# Pustular Psoriasis and Acute Generalized
###### Abstract  
The similarity between pustular psoriasis (PP) and acute generalized exanthematous pustulosis (AGEP) poses problems in the diagnosis and treatment of these two conditions. Significant clinical and histopathologic overlap exists between PP and AGEP. PP is an inflammatory disorder that has numerous clinical subtypes, but all with sterile pustules composed of neutrophils. AGEP is a severe cutaneous adverse reaction that is also characterized by non-follicular sterile pustules. Clinical features that suggest a diagnosis of PP over AGEP include a history of psoriasis and the presence of scaling plaques. Histologically, eosinophil spongiosis, vacuolar interface dermatitis, and dermal eosinophil favor a diagnosis of AGEP over PP. Importantly, PP and AGEP vary in clinical course and treatment. PP treatment involves topical steroids, oral retinoids, and systemic immunosuppressiveants. Newer therapies targeting IL-36, IL-23, IL-1, and PDE-4 have been investigated. The removal of the offending agent is a crucial part of the treatment of AGEP. pustular psoriasis; acute generalized exanthematous pustulosis; severe cutaneous adverse reaction; chronic inflammatory disorder +
Footnote †: journal: medicalica  
0021  
Pustular psoriasis and acute generalized exanthematous pustulosis (AGEP) share similar clinical and histopathologic findings. Historically, AGEP was first described as a variant of PP [1]. A subset of patients within a case series of 104 patients with PP demonstrated an acute pustular eruption that spontaneously resolved without recurrence [1]. These patients lacked a prior history of psoriasis, and the etiology of the eruption was purported to be secondary to medication or infection. Characterization of AGEP as a distinctive entity from PP did not occur until many years later [2]. Importantly, the differentiation of AGEP from PP remains challenging in many instances but is worthwhile due to differences in management and prognosis. A summary of the features of PP and AGEP can be found in Table 1.  
PP is a chronic inflammatory disorder comprised of several distinct subtypes, including generalized pustular psoriasis (GPP), impetigo herpetiformis (IH), palmoplantar pustular psoriasis (PPPP), acrodermatitis continua of Hallopeau (ACH), and annular pustular psoriasis (APP). A uniting factor among each subtype is the presence of sterile, non-infectious pustules characterized by an intraepidermal neutrophil infiltration on histopathology [3]. Further, there is an overlap in genetic factors and treatment responses [3]. PP can exist in conjunction with psoriasis vulgaris (PV), the most prevalent variant of psoriasis, or entirely on its own [4, 5]. The co-occurrence of the two conditions has necessitated the inclusion of PP within the psoriasis spectrum, although this has historically been debated. Of note, PV is most often seen in patients with the PPPP subtype [6]. Theprevalence of PV in patients with PPPP is 10-25 times higher compared to the general population [6]. Psoriasis vulgaris comprises about 80% of cases of psoriasis, while PP makes up the remaining 20% of cases [3]. GPP is most frequently seen in association with PV, with about half of GPP patients presenting with both conditions [5]. PPPP is the most common variant of PP [3,4], with a prevalence of 0.050 to 0.12% [7]. The overall rarity and heterogeneity of PP presents challenges in uncovering its genetic basis, correlations between genotype and phenotype, and pathophysiology [3,5]. \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Disease** & **Clinical Morphology** & **Demographic** & **Pathology** & **Treatment** \\ \hline \hline \multirow{8}{*}{Generalized} & \multirow{8}{*}{All PP subtypes contain sterile pursulates [3].} & \multirow{8}{*}{Firth decade of life with slight female predominance [4].} & \multirow{8}{*}{Pathogenesis: Disruption of the interleukin-36 pathway plays a major role (mutations in IL36 RN), although there is significant heterogeneity in the gene pathways implicated [3,9,10].