Chapter 357. Neonatal Dermatology

The skin of a newborn infant differs from adult skin in several ways that place infants at increased risk for thermal instability, skin damage, percutaneous infection, and percutaneous toxicity from topically applied agents. The neonatal body surface area-to-weight ratio is up to 5 times greater than that of an adult, and the thickness of infant skin is 40% to 60% less.1 Attenuated rete ridges, formed from comparatively fewer stem cells at the basal layer, provide a relatively limited area of surface attachment to an immature dermis, resulting in relative skin fragility. Sebaceous glands are hypertrophic for several weeks after birth, under the influence of fetal and maternal androgens, but eccrine function does not mature until after term, placing newborns at risk for hyperthermia with overbundling. The vernix caseosa is composed of sloughed keratinocyte and sebaceous gland lipids, with a higher proportion of glandular lipids in boys.

The most clinically significant difference between the skin of a premature and that of a term infant is the barrier function of the most superficial layer of the epidermis, the stratum corneum. Infants born before 32 weeks of gestation have a very thin stratum corneum. Although even in premature neonates, the stratum corneum matures within 2 weeks after birth, premature infants suffer from significant transepidermal water loss with associated hypothermia and fluid and electrolyte disturbances. These problems are proportional to the degree of prematurity. Transepidermal water loss is 10 times higher for an infant born at 24 weeks of gestation than for a term neonate.2 Barrier function rapidly improves during the first 2 weeks after birth, but infants born at 25 weeks or less can have increased transepidermal water loss for significantly longer than 4 weeks after gestation.3 Benign clinical interventions such as barrier creams or ointments can dramatically decrease these losses. During this period, cutaneous contact with chemicals that can cause neurotoxicity, such as hexachlorophene, or alter thyroid function, such as povidone iodine, should be avoided.2,4 Desiccated skin is even more susceptible to injury, providing a portal of entry for invading microbes and increasing the risk of disseminated infection.

Aplasia Cutis Congenita

The congenital absence of skin is a cutaneous anomaly most often seen at the scalp vertex. Sharply marginated lesions may present either singly or as multiple ulcers, bullae, or scars that measure up to several centimeters in diameter (eFig. 357.1). Aplasia cutis can have underlying skull defects, and larger irregular defects may extend to the dura or meninges. These larger lesions are more often familial and may be complicated by meningitis, hemorrhage (which can be fatal), or sagittal sinus thrombosis.5 Aplasia cutis of the trunk and extremities is often strikingly symmetric in distribution. Histologically, aplasia cutis is characterized by absent epidermis, diminished dermis and adnexal structures, or, in full-thickness lesions, the absence of all skin layers.

Several distinct subtypes of aplasia cutis have been described on the basis of distribution, mode of inheritance, and associated abnormalities. Most aplasia cutis congenita occurs sporadically, but autosomal dominant and autosomal recessive transmission have also been well documented. Associated abnormalities include cleft lip and palate, limb anomalies, cutaneous organoid nevi, and epidermolysis bullosa. Aplasia cutis may mark underlying cranial defects, spinal dysraphism, omphalocele, or gastroschisis. In addition, scalp defects have been associated with specific teratogens (methimazole, intrauterine varicella, and herpes simplex) and malformation syndromes (trisomy 13, Johanson-Blizzard syndrome, Adams-Oliver syndrome, amniotic band disruption complex, and the ectodermal dysplasias). Extensive aplasia cutis has been associated with elevated α-fetoprotein in maternal serum and amniotic fluid.

The cause of aplasia cutis congenita is unknown, but incomplete closure of the neural tube or embryonic fusion lines has been proposed as a possible etiology.6 The findings of a twin fetus papyraceous and/or a placental infarct have suggested vascular thrombosis as a cause in infants with lesions on the trunk and limbs.

Cutaneous and bony lesions usually heal spontaneously over a period of weeks to months. A hypertrophic or atrophic patch of alopecia remains. Lesions that fail to heal or produce cosmetically unacceptable scars can be excised with primary closure after appropriate imaging is done to rule out underlying defects.

