are born to mothers who are unaware of their own infection with the virus. Infection usually is acquired during passage through the infected birth canal, although ascending infection, particularly in association with premature rupture of the amniotic membranes, also is recognized. Neonatal HSV infection usually has its onset during the second or third week of life, but it may appear at birth or as late as 4 weeks of age.

Three forms of infection are recognized, each accounting for approximately one-third of all cases. Skin, eye, and mouth (SEM) infection begins at a mean of 11 days of age. Classically, infants present with clustered vesicles on an erythematous base. Lesions are concentrated on the head, particularly in areas of trauma, such as the site of placement of a scalp electrode (Fig. 129.5). Over several days, the vesicles become pustules, rupture, and form crusts. Occasionally, lesions will be widespread or in a distribution mimicking that of herpes zoster. Involvement of the mucous membranes produces shallow ulcers. If untreated, as many as 70% of infants with SEM infection develop disseminated disease.

Disseminated HSV infection has its onset at a mean of 11 days of age producing symptoms and signs suggestive of bacterial sepsis. Multiple organ systems are involved, including the liver, lungs, brain, and adrenal glands. Approximately 60% of affected infants also have skin lesions. The mortality rate associated with disseminated disease is high, even with effective treatment. Central nervous system infection begins at a mean of 17 days of age and is heralded by fever, altered sensorium, seizures, and coma. Sixty percent of affected infants have associated skin lesions.

The importance of immediate diagnosis of HSV infection cannot be overemphasized. Suspicious lesions should be tested by viral culture or polymerase chain reaction. In experienced hands, rapid diagnosis may be obtained via the performance of a Tzanck preparation. Parenteral acyclovir therapy should be administered without delay.

Neonatal varicella is an uncommon condition resulting from in utero infection in the 2 to 3 weeks before delivery. The lesions in neonates are similar to those seen in older infants and children, with crops of macules and papules developing into teardrop-like vesicles. The diagnosis is suspected by a maternal history. A Tzanck preparation will reveal multinucleated giant cells, but this finding does not differentiate between varicella and herpes simplex virus infection. Because disease may be severe, it is recommended that newborns whose mothers develop varicella 5 days before to 2 days after delivery receive varicella-zoster immune globulin.

Incontinentia pigmenti (IP) is a rare genodermatosis with cutaneous abnormalities that occur in four stages. The earliest lesions are vesicles on erythematous bases that are arranged in a linear pattern on the trunk or extremities (Fig. 129.6; color Fig. 68.11 in color section). The lesions are present at birth or appear within the first 2 weeks of life. Individual lesions last 1 to 2 weeks but new lesions may appear for months. In this stage, IP often is confused with herpes simplex virus infection or impetigo. The second stage, which may overlap with the first, is characterized by verrucous (wart-like) papules located primarily on the extremities, but not necessarily at the sites previously affected by vesicles. This stage peaks at 12 to 26 weeks of age and resolves within 1 to 2 years. The third stage is one of tan to slate-gray hyperpigmentation that is arranged in a linear or whorled pattern on the trunk and extremities. This stage
also resolves gradually. The final stage, which may or may not occur, is composed of subtle, hypopigmented, atrophic patches of skin, especially on the legs.

IP is an X-linked dominant disorder caused by mutations in the NEMO gene. More than 97% of cases occur in females, suggesting that the condition is lethal for males in utero. It is a multisystem disorder affecting tissues derived from the neural crest. The majority of patients have extracutaneous disease involving the central nervous system (e.g., seizures, spastic paresis, microcephaly, or mental retardation), eye (e.g., strabismus, blindness, cataracts, or optic nerve atrophy), teeth (e.g., cone-shaped or irregularly shaped teeth), hair (e.g., alopecia), and bones (e.g., hemivertebrae, extra ribs, or syndactyly). Thus, children with IP require a multidisciplinary approach to management.

Eosinophilic pustular folliculitis is an uncommon disorder that usually occurs in neonates. However, a more widespread and persistent form has been described in children with human immunodeficiency virus infection. The disease is characterized by recurrent crops of pruritic, follicular, papulopustular lesions. The lesions tend to coalesce into plaques and occur most commonly on the scalp, face, chest, and back. Smears from the pustules show eosinophils, and peripheral eosinophilia is common. The lesions are sterile. The cause of the lesions is not known and the course varies. Treatment with topical corticosteroids of moderate potency has met with modest success.

