An 18-month-old girl presented for evaluation of chronic diaper dermatitis. The mother reported an intermittent eruption since age 1 month, with skin peeling and bleeding during flares. Multiple topical therapies, including zinc oxide paste, nystatin and hydrocortisone acetate 2.5% ointment, had been used with minimal improvement. Review of systems was normal. She had no known drug allergies. The father reported a patch of dry, scaly skin on his right lower leg with no other family history of skin or autoimmune disorders.
Physical examination revealed a well-developed, well-nourished, active, alert infant. Examination of the diaper area revealed welldemarcated, erythematous plaques with minimal white scale (Figure).
The flexural creases were spared. The remainder of the cutaneous examination, including hair and nails, was normal.
Figure. Photograph of the diaper area showing well-demarcated erythematous plaques.
Psoriasis presenting in the diaper area
Psoriasis affects 2% of the population in the United States, with nearly one-third presenting in childhood.1'2 Psoriasis is a chronic inflammatory skin condition characterized by welldefined round or oval plaques with a thick white or silvery scale. Adults often present with the typical pattern of large plaques with thick silvery scale on the elbows, knees, and scalp.
Children may present with this appearance to their lesions, but often, childhood psoriasis presents with plaques that are smaller, with finer scale. In addition, children can present with a guttäte (drop-like) form, with the sudden onset of multiple discrete papules on the trunk, limbs, and face, often following a streptococcal infection, or an inverse form with flexural involvement (eg, retroauricular, axillae, groin folds, gluteal cleft, umbilicus), with minimal to no surface scale.3'4'5 Nail involvement in children is less common, but they can present with nail pitting, onycholysis, or distal hyperkeratosis.5
Infants may present with a chronic diaper dermatitis that does not respond to standard therapy.5 Psoriasis involving the diaper area can be difficult to distinguish from irritant, candidai, or seborrheic diaper dermatitis. In psoriasis, the affected area is erythematous with sharply demarcated margins, and the inguinal folds may or may not be involved. This is in contrast to irritant diaper dermatitis, which shows a less well-demarcated rash sparing the inguinal folds, and seborrheic dermatitis, which often involves the folds or creases. When accompanied by perioral or aerai dermatitis, the differential diagnosis also includes acrodermatitis enteropathica (zinc deficiency). This described patient experienced a flare of pustular psoriasis, a rare subtype, shortly after presentation.
Histologically, psoriasis is characterized by hyperproliferation and abnormal differentiation of keratinocytes with an inflammatory cell infiltratioa Although the cause is unknown, genetics and environmental factors play a role. An association has been found between psoriasis, particularly early-onset, and certain Human leukocyte antigen alíeles of the major histocompatibility complex located on chromosome 6p.6 In addition, susceptibility loci have been identified on chromosomes Iq, 3q, 4q, and 17q, although the specific genes have not yet been identified.7'11
Treatment is aimed at decreasing epidermal proliferation and inflammation. Low-potency topical corticosteroids (eg, 2.5% hydrocortisone acetate or 0.05% aclometasone dipropionate ointment) are used on areas with thin skin, such as the face and genitalia. Moderate- to high-potency topical corticosteroids can be used for trunk and extremity involvement. In addition, off-label use of the calcineurin inhibitors, pimecrolimus cream and tacrolimus ointment, have proven effective for facial and intertriginous areas. Other topical therapies include calcitriol (1,25-hydroxyvitamin D3), coal tar preparations, and tazarotene (topical retinoid).12"15 Rarely, for more severe widespread disease, systemic agents are used.
Most children with psoriasis can be well controlled with topical therapy alone. However, a chronic relapsing course with the need for intermittent treatment is a feature of most cases.
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