While sometimes individuals can develop GPP without any history of previous psoriatic disease, “In most cases, they've had a history of psoriasis, they were given a systemic steroid, and now the psoriasis has come back with a vengeance and has turned into a pustular form,” Dr. Hsu says. For this reason, Dr. Hsu tells providers to avoid prescribing systemic steroids to patients with psoriasis.
Other factors that may trigger pustular psoriasis include smoking, infections or injuries, stress, pregnancy, and the use of tumor necrosis factor and interleukin-17 inhibitors, such as those used for the treatment of other inflammatory conditions, like rheumatoid arthritis, Crohn’s disease, and plaque psoriasis. 
Along with its distinct presentation, pustular psoriasis types also appear pathogenically distinct from plaque-type psoriasis, Dr. Hsu says. While the exact cause of pustular psoriasis remains unclear, Dr. Hsu and colleagues describe the possible involvement of the interleukin-36 pathway in a recent review published in Dermatology and Therapy. 
Because pustular psoriasis has such a significant impact on patients, effective treatment is critical; however, it is a challenging condition to manage since many of the treatments for plaque psoriasis are not as effective for pustular psoriasis, Dr. Hsu says.
For patients with extensive disease, treatments are available. In Dr. Hsu’s practice, she initiates treatment with cyclosporine or acitretin, noting that they both have drawbacks. She prescribes daily treatment with acitretin and a topical corticosteroid unless the individual is a female of childbearing age. In this case, she prescribes treatment with cyclosporine.
Acitretin is an oral retinoid and should only be prescribed to male patients, or females who are not of childbearing age, as it can have a negative effects on the fetus. “If it is taken with any type of alcohol, it will convert to etretinate, which stays in the body fat for up to three years. … [and may cause] birth defects,” Dr. Hsu says.
Cyclosporine is a calcineurin inhibitor and is used as an immunosuppressant medication. It has the potential to cause renal failure and hypertension, and the FDA recommends cyclosporine not be used longer than one year.  “So, this is not a long-term solution. You have to think about what you are going to do next,” Dr. Hsu says.
At the one-month mark, if the patient is clear on the daily dose of acitretin, Dr. Hsu says she begins to wean the patient by lengthening the dose interval to every other day and then every third day. If the patient continues to stay clear, she advises maintaining on a topical corticosteroid. If, at any point, the patient flares, Dr. Hsu goes back to the last dose at which the patient was able to maintain clearance.
Similarly, in individuals who are female and of childbearing age, and to whom she prescribes cyclosporine, she assesses clearance at one-month. If the patient is clear, she will begin to wean the patient. If the pustular psoriasis flares during that process, she will transition the patient to a biologic. The problem is that the efficacy of biologics for pustular psoriasis has been inconsistent, she says.
“When we use biologics for plaque-type psoriasis, they work. But, for pustular psoriasis, it can be hit or miss,” Dr. Hsu says. “There is not one biologic that works better than another for pustular psoriasis.” She pointed to studies that demonstrate guselkumab may be effective,  but says the evidence for many of the biologics has been inconsistent.
In addition to treatment, Dr. Hsu also advises patients with any type of psoriasis to see their primary care provider due to the association with metabolic syndrome. This is a cluster of conditions that include high blood pressure, high blood sugar, abnormal cholesterol and triglyceride levels, as well as excess abdominal fat, and which may increase an individual’s risk for heart disease, stroke, and type 2 diabetes. 
While research into how pustular psoriasis develops has improved understanding of the disease and may lead to new, more effective therapies in the future, Dr. Hsu says there remains a strong need for an effective, long-term treatment option.