Infants commonly suck their hands or fingers in utero. Occasionally, a thick-walled bulla on the dorsum of the hand, fingers, or forearm will result (Fig. 129.7). Their characteristic appearance and location and the observation of the infant sucking the affected area are helpful clues to this diagnosis. Treatment is supportive; a topical antibiotic and dressing may be applied as needed.

Bullous impetigo is caused by infection with strains of Staphylococcus aureus that elaborate toxins (exfoliative toxins A and B) that damage intercellular adherence resulting in the formation of bullae. It may occur at a few days of age, but generally it begins during the second or third week. Individual lesions are bullae that have a small rim of erythema. The bullae rupture easily, leaving an eroded, moist base that forms a crust and is surrounded by a rim of scale, the remnant of the blister roof. To confirm the diagnosis, the contents of a bulla may be cultured and a Gram stain performed.

Infants who appear well and have limited disease may be treated with an oral antistaphylococcal antibiotic. If signs of systemic infection are present, however, the infant should be evaluated appropriately and treated parenterally.

Elaboration of exfoliative toxins also may lead to staphylococcal scalded skin syndrome, characterized by generalized erythema and the appearance of bullae, particularly in areas of trauma. There may be widespread loss of skin resulting in fluid loss and thermal instability. (See Bullae in the section Skin Lesions in Infancy, Childhood, and Adolescence, later.)

Epidermolysis bullosa (EB) represents a group of rare hereditary diseases. The disorders result from defects in proteins involved in anchoring the epidermis to underlying structures. This, in turn, causes skin fragility with vesicles, bullae, and erosions. Depending on the disease type, involvement of the mucosae of the mouth or gastrointestinal or respiratory tracts may be present. Some forms of EB present at or shortly following birth with blisters and erosions resulting from delivery or handling (see color Fig. 68.16 in color section). The diagnosis of EB is based on family history, clinical findings, and cutaneous biopsy. Treatment is supportive, including gentle handling and bathing; the use of a soft nipple for feeding and loose-fitting diapers and clothing; and the application of a topical antibiotic to erosions. EB is discussed more completely later in this chapter (see Bullae in the section Skin Lesions in Infancy, Childhood, and Adolescence, later).

Bullae and vesicles are an unusual presentation of congenital syphilis (Fig. 129.8). Most common on the extremities, they rupture rapidly, leaving an eroded surface. More commonly, flat-topped papules and plaques are seen that affect the mucocutaneous junctions, including the angles of the mouth and perineum (e.g., condyloma lata). Ovoid, slightly scaly, salmon-colored macules may also be present on the trunk and extremities (Fig. 129.9).

Purpuric lesions of infants infected with rubella virus in utero are caused most commonly by thrombocytopenia. On occasion, the purpuric lesions take on an infiltrative or nodular quality, producing a blueberry-muffin appearance (Fig. 129.10). The lesions actually are areas of extramedullary hematopoiesis rather than true cutaneous hemorrhage.

Petechiae in conjunction with intrauterine growth restriction, hepatosplenomegaly, and hyperbilirubinemia always should raise the question of congenital infection. Cytomegalovirus is the most prevalent of these infections. Most of the purpuric lesions are the result of thrombocytopenia. Blueberry muffin–like lesions also have been documented.

Subcutaneous fat necrosis is a disorder of unknown cause that often occurs in association with birth trauma. Lesions typically are not present at birth but appear within the first weeks of age. The areas most commonly affected are the cheeks, buttocks, back, arms, and thighs. Lesions are irregular, hard, erythematous, or violaceous nodules that seem nontender. The size of the nodules varies. Occasionally, the lesions may become calcified, but generally they resolve spontaneously in 1 to 2 months without scarring. Some infants may develop symptomatic hypercalcemia that must be treated appropriately. No therapy of the skin lesions is necessary.

