Given the characteristic clinical presentation, the most likely diagnosis is psoriasis.
Dr. Lawrence Eichenfield
Psoriasis is a chronic immune-mediated disease that is characterized by well-demarcated thick scaly plaques on face, scalp, and intertriginous skin. Psoriasis is more common in adults than children, but the incidence of psoriasis in children has increased over time.1 Clinical presentation of psoriasis includes erythematous hyperkeratotic plaques, usually sharply demarcated. Pediatric patients may have multiple small papules and plaques less than 1 cm in size – “drop-size” – known as guttate lesions. Scalp and facial involvement are common in children. Chronic, inflamed plaques with coarse scale can involve ears, elbows, knees, and umbilicus, and nail changes can include pits, ridges, hyperkeratosis, and onycholysis or “oil spots.” While the diagnosis is clinical, biopsy can sometimes be useful to distinguish psoriasis from other papulosquamous conditions. Psoriasis in children is associated with obesity, higher rates of cardiovascular disease over a lifetime, as well as arthritis and mental health disorders.2
What’s the differential diagnosis?
The differential diagnosis for psoriasis can include papulosquamous diseases such as nummular eczema, pityriasis rosea, and pityriasis rubra pilaris. Tinea corporis may also be considered.
Dr. Al Reem Al-Nabti
Nummular eczema, also known as “discoid eczema” is characterized by multiple pruritic, coin-shaped, eczematous lesions that may be actively oozing. The term “nummular” is derived from the Latin for “coin,” as lesions are distinct and annular. It is commonly associated with atopic dermatitis, and may be seen with contact dermatitis as well. Oozing, lichenification, hyperpigmentation and limited extent of skin coverage can help distinguish nummular dermatitis from psoriasis.
Pityriasis rosea is a common self-limited disease that is characterized by the appearance of acute, oval, papulosquamous patches on the trunk and proximal areas of the extremities. It usually begins with a characteristic “herald” patch, a single round or oval, sharply demarcated, pink lesion on the chest, neck, or back. Pityriasis rosea and guttate psoriasis may show similar clinical findings but the latter lacks a herald patch and is often preceded by streptococcal throat infection.
Dr. Mira Choi
Pityriasis rubra pilaris is a rarer inflammatory disease characterized by follicular, hyperkeratotic papules, thick orange waxy palms (palmoplantar keratoderma), and erythroderma. It can also cause hair loss, nail changes, and itching. The rash shows areas with no involvement, “islands of sparing,” which is a signature characteristic of pityriasis rubra pilaris. Skin biopsies are an important diagnostic tool for pityriasis rubra pilaris. In the case of circumscribed pityriasis rubra pilaris, it may look similar to psoriasis, but it can be differentiated in that it is often accompanied by characteristic follicular papules and involvement of the palms, which are more waxy and orange in color.
Dr. Lawrence F. Eichenfield
When evaluating annular scaly patches, it is always important to consider tinea corporis. Tinea corporis will commonly have an annular border of scale with relative clearing in the center of lesions. In addition, when topical corticosteroids are used for prolonged periods, skin fungal infections can develop into “tinea incognito,” with paradoxical worsening since the immune response is suppressed and the fungal infection worsens.
Our patient had been previously treated with topical corticosteroids (medium to high strength) and topical calcineurin inhibitors without significant improvement. Other topical therapies for psoriasis include vitamin analogues, tazarotene, and newer therapies such as topical roflumilast (a phosphodiesterase-4 inhibitor approved for psoriasis in children over 12 years of age).3,4 In addition, as the indications for biological agents have been expanded, there are various options for treating psoriasis in children and adolescents when more active treatment is needed. Systemic therapies for more severe disease include traditional systemic immunosuppressives (for example, methotrexate, cyclosporine) and biologic agents. The four biologic agents currently approved for children are etanercept, ustekinumab, ixekizumab, and secukinumab. Our patient was treated with ustekinumab, which is an injectable biologic agent that blocks interleukin-12/23, with good response to date.
Dr. Al-Nabti is a clinical fellow in the division of pediatric and adolescent dermatology; Dr. Choi is a visiting research physician in the division of pediatric and adolescent dermatology; and Dr. Eichenfield is vice-chair of the department of dermatology and professor of dermatology and pediatrics, all at the University of California, San Diego, and Rady Children’s Hospital, San Diego. They have no relevant disclosures.
References
1. Tollefson MM et al. J Am Acad Dermatol. 2010;62(6):979-87.
2. Menter A et al. J Am Acad Dermatol. 2020;82(1):161-201.
3. Mark G et al. JAMA. 2022;328(11):1073-84.
4. Eichenfield LF et al. Pediatr Dermatol. 2018;35(2):170-81.