Erythrodermas, Immunodeficiency, and Metabolic Disorders

Atopic dermatitis

Severe generalized atopic dermatitis is unusual in neonates, though may often be seen in infancy. Because atopic dermatitis is such a common problem, it is the most common cause of acquired erythroderma in infants (see Chapter 15 ). Classic infantile atopic dermatitis involves the scalp, cheeks, and extensor surfaces of the extremities and may not appear until the infant is several months of age. When the distribution is generalized and the onset is early, diagnosis can be more difficult.

The presence of pruritus, an almost invariable feature of this condition, is not always apparent in neonates and young infants. There is often a family history of atopy. Typically, the diaper region is spared, even in cases of widespread atopic dermatitis, as a result of the moist, occlusive environment of diapered skin. In contrast to infants with severe metabolic or immunologic disease, infants with atopic dermatitis usually grow normally and thrive, assuming the disease is recognized and treated promptly. Severe and long-standing disease, however, can be a cause of failure to thrive. Other clinical features such as repeated pneumonia, viral infections such as HSV or molluscum, and skeletal abnormalities may suggest the autosomal dominant hyper-IgE syndrome (HIES) or the autosomal recessive DOCK8 deficiency syndrome. Atopic dermatitis generally responds rapidly to appropriate therapy with topical anti-inflammatory agents and emollients. Skin biopsy in atopic dermatitis demonstrates acanthosis (thickening of the epidermis) and varying degrees of spongiosis (epidermal edema), as well as lymphohistiocytic inflammatory infiltrates, often with scattered eosinophils and plasma cells.

Seborrheic dermatitis

Seborrheic dermatitis is a common problem during the neonatal period and is generally easily recognized (see also Chapter 15 ). Typically, there is scaling and erythema involving seborrheic areas such as the scalp and body folds. The yellow, greasy, scalp scale may encompass the entire forehead, including the eyebrows, and erythema and maceration can involve body folds such as the retroauricular areas, neck, axillae, and groin. Occasionally, a more diffuse pattern of seborrheic dermatitis can occur, which must be distinguished from atopic dermatitis, neonatal candidiasis, psoriasis, and other causes of infantile erythroderma ( Box 18.1 and Fig. 18.1 ).

The distribution of the dermatitis is more helpful than any other criterion in differentiating between atopic and seborrheic dermatitis, but it can be difficult and sometimes impossible to differentiate the two conditions accurately early in their course. Although the scalp can be red and scaly in both conditions, seborrheic dermatitis tends to involve the groin and other body folds, which are generally spared in atopic dermatitis. As treatment for both conditions in infancy is similar, from a practical standpoint accurate differentiation can be an academic exercise. However, the course of this disease differs: seborrheic dermatitis usually resolves over several months, whereas atopic dermatitis often persists for several years. Skin biopsy findings in seborrheic dermatitis are similar to those in atopic dermatitis. There is mild acanthosis, spongiosis, and a mild lymphohistiocytic inflammatory infiltrate; parakeratotic scale may be present.

If clinical features suggest widespread seborrheic dermatitis in an infant who is otherwise well and thriving, and the skin readily clears after the application of low- to mid-potency topical corticosteroids without chronic rebound when therapy is tapered, the diagnosis of seborrheic dermatitis is probably accurate. Otherwise, alternative diagnoses should be considered. Severe seborrheic dermatitis in a child who is not thriving can suggest an immunodeficiency or Netherton syndrome.

Psoriasis

Less than 1% of all cases of psoriasis are said to occur in children less than 1 year of age. Infantile psoriasis can be difficult to diagnose because of its clinical similarity to both seborrheic dermatitis and atopic dermatitis. Infantile psoriasis can look like that seen in older individuals, with discrete oval erythematous plaques with white scale involving the trunk, extremities, and face. Psoriatic plaques in infants may have less hyperkeratosis than usually seen in adults. Facial involvement is more common in the infant, and the scalp, palms, and soles may have diffuse erythema and scaling. A periumbilical distribution may be helpful in distinguishing psoriasis from either seborrheic or atopic dermatitis. In contrast to atopic dermatitis, psoriasis in young infants often involves the diaper area because it develops in areas of injured skin (the Koebner phenomenon), e.g. after a prior irritant or Candida diaper dermatitis (see Chapter 16 ). Pustular psoriasis, either in a diffuse distribution or limited to the palms and soles, may be seen rarely. A positive family history for psoriasis is helpful. Some neonatal or infantile cases are HLA-B17 positive.

Rarely, infantile psoriasis is generalized, a presentation that has been reported in young infants, and can even be present at birth. Erythroderma can evolve into and even alternate with pustulosis. Infantile generalized pustular psoriasis can be associated with lytic bone lesions, and be complicated by the acute respiratory distress syndrome (pulmonary capillary leak syndrome) that is also described in adults with acute generalized pustular psoriasis (B. Krafchik pers. comm.). Skin biopsy can be helpful in differentiating causes of neonatal erythroderma and in some cases, is diagnostic. Biopsy usually shows psoriasiform hyperplasia with elongated rete ridges and parakeratotic scale, often containing neutrophils. Occasionally, the diagnostic finding of a spongiform micropustule or microabscess in the upper epidermis is seen. Skin biopsies of erythrodermic psoriasis are often indistinguishable from those of any chronic dermatitis, lacking the classic features, and it may take several biopsies and close observation over time to confirm the diagnosis.

Localized psoriasis may be treated with emollients and low-potency topical corticosteroids, but often clears only partially or recurs. Cases of infantile psoriasis may prove to be mild and occasionally even clear completely as the child gets older. The prognosis of generalized erythrodermic or pustular psoriasis in infancy is more guarded, and treatment usually requires systemic retinoid therapy, as well as supportive care.

Pityriasis rubra pilaris

Diffuse scale and erythema with palmoplantar keratoderma can suggest pityriasis rubra pilaris (PRP). Juvenile cases and even erythrodermic newborn presentations have been described. Systemic therapy has been successful when indicated clinically.

Drug exanthem

Erythroderma due to medications is fortunately rare, though cases in pediatric patients, including infants and neonates have been described. Severe reactions such as Stevens–Johnson syndrome or the drug reaction with eosinophilia and systemic symptoms (DRESS) represent particular challenges for clinicians. The approach to patients, regardless of age, requires a high index of suspicion and a broad understanding of other causes of erythroderma.

Acute generalized exanthematous pustulosis

Acute generalized exanthematous pustulosis (AGEP) presents acutely with pustules overlying diffuse erythema after exposure to an offending medication, mercury exposure or viral illness. Antibiotics reported to cause AGEP in infants include amoxicillin and amoxicillin-clavulanic acid. AGEP has also been reported in infants with no antibiotic exposure, suggesting an infectious trigger in these cases. Subcorneal pustules are seen by skin biopsy (see Chapter 20 ).

Boric acid poisoning

Boric acid poisoning is now very rare, but was seen in the past as a result of the frequent use of boric acid-containing powders and lotions for the treatment of diaper dermatitis. It presents with a maculopapular eruption that can evolve into a generalized erythroderma, the appearance of which has been likened to a boiled lobster. A report of this in an adult after ingestion of a boric acid-containing pesticide, has been published. A positive Nikolsky sign and desquamation are additional features. Like staphylococcal scalded skin syndrome, the condition may be accentuated in periorificial and intertriginous areas. Alopecia may also develop. Affected infants are usually ill, with fever, irritability, vomiting, and diarrhea, which can progress to shock and even death.