Midline Lesions

Midline circumscribed or annular hypertrichosis, dimples, sinuses, skin tags, nodules, and cysts may be isolated skin findings or may mark underlying developmental defects. The differential diagnosis of lesions on the brow or nose includes dermoid cyst or sinus, glioma, and encephalocele. Congenital defects that present as a midline scalp nodule include encephalocele, meningocele, aplasia cutis, dermoid cyst or sinus, and heterotopic brain tissue. If the diagnosis of a midline scalp lesion is clinically uncertain, skin biopsy should be postponed until after radiographic imaging by computed tomography or magnetic resonance imaging. These studies may miss small associated intracranial connections, however.

A midline pit or nodule on the neck may represent a cervical cleft or thyroglossal duct cyst or sinus. A remnant of respiratory epithelium known as a bronchogenic sinus or cyst presents at birth as a nodule or pit at the suprasternal notch. Branchial cleft anomalies, cysts or sinuses, are located along the preauricular area, pinna, and lateral neck. Aberrant branchial arch development is associated with several multiorgan syndromes, including Townes-Brocks, Treacher Collins, Goldenhar, Hallermann-Streiff, Pierre Robin syndromes, and branchiootorenal dysplasia. These sinuses and cysts can be watched expectantly or electively removed by surgical excision to prevent drainage or infection.

A variety of midline lumbosacral skin lesions, including pits, lipomas (often manifesting as a deviated gluteal cleft), skin tags or pseudotails, localized hypertrichosis, hemangiomas, and nevus flammeus, may mark occult spinal dysraphism (eFig. 357.2). Sacral dimples or sinuses are common lesions and are of more concern when they occur superior to the gluteal cleft or in combination with other cutaneous signs of dysraphism. Diffuse hypertrichosis and nevus flammeus are also commonly seen over the lumbar spine, and in isolation, they are less likely to be a sign of spinal dysraphism. In contrast, radiographic imaging is indicated for sacral hemangiomas, lipomas, or skin tags.

Amniotic Bands

Amniotic bands cause circumferential ringlike constrictions on the skin, most commonly on the extremities. They are present at the time of birth and appear to be caused by separation of the amnion from the chorion, giving rise to strands of amnion, which disrupt normal morphogenesis. Amniotic bands can cause a multitude of other abnormalities, including limb amputations, syndactyly, thoracoabdominal wall defects (eg, gastroschisis, omphalocele), and craniofacial clefts.

Supernumerary Nipples

Supernumerary nipples are reddish brown papules or dells that occur anywhere along the embryologic milk lines of the chest, abdomen, or, rarely, the inguinal area (eFig. 357.3). They may be accompanied by breast tissue and are sometimes mistaken for melanocytic nevi. Further evaluation and treatment is usually unnecessary. Supernumerary nipples may be electively removed by surgical excision.

Accessory Tragus

Accessory tragi are pedunculated flesh-colored papules occurring anywhere from the preauricular area to the angle of the mouth (eFig. 357.4). They are present at birth and can be multiple or bilateral. They are usually localized lesions but can be associated with other branchial arch syndromes. Association with deafness and renal abnormalities is controversial, and screening is only recommended if there are other worrisome features present. They should be removed by an experienced surgeon because most lesions contain cartilage and may have connection with the external ear canal.

Supernumerary Digits

Most common on the fifth finger, supernumerary digits can range from subtle papules to full-sized digits. These lesions often contain cartilage and nerves; thus, they should not be ligated but instead removed by a surgeon with nerve dissection to avoid development of a traumatic neuroma.

Median Raphe Cysts

These white-colored papules along the ventral penis, scrotum, and perineum represent incomplete closure of the urethral and/or genital folds (eFig. 357.5). They are usually asymptomatic and resolve over time without treatment.

