Severe Psoriasis Presenting in 3-Year-Old Child With Nail Dystrophy

The patient’s psoriasis reoccurred at age 11, 6 months off ixekizumab, and gradually worsened (See Figure 2.) During that time ixekizumab received FDA-approval for pediatric use but the patient’s insurance denied access to this treatment, with stepedits that required a failed trial of methotrexate. Weekly oral methotrexate was started 1 month later at 15 mg (0.3 mg/kg). His skin worsened over the next 2 months, and he complained of lower back and finger pain, prompting methotrexate increase to 20 mg (0.4 mg/kg) per week for 2 more months without significant benefit. Monthly laboratory monitoring was unremarkable. Ixekizumab was again prescribed and denied, based on additional insurance criteria requiring a trial of adalimumab (Humira^®, Abbvie), despite lack of FDA-approval for this indication in children. The patient’s psoriasis improved to 5% BSA after 5 months of bimonthly adalimumab injections. A third attempt at access to ixekizumab was denied by his insurance.

Psoriasis is a chronic, inflammatory skin condition that affects more than 7 million Americans. Although this condition most often presents in young adults (peak onset 15-35 years old), 30% of cases begin in childhood, sometimes misdiagnosed as “nummular” eczema, or tinea.^1,2,3 Plaque psoriasis is the most common phenotype in both children and adults,⁴ with acuteonset small “guttate” plaques classically developing after an infection such as strep throat, tonsillitis, or a respiratory infection.³ Other variants include nail, scalp, inverse, palmoplantar, and pustular psoriasis. In infants, psoriasis classically involves the face, diaper area, and scalp (often referred to as “cradle cap”).^3,4 Geographic tongue is an associated, but underrecognized, often incidental finding.⁵ In children, nail and scalp involvement are often assumed to be fungal infections.^6,7 Skin lesions triggered by physical trauma, a phenomenon known as “koebnerization,” is a characteristic feature of psoriasis.^3,4 Grooming-associated koebnerization is believed to contribute to the increased incidence of scalp involvement in girls.⁴ Nail involvement may be subtle, manifesting as fine pits that can support the diagnosis, and has been associated with a higher risk of psoriatic arthritis.⁶ However, in severe cases, subungual hyperkeratosis, onycholysis, discoloration, and paronychia can be disfiguring and painful, and interfere with function. The Child-CAPTURE registry identified nail involvement in psoriasis as a predictor of more severe disease.^7,8

The pathogenesis of psoriasis involves immune dysregulation that has historically responded to treatment with broad systemic immunosuppressant medications (eg, cyclosporine and methotrexate). In the past 20 years, targeted biologic blockade of inflammatory cytokines has yielded increasingly better efficacy with fewer adverse effects. Biologic agents developed for the treatment of psoriasis include those that target TNFα, IL12/23, IL23, and IL17.⁹ These agents were initially studied and FDA-approved for treating psoriasis in adults. Additional pediatric trials and access to the evolving pipeline of medications was restricted for a minimum of 7 years after initial approval for each product. As of 2021, 4 biologic agents have been approved for pediatric use (Table 1.)^9,11,12,13

Indications for systemic treatment include >10% BSA and sites that are difficult to treat topically (nails, groin, scalp) as well as failure to respond to standard-of-care topical therapy. Lowdose methotrexate used off-label is still considered a first-line systemic option and may be more well-tolerated in children than in adults. However, long-term treatment with methotrexate requires monitoring with baseline and frequent follow-up blood tests. Emerging level 1 data support safe and effective use of selected biologic agents in children without routine labs.⁹ Pediatric psoriasis can be a therapeutic challenge. Several parameters must be considered when electing the optimal treatment for a specific patient. These include primary morphology, speed of progression, age, gender, associated morbidities, medication cost, and access. In the absence of FDAapproved pediatric labelling, age has been the most common reason for insurance coverage denial for using biologic medications in children with psoriasis, which is an illegal form of age discrimination.¹⁴ Pediatric labelling has improved access for some treatments, but remains a challenge.

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