The nevus sebaceus (of Jadassohn) is present at birth and usually is found on the scalp (color Fig. 68.3 in color section). The area is devoid of hair, slightly raised, smooth or with a velvety texture, and yellow to yellow-orange. Lesions vary in size and can be found on the face as well (Fig. 129.11). Sebaceous nevi represent benign hamartomas containing an increased number of sebaceous glands. Most represent isolated cutaneous
abnormalities but large or extensive lesions may be associated with mental retardation, seizures, or ophthalmic or skeletal malformations. Due to a small risk of malignant transformation (e.g., to a basal cell carcinoma) after puberty, elective excision may be considered at adolescence.

Epidermal nevi usually are present at birth but may appear during childhood or adolescence. They are verrucous-appearing, skin-colored or somewhat hyperpigmented papules or plaques that measure 2 to 10 cm in size (Fig. 129.12). Over time, lesions become darker, thicker, and rougher and may develop an unpleasant odor. Large or extensive linear lesions may indicate the presence of a neurocutaneous disorder with central nervous system (e.g., mental retardation, seizures), eye (e.g., strabismus), or skeletal (e.g., hemihypertrophy, kyphoscoliosis) abnormalities, and may be a feature of the Proteus and CHILD syndromes. The cause of epidermal nevi is not known but they represent hamartomas (benign tumors composed of normal but disorganized skin components). There is no risk of malignant transformation. If treatment is desired, application of a keratolytic agent, surgical excision, or laser therapy may be considered.

Sclerema neonatorum is an uncommon, rapidly spreading thickening of the subcutaneous tissue that occurs in preterm or ill infants during the first few weeks of life. The skin becomes tight, shiny, and nonpitting. Affected infants usually are seriously ill with other problems and rarely survive once this condition appears.

The small, rubbery, smooth subcutaneous nodules characteristic of dermoid cysts occur most frequently on the head and neck. Congenital lesions formed from embryonic ectoderm, they are lined by stratified squamous epithelium. Almost 40% are periorbital, and approximately 30% occur in the eyebrows. The lesions usually are solitary and asymptomatic, and they are managed by surgical excision. Lesions in the midline of the scalp or forehead or at the glabella may have an intracranial extension. Therefore, imaging of the bone and central nervous system should be conducted prior to excision.

Aplasia cutis congenita is characterized by a congenital absence of the skin. Affected infants usually exhibit a single lesion that may be a round or oval ulcer or atrophic scar that is located on the scalp at or near the vertex (Fig. 129.13). Individual lesions range in size from 1 to 3 cm. Occasionally, there is an associated defect in the cranium. Although aplasia cutis congenita most often represents an isolated cutaneous abnormality, it may be associated with limb abnormalities, sebaceous or epidermal nevi, epidermolysis bullosa, or other malformations. Treatment rarely is required as ulcers heal spontaneously. For infants with large lesions, skin grafting may be required.

Salmon patches are the most common vascular lesions in infancy, seen in almost one-half of all newborns. These dull-pink macules composed of dilated dermal capillaries are most prevalent over the glabella, eyelids, and nape of the neck. Facial lesions tend to fade with time, generally within the first years of life. Neck lesions, however, may persist. The macules often are called stork bites (when located at the nape) or angels’ kisses (when located on the face). During crying, older infants and children may demonstrate flushing in areas of previous lesions that have faded.

The benign salmon patch must be differentiated from the port wine stain, which is a congenital, permanent vascular malformation composed of mature vessels. Port wine stains (PWSs) are reddish or reddish purple and typically are darker than salmon patches (Fig. 129.14). They may occur anywhere on the body, although they are seen most commonly on the face. Infants with PWSs involving the distribution of the first and second branches of the trigeminal nerve (upper and lower eyelids, respectively), all three branches of the trigeminal nerve, or both sides of the face are at risk for Sturge-Weber syndrome. In this sporadic disorder, the vascular malformation involves not only the skin, but also the ipsilateral leptomeningeal vessels, particularly those in the parietooccipital region. Slow flow through these vessels causes hypoxic injury that, in turn, may result in seizures or contralateral hemiparesis. The vascular malformation also may affect the ipsilateral eye. Abnormalities of the choroid and episcleral vessels may lead to retinal detachment or glaucoma, respectively. PWSs on the extremities usually represent an isolated abnormality and only rarely are associated with overgrowth of the extremity (Klippel-Trenaunay syndrome). Because PWSs tend to become darker and thicker with time and may develop surface bleeding, children with significant facial PWSs should be referred for consideration of pulsed dye laser therapy early in life.

