The Skill Checkup series provides a quick, case-style interactive quiz, highlighting key guideline- and evidence-based information to inform clinical practice.
A 49-year-old nonsmoking woman in the United States has an 8-year history of mild inverse psoriasis that mostly affects her groin, and sometimes underarms and under her breasts. The lesions are smooth and light red. She is an avid runner, which creates a lot of friction on her skin. For 7 years and 10 months, she had been keeping the symptoms of inverse psoriasis at bay by avoiding wearing synthetic fibers; removing wet, sweaty clothing as soon as possible; and keeping the intertriginous areas clean and dry with the help of powder. However, these areas have recently become darker red, harder to keep dry, and have increased in size, covering 2% of her body surface area (BSA).
As a result, she was given triamcinolone 0.1% to apply to the affected areas twice a day for 8 weeks. At her next visit, 8 weeks after starting treatment, the redness had receded somewhat to its original lighter red, but the amount of surface area affected had not changed. In addition, she also now has slightly raised reddish scales on both knees with hints of a whitish, silvery hue in places. They are not tender on palpation. Together with the previously existing inverse psoriasis, the total BSA affected by lesions is now 4%. These new unsightly lesions are hard for her to hide while wearing shorts to run and bike during the summer months in Georgia, and she doesn't want people to stare or think she is contagious. Both the patient's father and her sister have a history of psoriasis.
Based on the case presentation, the patient appears to have plaque psoriasis on her knees in addition to her established inverse psoriasis.
Inverse psoriasis, also known as flexural or intertriginous psoriasis, is a variety of plaque psoriasis that involves the body folds, such as the underarms, groin, and under the breasts. The lesions typically appear moist, smooth, and shiny. This condition is frequently accompanied by classical plaque psoriasis in other body areas.
The lesions on the patient's knees are consistent with plaque psoriasis, which can lead to silvery white scales that typically appear on the knees, elbows, scalp, and/or trunk.
Pustular psoriasis is characterized by yellowish pustules on an erythematous base. Often, these lesions will be tender when palpated. This does not apply to the patient's case.
Psoriatic arthritis is a complication that occurs in approximately 30% of patients with psoriasis. If left untreated, psoriatic arthritis could lead to significant morbidity, irreversible joint damage, and poor patient-reported outcomes; therefore, early identification and treatment are very important.
There is a known association between inflammatory bowel disease, including Crohn's disease and ulcerative colitis, and psoriasis. However, at 0.7% for Crohn's disease and 0.5% for ulcerative colitis, their prevalence in patients with psoriasis is much lower than that of comorbid psoriatic arthritis and psoriasis, according to data from a global systematic review and meta-analysis.
While rheumatoid arthritis and psoriasis share some overlapping features, they do not frequently coexist. Likewise, systemic lupus erythematosus is an autoimmune condition that can lead to cutaneous manifestations, but its co-occurrence with psoriasis is not common.
So far, none of the various manifestations of psoriatic arthritis has been observed in this patient, so it is determined that the patient does not have comorbid psoriatic arthritis.
A BSA of 4% reflects moderate psoriasis, per joint guidelines from the American Academy of Dermatology (AAD) and the National Psoriasis Foundation (NPF), which indicate the following BSA cutoffs for disease severity:
- Mild: < 3%
- Moderate: 4%-10%
- Severe: > 10%
However, BSA is only one factor to be weighed when determining disease severity. The same guidelines state that psoriasis can be deemed severe with a BSA involvement < 10% if the disease causes serious emotional distress or intractable pruritus, or if it affects special areas such as the hands, feet, scalp, face, or genitals.
Now that the plaque psoriasis has developed, the patient's total psoriatic involvement has increased to moderate in severity.
A topical phosphodiesterase type 4 (PDE4) inhibitor would be the most appropriate monotherapy for this patient's multi-type psoriasis. PDE4 inhibitors work inside the cell to break down cyclic adenosine monophosphate and help modulate that inflammatory environment. In a phase 2b, double-blind clinical trial, 73% of patients treated with a topical PDE4 inhibitor showed improvements in intertriginous areas within 6 weeks.
According to joint AAD-NPF guidelines, most people with mild to moderate psoriasis will be able to control the disease using topical medications or phototherapy.
While topical corticosteroids are a common treatment option for mild to moderate psoriasis, the generally thin, delicate skin of the areas affected by inverse psoriasis make it more prone to local side effects. Along with the face, intertriginous areas are at increased risk of developing adverse effects owing to corticosteroid treatment. Therefore, even though the patient would be able to use a corticosteroid for the plaque psoriasis on her knees, it would not be the most appropriate option for the inverse psoriasis she has in other areas.
Few studies suggest that topical vitamin D analogues might be effective for inverse psoriasis, and many of the studies that do exist provide low-quality evidence.
Currently, the evidence on the use of IL-12/23 inhibition for the treatment of inverse psoriasis is too limited for the AAD-NPF to recommend it, although they do recommend its use for moderate to severe plaque psoriasis.
After a detailed discussion with the patient about lifestyle, personal preferences, and the characteristics of each treatment option, including their risk/benefit profiles, the patient was initiated on a topical PDE4 inhibitor.
The patient's treatment response should be evaluated in 3 months. In 2017, the medical board of the NPF published defined patient-centered treatment targets based on the consensus of 25 psoriasis experts. The group agreed that patient response to a new therapy should be evaluated 3 months post-initiation. The target response is to reach a BSA of ≤ 1% in 3 months, whereas the response would be deemed acceptable if BSA is ≤ 3% or ≥ 75% improved at 3 months from baseline. During the maintenance period, the group decided that the target response should be ≤ 1% BSA every 6 months.
The patient is asked to schedule a 3-month follow-up visit after initiating her PDE4 inhibitor therapy to evaluate the new treatment's response.
Editor's Note: Skill Checkups are wholly fictional or fictionalized clinical scenarios intended to provide evidence-based educational takeaways.
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