Nevus Sebaceus

Usually a localized lesion on the scalp or face, nevus sebaceus presents at birth as a hairless linear plaque of coalesced salmon- to yellow-colored papules (Fig. 357-1). A biopsy reveals absent to malformed hair follicles with an abundance of sebaceous glands. Because of the 10% to 30% risk of tumor formation, especially basal cell carcinoma, removal by adolescence is usually recommended.7

Epidermal Nevus

Epidermal nevi are composed of verrucous-appearing, tan to brown, linear coalescing papules, which can be present at birth but often develop later in childhood. The distribution and size is variable, but lesions are more commonly localized, and the neck, trunk, and extremities are common sites. Treatment is difficult because recurrence is common after destruction or excision.

Sebaceous Hyperplasia

Numerous tiny, pale yellow papules representing hypertrophic sebaceous glands are seen on the nose, forehead, cheeks, and upper lip of full-term newborns. The condition resolves with waning maternal androgen levels during the first weeks of life.

Milia

Milia are tiny cysts walled by incompletely canalized follicular or ductal epithelium and filled with sloughed keratinocyte and sebaceous debris. Milia are most common on the face of full-term newborns but may be seen on other areas. Epstein pearls, yellow papules often found on the hard palate, are intraoral milia. Milia usually disappear within a few weeks.

Neonatal Acne

The small inflammatory papules and pustules of neonatal acne may be present at birth or develop within the first 2 to 3 weeks of life. Comedones are characteristically absent. The etiology is unclear, but current hypotheses suggest an association with Pityrosporum species versus the traditional theory of maternal and fetal androgen influence. Therefore, neonatal acne may not be a true form of acne, and “neonatal cephalic pustulosis” has been proposed as a replacement term. The condition is rarely severe enough to require treatment and usually resolves spontaneously within 2 to 3 months. Pustules caused by Pityrosporum (Malassezia furfur) contain characteristic spores and short hyphae; these resolve promptly with application of topical antifungal creams. Infantile acne typically develops at 2 to 3 months of age (or can be persistent neonatal acne) with inflammatory papules, pustules, and comedones. Persistent or severe acne in an infant is a sign of adrenal or androgen excess in the minority of cases. Normal growth velocity and bone age are usually sufficient to rule out extracutaneous disease in an otherwise healthy infant. Nodulocystic acne warrants dermatologic referral for more aggressive therapy.

Nevus Simplex

Colloquially known as a salmon patch, angel kiss (on the eyelids), or stork bite (on the posterior hairline), these pink-to-red blanching macules are found on the majority of newborns. They may be distributed anywhere along the midline from the brow to the nape of the neck as well as on the eyelids and alar creases. Facial lesions nearly always fade with time, but nuchal patches often persist. Nevus simplex may represent dilated superficial vessels as a result of vasomotor immaturity. These transient lesions should be distinguished from nevus flammeus (port-wine stain), a persistent vascular anomaly that can occur on any skin site but is commonly located on the face. Involvement of the eyelid in the V-1 or V-2 distribution necessitates serial eye examination to rule out associated glaucoma. Sturge-Weber syndrome is extremely uncommon but is commonly associated with bilateral facial nevus flammeus or unilateral lesions involving all 3 branches of the trigeminal nerve. Large lesions on the extremities may be associated with underlying venous varicosities and ipsilateral hypertrophy (Klippel-Trenaunay syndrome) or isolated hypertrophy (less commonly hypotrophy) of the limb.

Cutaneous Vasomotor Instability

Cutaneous vasomotor instability is common in newborns and may present as cutis marmorata, acrocyanosis, or harlequin color change. Cutis marmorata is a reticulate and mottled appearance of the skin caused by an uneven distribution of superficial capillary blood flow. The pattern is often precipitated by exposure to cold and is more common in preterm than in term infants. Persistent or recurrent cutis marmorata beyond the neonatal period is called livedo reticularis. Livedo reticularis is often physiologic but can be associated with a variety of congenital and acquired pathologic conditions, including Down syndrome, trisomy 18, and Cornelia de Lange syndrome, as well as vasculopathy or frank vasculitis attributable to a wide range of infectious, inflammatory, or neoplastic processes. Cutis marmorata telangiectatica congenita is a congenital anomaly that approximates the reticular pattern of cutis marmorata but is fixed in a focal, often unilateral distribution (eFig. 357.6). The condition may be complicated by associated skin atrophy and ulceration, ipsilateral soft tissue, or even bony hypotrophy. Acrocyanosis results from the pooling of venous blood in the hands and feet; the deep purple color does not mark a pathologic process in an otherwise healthy infant and is reversed by warming. Harlequin color change is transient erythema or duskiness of the dependent half of the body, a sharp midline demarcation, and pallor of the upper half that resolves with change in position.