Harlequin color change is a curious phenomenon usually noted in the first few days of life in low-birth-weight infants. When such infants are placed on their sides, a sharp midline demarcation develops in the color of their bodies, with the upper one-half turning pale and the lower one-half turning deep red. A change in position results in resolution of the color change. The phenomenon can last for a few weeks and is attributed to a temporary imbalance in the regulatory mechanisms of the autonomic nervous system.

Hemangiomas are benign vascular tumors that proliferate during the first 6 to 9 months of age and then begin to involute, resulting in complete regression in most children. Hemangiomas may be present at birth but typically appear at 2 to 4 weeks of age. They are observed in as many as 10% of 1-year-olds. In some newborns, a hypopigmented macule, within which are telangiectatic vessels (a prehemangioma), heralds the appearance of a hemangioma. Superficial hemangiomas (often called strawberry hemangiomas) occur in the upper dermis. Deep hemangiomas appear as nodules with normal overlying skin and a bluish discoloration. Lesions with superficial and deep components are termed mixed hemangiomas (color Fig. 68.4 in color section).

Hemangiomas grow rapidly during the first 6 months of life, reach a quiescent stage when the patient is 6 to 12 months old, and then begin to regress when the child is between 12 and 18 months old. Signs of regression include patches of gray on the surface of the lesion (Fig. 129.15). By the time the patient is 5 years old, 50% of lesions will have regressed; by age 9, 90% will have done so. After regression, an area of atrophy, telangiectases, or hypopigmentation may remain. With large lesions, redundant skin may be the major cosmetic defect. Deep hemangiomas may not show complete regression.

Complications of hemangiomas are infrequent. Erosions are the most common complication, particularly for lesions in the diaper area (Fig. 129.16, color Fig. 68.4 in color section).
Hemangiomas that become eroded are painful, may become infected, and are prone to scar. They should be treated with a barrier cream and, if infected, an oral antibiotic. If they fail to heal within 1 to 2 weeks, consultation with a pediatric dermatologist is indicated. Bleeding occurs rarely and usually responds well to the application of direct pressure. Infants with multiple cutaneous hemangiomas (color Fig. 68.5 in color section) occasionally have associated visceral lesions in the central nervous system, lungs, liver, or intestines. If present, visceral lesions may result in high-output cardiac failure or hemorrhage. Most infants with systemic involvement present by 2 months of age with respiratory distress, hepatomegaly, a heart murmur, or anemia. The presence of multiple cutaneous hemangiomas should prompt the conduct of a careful history and physical examination. If suspicion exists about visceral involvement, initial screening studies might include a complete blood count, chest radiograph, abdominal ultrasonography, and stool for occult blood. Other potential complications of hemangiomas are presented in Table 129.1.

Since most hemangiomas are small and do not threaten vital structures, no therapy is needed. Complicated hemangiomas should be managed in conjunction with a pediatric dermatologist and other specialists as appropriate. Depending on the lesion type and location, therapeutic options include oral prednisone (often at doses of 2 to 4 mg/kg/day) or intralesional corticosteroids. Ulcerated hemangiomas may be treated with pulsed dye laser. Life-threatening lesions (e.g., those associated with Kasabach-Merritt syndrome) may require interferon alfa or other agents.

Pityriasis rosea typically produces oval thin plaques composed of tiny papules with a fine scale. At times, particularly in more deeply pigmented patients, papules may be prominent (Fig. 129.22). The cause of pityriasis rosea is unknown but is believed by many to be viral. The disorder occurs most commonly in teenagers and young adults but has been described in infants. Recurrent episodes are uncommon, and small epidemics have been reported among individuals in close contact.

