# Pustular psoriasis: From Pathophysiologyology to Treatment
### Clinical Variants
#### 2.1.3 Annular Pustular Psoriasis  
Circinate or annular PP is a rare variant, consisting in an erythematous eruption with annular or polycyclic lesional morphology, small sterile pustules at the periphery of the lesions, and fine desquamation with mild-to-no systemic symptoms. Usual sites of involvement are flexural areas of the trunk and proximal extremities, buttocks and abdomen [41]. Formerly included within the spectrum of GPP, it is now considered a  
\begin{table} \begin{tabular}{p{142.3 pt} p{284.5 pt}} \hline \hline Main features of AGEP & Rare disorder attributed mostly to drugs (infections, hypersensitivity to mercury and spider bite have sporadically been implicated) \\ Main features of AGEP & Sudden occurrence of a generalized skin rash with sterile nonfollicular pinhead-sized pustules on an oedematous erythema, often associated with systemic symptoms, including fever, leucocytosis and neutrophil \\  & Spontaneous resolution of pustules within a few days followed by pin-point desquamation \\  & Mild, nonerosive mucous membrane involvement (mostly oral) in about 20\% of cases \\ \hline  & Absence of family/personal history of psoriasis (however, history of psoriasis possible in AGEP) \\  & Recent drug administration (very frequent in AGEP, possible but less frequent in GPP, that can also be drug-elicited) \\  & Predominance of lesions in the folds, especially at the onset \\  & Shorter duration of fever and pustules \\  & Spontaneous rapid resolution (within 15 days after withdrawal of the culprit drugs) and \\ Factors favoring the diagnosis of AGEP & Arthritis (rare in AGEP, affecting about 30\% of cases in GPP) \\ over GPP & Peripheral eosinophil (present in about one-third of cases and usually mild) \\  & Histopathological features: \\  & - & superficial spongiform pustules, exocytosis of neutrophils and eosinophils, occasional necrotic keratinocytes, papillary dermal oedema, mixed dermal infiltrates containing neutrophils and eosinophils (classical psoriasis changes infrequent and usually mild) \\  & - & presence of eosinophils, absence of PDCs and absence of tortuous dilated capillaries favoring a diagnosis of AGEP over PP (perivascular and intraepidermal PDCs, dilated tortuous vessels and MxA expression in the dermal inflammatory infiltrate significantly in favor of PP) \\ \hline Information extracted from References [2; 21; 22; 23; 24]. AGEP: acute generalized exanthematous pustulosis; GPP: generalized pustular psoriasis; MxA: human myxovirus resistance protein 1; PDCs: plasmacytoid dendritic cells; PP: pustular psoriasis. \\ \hline \hline \end{tabular}   
* Von Zumbusch psoriasis may exhibit an unfavourable prognosis, especially in cases evolving from ACH [1; 29]. Mortality in GPP has mostly been attributed to complications resulting from sepsis, acute respiratory distress syndrome and cardiac failure [14]. Secondary amyloidosis is mentioned as another potential complication of GPP [30]. * Impetigo Herpetiformis (Pustular Psoriasis of Pregnancy)
* IH is a form of pregnancy-associated PP first described in 1872 by [PERSON] [31]. It is controversial whether this entity should be considered distinct from PP [32; 33]. It is most frequently observed in the last trimester of pregnancy [34]. Multiple sterile pustules on an erythematous base are observed in an annular configuration at the folds with subsequent spreading over the body [34; 35]. Systemic symptoms, such as fever, chills, fatigue, nausea, diarrhea, and polyarthalgias, may be observed [32; 33; 34]. Leukocytosis with neutrophic predominance, anemia, increased erythrocyte sedimentation rate, hypoclcemia, hypophosphatemia and hypoalbuminemia are notable laboratory findings [33; 35]. IH, especially if severe and long-lasting, may lead to poor neonatal outcomes, including placental insufficiency, fetal abnormalities, stillbirth, and early neonatal death [36], as well as to maternal death [31]. Most patients experience prompt remission in the post-partum period [37; 38].