Mongolian Spots

Mongolian spots are more common in infants with dark skin types and occur in 80% to 90% of Asian and African American newborns. They are discussed in detail in Chapter 361.

Many conditions cause blisters and pustules in the newborn. Vesicles are defined as small intraepidermal or subepidermal pockets of clear fluid. If the lesions are large (> 1 cm), they are referred to as bullae. Pustules are filled with purulent fluid. Diseases in this category range from the totally innocuous and self-limited to the severe and life threatening. Often, initial empiric broad-spectrum systemic antimicrobial therapy is warranted, especially in unstable premature infants. A family history of blistering diseases and physical examination, including examination of the placenta, can focus the differential diagnosis. Bullae and widespread involvement should prompt a more aggressive workup. The differential diagnosis of infectious and noninfectious causes of blisters, pustules, and erosions in the newborn are summarized in Table 357-1. Infectious causes are discussed in Section 17 and genetic causes are discussed in detail in Chapter 360. The relatively more common noninfectious causes of vesicles and pustules in the neonate are discussed in more detail here.

Sucking Blisters

Sucking blisters are common, transient lesions that result from intrauterine sucking. Typically, 1 or 2 blisters or erosions are present at birth on the radial forearm, wrist, or dorsal thumb or index finger. The diagnosis is usually confirmed by observing the infant sucking vigorously on the affected area.

Miliaria

Also called prickly heat, this common skin finding results from incomplete canalization of the eccrine ostia with resultant accumulation of sweat droplets within the skin. Three clinical variants reflect the depth of obstruction. Miliaria crystallina are superficial, subcorneal vesicles (eFig. 357.7). Miliaria rubra occur within the epidermis, accompanied by focal rupture of the duct and an inflammatory response, producing erythematous papules and pustules. Miliaria profunda, uncommon in neonates, are deeper edematous papules occurring within the dermis. Miliaria is precipitated by excessive heat or bundling. Common sites include the forehead, torso, and arms. The condition is self-limited and relieved by placing the infant in a thermoneutral environment.

Erythema Toxicum Neonatorum and Transient Neonatal Pustular Melanosis

Common, transient, and innocuous eruptions, erythema toxicum neonatorum and neonatal pustular melanosis may occur simultaneously and may share a common pathophysiology. The exact etiology is unknown, but a recent theory suggests erythema toxicum may be related to an inflammatory reaction to microbes penetrating into the skin through the hair follicle.8Erythema toxicum occurs in 50% to 70% of term newborns, equally in boys and girls, but is uncommon in premature infants.9 In most infants, the onset is in the first 2 days with resolution within 1 week. Three types of skin lesions may be present in varying proportions: erythematous macules, wheals, and vesiculopustules, usually arising from an erythematous base (eFig. 357.8). Lesions can occur almost anywhere on the body, but palmoplantar and perioral sparing are diagnostic features. Transient neonatal pustular melanosis occurs in 5% of term African American infants and in less than 1% of Caucasian infants.10 The eruption is always present at birth or within the first 24 hours. Lesions evolve from noninflammatory pustules that rupture, leaving transient collarettes of scale surrounding hyperpigmented macules that may persist for several weeks (Fig. 357-2). The pustular phase is evanescent and may occur in utero, leaving only pigmented macules at birth. The eruption may occur on any part of the skin but usually involves the face, neck folds, hands, and feet. The differential diagnosis of pustular eruptions is extensive and includes infectious processes that require immediate treatment (see Table 357-1). Microscopic examination of the vesicle roof prepared with potassium hydroxide is clear of yeast, whereas Wright-stained smears of the base are without the multinucleated giant epithelial cells that characterize herpesvirus infections. Pustular contents show no bacteria on Gram stain and, in the case of erythema toxicum, usually contain eosinophils, whereas those of transient neonatal pustular melanosis contain neutrophils. Skin biopsy is indicated if the diagnosis is uncertain.