In about one-half of patients, pityriasis rosea begins with the appearance of a herald patch, a solitary erythematous patch, or a minimally elevated plaque. At times, this lesion may be mistaken for tinea corporis. One to two weeks later, the typical generalized eruption begins. The ovoid lesions of pityriasis rosea are concentrated on the trunk and have their long axes parallel to lines of skin stress. Thus, their distribution on the patient’s back gives the appearance of the boughs of a fir tree. Often viewing the rash from across the room facilitates seeing this characteristic pattern. Individual lesions are minimally elevated and erythematous or hyperpigmented. Most lesions are covered by a fine, wrinkled scale (Fig. 129.23). At times, particularly
in more deeply pigmented individuals, lesions may be more papular in appearance or the eruption may involve the extremities and face, sparing the trunk (i.e., inverse pityriasis rosea). Occasionally, the lesions may be urticarial wheals or bullae, or may become purpuric.

The lengthy course of this disorder should be emphasized to the patient or the parents. The eruption itself develops over a 2-week period, persists for 2 weeks, and then fades over another 2 weeks. This pattern varies greatly, however, and rashes lasting 3 to 4 months are not unusual. Pruritus occurs in up to one-half of patients and may be managed with an emollient containing menthol and phenol, a topical nonsensitizing anesthetic (e.g., pramoxine), or an oral antihistamine. Judicious exposure to sunlight (avoiding burning) may hasten the resolution of the eruption. One report suggested that erythromycin was effective but its results have not been confirmed.

The differential diagnosis of pityriasis rosea includes dry nummular eczema and psoriasis. Secondary syphilis may produce an eruption similar to pityriasis rosea, although patients usually are ill, have lymphadenopathy, and exhibit lesions on the palms and soles. Nevertheless, a serologic test for syphilis should be considered if the patient is sexually active.

Psoriasis is an inherited disorder whose onset occurs before 16 years of age in 25% to 45% of patients. Usually, the lesions are distinctive, with well-demarcated, erythematous papules or plaques covered with a silvery scale (see color Fig. 68.18 in color section). The scale tends to build up in layers, and its removal may cause a bleeding point (Auspitz sign). The papules enlarge to form plaques. Usually, the distribution is symmetric, with plaques commonly appearing over the knees and elbows because they are sites of repeated trauma. Other common sites of involvement are the eyebrows, ears, umbilicus, and gluteal cleft. Frequently, the scalp shows a thick, adherent scale; often, the nails demonstrate punctate stippling or pitting or become discolored and thickened, and the palms and soles may show scaling and fissuring. The Koebner phenomenon (i.e., the appearance of rash at sites of physical, thermal, or mechanical trauma) often is evident.

A variety of inciting factors in addition to trauma have been associated with the appearance of psoriatic lesions. An interesting factor in children is the development of guttate psoriasis, a condition characterized by multiple, small, teardrop-like lesions associated with pharyngeal or perianal Streptococcus pyogenes infection (Fig. 129.24). Other factors implicated are sunburn, drug eruptions, and viral infections. The histologic picture is one of hyperproliferation of the epidermis.

The course of psoriasis is unpredictable. Initial treatment consists of the application of an emollient. Most patients, however, will require therapy with a regimen consisting of an appropriate topical corticosteroid and calcipotriene; topical tar preparations also may be employed. Exposure to sunlight, with care taken not to burn the skin, often is beneficial. Patients with severe, recalcitrant disease may require treatment with an oral psoralen combined with ultraviolet light or methotrexate.

The differential diagnosis in childhood includes such uncommon disorders as pityriasis rubra pilaris, parapsoriasis, and lichen planus. Occasionally, atopic dermatitis may be confused with psoriasis, but psoriasis typically is not pruritic. Pityriasis rosea, tinea corporis, and seborrheic dermatitis also may mimic psoriasis.

Scaly, erythematous papules are characteristic of juvenile dermatomyositis. The lesions, called Gottron papules, classically are found over the knuckles, elbows, and knees. A violaceous discoloration of the upper and lower lids (i.e., heliotrope) and malar area and nailfold telangiectases frequently are present.

Juvenile dermatomyositis may be limited to the skin (i.e., amyopathic dermatomyositis, dermatomyositis sine myositis) or be associated with symmetrical muscle pain and proximal muscle weakness. Evaluation of patients suspected of having juvenile dermatomyositis should include measurement of muscle enzymes, including creatine kinase, aldolase, aspartate aminotransferase, and lactic dehydrogenase. Occasionally, muscle biopsy, electromyography, or magnetic resonance imaging is required. Systemic corticosteroids are the mainstay of therapy, although topical corticosteroids or hydroxychloroquine may be used to control skin disease.

