Through research and observation, many of these factors have been identified. The following table, from an article in Cutis, lists a few factors that have been observed as influential in the onset of GPP. Source: "Table II", "Pustular Psoriasis" Farber and Nall, 1993

Genetic factors
Although there are likely to be multiple genetic factors and environmental triggers, mutations causing defects in the IL-36RN, CARD14 and AP1S3 genes have been shown to cause GPP. Diagnosis
Classification
It is important to note that while there are different forms of GPP, they are not exclusive of each other. One can morph into another, or multiple forms can occur simultaneously. von Zumbusch acute generalized pustular psoriasis
Von Zumbusch psoriasis is named after the German dermatologist Leo Ritter von Zumbusch (1874–1940), son of Kaspar von Zumbusch, who described the first documented case of generalized pustular psoriasis in the early 1900s. See Case Report #1. Sometimes all or any of GPP is referred to as von Zumbusch psoriasis, but in the literature it is often distinguished as one specific form of GPP.Eugene M. Farber, MD and colleagues provide a description of von Zumbusch psoriasis in "Pustular Psoriasis", published in Cutis. They describe the pattern as having "waves of widespread or universally fiery redness". The affected areas are "painful and tender". Small sub-corneal pustules form, with sizes originally between 1 and 10 mm in diameter. These pustules may merge to form "yellow-green lakes of pus". The pustules dry out, and "Waves of scarlatiniform [resembling scarlet fever] peeling follow, removing the desiccating pustules".
When GPP does occur in children, it usually appears during the first year of life.Khan et al. reported that in GPP patients ten or younger, less than 12% of cases are preceded by ordinary psoriasis. This differs greatly from GPP cases in adults, where 85% of GPP is preceded by typical psoriatic lesions.According to the article by the University of São Paulo, mentioned above, "The onset of childhood GPP is generally abrupt and accompanied by toxic features." The original acute episode usually lasts a few days, but "repeated waves of inflammation and pustulation may follow." It is important that the disease is managed immediately in order to prevent life-threatening complications, such as infection or [sepsis]. Other complications include "metabolical, hemo-dynamic, and thermoregulatory disturbances" which occur as a result of "alterations of the epidermal barrier. "See Case Report 3

Circinate and annular
This type of psoriasis appears as round lesions. It begins as discrete areas that become raised and swollen. Pustules appear at the edges of the round lesions, creating rings. The pustules then dry out and leave a trail of scale as the lesion grows.See Case Report 4

Treatments
Treatments vary widely, and many different drugs have been documented as being successful. Some medications are successful in some patients, while unsuccessful in others. Below is a list of some medications used to treat GPP:
Etanercept
PUVA
Hydroxyurea
Dapsone
Systemic corticosteroids
Cyclosporin A
Adalimumab
Etretinate
Isotretinoin
Acitretin

Prognosis
GPP is a rare and severe type of psoriasis. It in rare cases it is said to be fatal and in some cases has driven patients to intensive burn units.