Acropustulosis of Infancy

This intensely pruritic eruption consists of vesicles and pustules localized mainly to the palms, soles, and lower extremities (eFig. 357.9). Lesions may be present at birth but usually develop in early infancy. It is more common in males and in African Americans. Lesions reoccur in crops every 2 to 3 weeks and fade over the next 7 to 10 days. The condition closely mimics scabies, but repeated skin scrapings are negative for evidence of mites, and empiric treatment for scabies is ineffective. Skin biopsy is not usually necessary but will reveal an intraepidermal vesicle containing eosinophils or neutrophils. Treatment with potent topical steroids or oral antihistamines may relieve symptoms. The use of ultrapotent (class I) topical steroids may be justified in severe cases.

Eosinophilic Pustular Folliculitis

A variant of eosinophilic folliculitis occurs in infants and, rarely, neonates. It is characterized by pruritic, recurrent crops of pustules. Unlike acropustulosis of infancy, the lesions are most commonly seen on the scalp, although they can occur on the trunk and extremities as well. Skin biopsy reveals a perifollicular infiltrate of eosinophils. The etiology is unknown, but potent topical steroids and oral antihistamines seem to be helpful. The lesions eventually resolve over several months.

Incontinentia Pigmenti

Incontinentia pigmenti is an uncommon X-linked dominant blistering genodermatosis that occurs predominantly in females (see Chapter 360). It is caused by mutations in the nuclear factor-kappa B (NF-κB) essential modulator (NEMO) gene, which encodes a protein that regulates various cytokines and is essential in protection against apoptosis.11,12 Incontinentia pigmenti is a multisystem disorder affecting the skin, teeth, hair, nails, eyes, and central nervous system. Skin manifestations occur in 4 variable, overlapping stages: vesicular, verrucous, hyperpigmented, and hypopigmented atrophic lesions.13 Vesicular lesions are often present at or shortly after birth, usually lasting from 2 weeks to 4 months. The distribution of the vesicles is distinctively linear, following the lines of Blaschko, and can be focal or extensive (eFigs. 357.10 and 357.11). Biopsy or smear of the vesicles reveals numerous eosinophils and can be helpful in confirming the diagnosis. Cultures should also be performed to rule out infectious causes. Later, the development of subsequent stages of the disease confirm the diagnosis. The verrucous lesions occur more commonly on the extremities with onset around 2 to 6 weeks of age (eFig. 357.11). Hyperpigmented linear streaks often occur in areas previously not affected by vesicles and develop at 3 to 6 months of age with resolution by puberty or adulthood. The hypopigmented lesions develop in adolescents and adults as subtle, atrophic hypopigmented linear lesions most commonly seen on the legs. Alopecia and nail dystrophy are also seen in association with incontinentia pigmenti. Common noncutaneous associations include eye and teeth abnormalities; thus, patients should be followed by an ophthalmologist and have early dental intervention. Central nervous system involvement has been reported to be as high as 30%; unfortunately, preventative intervention is unlikely to be helpful.

Vesicles and pustules can provide a valuable clue to the diagnosis of congenital bacterial, viral, and mycotic infections. Other signs that warrant prompt evaluation include bullae and extensive erosions, erythroderma, petechiae, and purpura. The cardinal clinical and diagnostic features of infectious and noninfectious causes of blisters, pustules, and erosions in the newborn are shown in Table 357-1. Infectious causes are also discussed in detail in Section 17.