A wide variety of rashes have been associated with systemic lupus erythematosus (SLE). The so-called butterfly rash, a slightly raised, erythematous or violaceous thin plaque or patch with fine scale located over the malar areas and bridge of the nose, is most often associated with SLE. Patients may also exhibit discoid lesions, round, well-demarcated, erythematous to violaceous plaques with fine telangiectases, an adherent scale, and areas of atrophy. The lesions appear most commonly on the face and scalp and in the ears. Other cutaneous lesions include transient erythematous annular lesions in sun-exposed areas (subacute cutaneous lupus erythematosus), red or purple nodules, scaling patches on the dorsa of the fingers, and scarring and nonscarring alopecia.

The papules in lichen planus, a disorder found mostly in adults, characteristically are polygonal. When the lesions are examined closely, the flat-topped papules seem to form rectangles, squares, and other shapes (Fig. 129.25). The classic lesions are violaceous and occur most frequently on the wrists and
extensor surfaces of the forearms. They may coalesce to form plaques. Significant scaling of the lesions may occur on the lower extremities. Oral lesions, consisting of tiny white papules in lacy patterns, may occur on the buccal mucosa. Nail dystrophy, including roughening of the nail surface or longitudinal ridging, is not common in children with lichen planus.

Lichen planus is intensely pruritic. Excoriations can lead to secondary infection and to the occurrence of lesions at sites of trauma. The cause of the eruption is unknown, and the lesions persist for 8 to 18 months. Therapy consists of the application of a moderate- to super-potent corticosteroid and the administration of an antihistamine to control pruritus. In severe or unresponsive cases, oral corticosteroids or retinoids may be indicated.

Pityriasis rubra pilaris is an uncommon disorder of unknown cause characterized by erythematous, scaly papules that may coalesce to form plaques. The papules are centered about follicles and have tapered tips. A characteristic feature is the presence of islands of normal tissue between the joined plaques. Patients also develop thick, adherent scale on the scalp (similar to that seen in psoriasis) and thickening of the palms and soles, which may be marked. The degree of skin involvement varies widely. Pruritus is absent or minimal. Most cases of pityriasis rubra pilaris occur sporadically but familial clustering has been observed.

The course of pityriasis rubra pilaris usually is prolonged, interspersed by remissions and exacerbations. For patients with mild forms of the disease, topical agents, including emollients, keratolytics, tretinoin, or corticosteroids, may be beneficial. Oral retinoids and other systemic therapies are required for those with severe disease.

Pityriasis lichenoides is an uncommon disorder with two variants: an acute form (known as pityriasis lichenoides et varioliformis acuta [PLEVA]) and a chronic type (known as pityriasis lichenoides chronica). Both produce a generalized erythematous papular and macular eruption, usually over the trunk and extremities. The lesions persist for months or recur in periodic eruptions. The acute form produces lesions that may be hemorrhagic, vesicular, pustular, or even necrotic. Initially, the eruption may be mistaken for varicella. The chronic form is characterized by reddish brown papules that have an adherent scale and range from a few millimeters to 1 cm in diameter. The wafer-like plaques may be confused with pityriasis rosea. The cause of pityriasis lichenoides is unknown. Some cases resolve with exposure to ultraviolet light; others improve with prolonged erythromycin therapy.

Lichen striatus, a self-limited eruption most common in children, is characterized by the rapid development of multiple small papules arranged in a linear, band-like pattern over an extremity (Fig. 129.26). The bands may be 1 to several centimeters in width, irregular or fairly uniform, and continuous or interrupted; they occur most commonly on the lower extremities. The papules may be scaly and generally are skin-colored or erythematous, although in deeply pigmented individuals they may be hypopigmented. The cause of this distinctive lesion is unknown. It has a duration of a few weeks to as long as 3 years. As resolution begins, papules disappear, leaving hypopigmentation that may persist for several months. Topical corticosteroids and keratolytics may hasten its resolution. Linear epidermal nevi, linear psoriasis, and linear lichen planus are included in the differential diagnosis.