Vesicles and Pustules

Initial diagnostic studies for vesicles include fluid aspirate taken from an intact pustule for Gram stain, Wright stain, fungal, viral, and bacterial cultures and potassium hydroxide preparation (or Calcofluor White immunofluorescence) of the blister roof.The greatest value of rapid bedside testing is confirmation of a life-threatening infection. Congenital candidiasis and congenital herpes simplex are the most common examples. Herpes simplex can be rapidly diagnosed by direct fluorescence examination using antiherpes antibodies. Vesicles on the skin of newborns tend to cluster at sites in contact with the maternal cervix; cutaneous, eye, and/or mouth lesions are presenting signs in one third of infants. Cutaneous candidiasis is confirmed by potassium hydroxide (or Calcofluor White) smear of the blister roof revealing pseudohyphae. In either case, a high index of suspicion must be maintained for the possibility of systemic disease, especially in premature infants. Pityrosporum (Malassezia furfur) folliculitis is confirmed with a potassium hydroxide smear of the blister roof and contents that reveal short hyphae and spores. The diagnosis of bullous impetigo and gram-positive folliculitis is supported by a Wright stain of the blister base revealing polymorphonuclear leukocytes and Gram stain showing gram-positive cocci. In older children with pruritic vesicles on the palms, soles, toe or finger webs, wrists, axillae, or ankles, scrapings from vesicles can be mounted in mineral oil to detect mites, ova, and feces as confirmation of a scabies infestation.

Bullae and Extensive Erosions

These may mark life-threatening diseases that may be impossible to distinguish from one another without skin biopsy. Appropriate therapy depends on correct diagnosis. Skin biopsy of staphylococcal scalded skin syndrome reveals a split in the superficial epidermis. Culture of blister contents is negative because the locus of infection is usually nasopharyngeal, perianal, focus of impetigo, or abscess. A less common condition, toxic epidermal necrolysis, can be distinguished from staphylococcal scalded skin syndrome by histologic evidence of a split at the dermoepidermal junction. A pathognomonic feature of bullous mastocytosis, Darier sign, is a wheal-and-flare response to stroking. Genetic disorders have variable extent of severity and long-term sequelae. Early diagnosis and genetic counseling are important aspects of management. The blisters seen in infants with a form of epidermolysis bullosa are most prominent at sites of friction. Familial forms are classified as simplex, junctional, and dystrophic on the basis of the skin cleavage plane. Electron microscopic analysis and/or immunofluorescence mapping are required for precise diagnosis. Vesicular skin findings that characterize incontinentia pigmenti are distributed in a linear and whorled configuration along the lines of Blaschko (see Chapter 360). This striking pattern is seen with a variety of cutaneous abnormalities resulting from genetic mosaicism.

Erythroderma

Generalized redness and scaling in infancy has an alarming appearance and is often clinically and histologically nonspecific. An infant’s general state of well-being and the family history provide important clues to the underlying cause. Definitive diagnosis may be possible only after a period of observation. The spectrum of disease includes common conditions limited to skin, infections, nutritional deficiencies, and immunologic disorders.

Infectious causes of erythroderma should always be considered first. The differential diagnosis includes systemic candidiasis, staphylococcal scalded skin syndrome, syphilis, and AIDS (see Section 17). Congenital syphilis is uncommon, but its incidence has increased in the last several decades. Also known as “the great mimicker,” syphilis has a wide range of cutaneous signs. The most common cutaneous manifestation of congenital syphilis is symmetric scaling plaques of the arms and legs, especially the medial thighs, palms, and soles, sometimes present at birth and usually within the first few weeks. The more suggestive congenital palmoplantar bullae and erosions occur in only 3% of infected infants. Mucosal lesions are also common and include superficial erosions in the mouth (mucous patches) and moist deep fissures (rhagades) around the eyes, nose, mouth, and anus. The infant’s skin should be carefully examined for more specific primary skin lesions. Laboratory evaluation should include complete blood count; potassium hydroxide preparation (or Calcofluor White immunofluorescence); Tzanck smear; and surveillance cultures of the nasopharynx, rectum, umbilicus, conjunctivae, urine, and blood. Consider syphilis serology and HIV studies in epidemiologically relevant locales.

Erythroderma coupled with failure to thrive, diarrhea, and recurrent infections should prompt a search for metabolic or immunologic abnormalities with assessment of dietary history, electrolytes, protein, albumin, alkaline phosphatase, microscopic examination of hair, and a sweat test. Erythroderma in the neonate may be seen with primary immunodeficiencies (severe combined immunodeficiency, Wiskott-Aldrich, hyperimmunoglobulin E, Omenn syndrome), secondary immunodeficiencies (AIDS, graft-versus-host disease), Langerhans cell histiocytosis, neonatal lupus, and diffuse cutaneous mastocytosis. Erosive, periorificial dermatitis suggests a metabolic or nutritional disorder. Cystic fibrosis is the most common condition in this category. Other possibilities include acrodermatitis enteropathica, biotin-dependent multiple carboxylase deficiency, prolidase deficiency, methylmalonic acidemia, maple syrup urine disease, propionic acidemia, citrullinemia, Gaucher disease, and kwashiorkor. More directed laboratory evaluation includes blood smear for leukocyte vacuoles, HIV screen, plasma zinc, and serum linoleic and arachidonic acids; amino acid and organic acid profiles; biotinidase activity; antinuclear antibody, SS-A, and SS-B titers; quantitative immunoglobulins and tests of cell-mediated immunity; skeletal survey; hair examination; and skin biopsy.

Primary cutaneous conditions should be considered in thriving infants (see Chapter 358). The diagnosis may not be clear until after the neonatal period. Helpful clues to the diagnosis of atopic dermatitis are involvement of the face and extensor extremities with marked sparing of the diaper area. Seborrheic dermatitis and psoriasis frequently involve the diaper area and skin folds. The skin lesions of infantile psoriasis are often sharply circumscribed, but scale may not be prominent. In addition, genodermatoses often present with congenital erythroderma (see Chapter 360). Associated abnormalities and/or skin biopsy help distinguish among the disorders categorized as ichthyoses: lamellar ichthyosis, congenital nonbullous ichthyosiform erythroderma, epidermolytic hyperkeratosis, X-linked ichthyosis, multiple sulfatase deficiency, neutral lipid storage disease, Sjögren-Larsson syndrome, trichothiodystrophy, Netherton syndrome, X-linked dominant chondrodysplasia punctata, and keratitis-ichthyosis-deafness syndrome. The ectodermal dysplasias are a group of disorders with abnormalities of the skin, eccrine glands, hair, teeth, and/or nails. Excessive desquamation resembling postmature skin is a characteristic finding at birth. The best-recognized form is X-linked recessive hypohidrotic ectodermal dysplasia. Infants with this disorder have a decreased ability to sweat, often presenting as recurrent fever of unknown origin.

Petechiae and Purpura

Conditions associated with nonblanching purpuric nodules are listed in Table 357-2. Skin lesions of the classic “blueberry muffin” phenotype represent extramedullary hematopoiesis and occur as a result of congenital infection with syphilis, rubella, cytomegalovirus, coxsackievirus, or toxoplasmosis; severe intrauterine anemia from Rh or ABO incompatibility; or twin transfusion syndrome. Skin biopsy revealing nucleated red blood cells and usually other erythroid and sometimes myeloid precursors distinguish these lesions from the purpuric nodules associated with neoplastic infiltrates from congenital leukemia, neuroblastoma, myofibroma, or vascular tumors (eFig. 357.12). Infectious or inflammatory vasculitis can also present with clinically similar but histologically distinct skin lesions. When the cause of such skin lesions is not obvious, evaluation should include the following: complete blood count with differential, reticulocyte counts, and blood smear examination; liver function tests; cord blood for IgM concentration; maternal and cord blood for congenital infections, including syphilis; viral cultures of the nasopharynx, rectum, and urine; and biopsy of 1 or more skin lesions.