Histopathologic and Clinical Findings Distinguish Acute Generalized Exanthematous Pustulosis From Pustular Psoriasis

Pustular psoriasis of pregnancy (PPP) is a rare, life-threatening disease.8 It is sometimes referred to as impetigo herpetiformis, but many dermatologists consider this a misnomer because PPP is not associated with the herpes virus or bacterial infection.8 Although it is unclear whether PPP is specific to pregnancy, it typically arises early in the third trimester in affected women.3,8 Sterile erythematous plaques studded by painful pustules originate in skin folds on the trunk and back before coalescing into large dry desquamating plaques that spread to the extremities.2,8 Symptoms include fever, nausea, and diarrhea. Patients may also have neutrophilia, electrolyte abnormalities, and elevated inflammatory markers.2,8 Aggressive treatment is required and usually consists of systemic corticosteroids.8 Untreated PPP can lead to placental insufficiency, intrauterine growth restriction, and even miscarriage or stillbirth.8 Pregnant women with PPP and their fetuses should be closely monitored.2,8

Pustular psoriasis of pregnancy (PPP) is a rare, life-threatening disease.8 It is sometimes referred to as impetigo herpetiformis, but many dermatologists consider this a misnomer because PPP is not associated with the herpes virus or bacterial infection.8 Although it is unclear whether PPP is specific to pregnancy, it typically arises early in the third trimester in affected women.3,8 Sterile erythematous plaques studded by painful pustules originate in skin folds on the trunk and back before coalescing into large dry desquamating plaques that spread to the extremities.2,8 Symptoms include fever, nausea, and diarrhea. Patients may also have neutrophilia, electrolyte abnormalities, and elevated inflammatory markers.2,8

Aggressive treatment is required and usually consists of systemic corticosteroids.8 Untreated PPP can lead to placental insufficiency, intrauterine growth restriction, and even miscarriage or stillbirth.8 Pregnant women with PPP and their fetuses should be closely monitored.2,8

Clinical and histopathologic findings may differentiate acute generalized exanthematous pustulosis from pustular psoriasis.

Eosinophilic spongiosis, vacuolar interface dermatitis, dermal eosinophilia, mucosal involvement, psoriasis history, and the presence of scaling plaques can help differentiate acute generalized exanthematous pustulosis (AGEP) and pustular psoriasis, study findings published in the Journal of the American Academy of Dermatology suggest.

A total of 22 cases of AGEP and 11 cases of pustular psoriasis were identified from the laboratory information system at the dermatology department of the University of Florida in Gainesville. Clinical and histopathologic features of each case were reviewed to identify features that could reliably distinguish AGEP from pustular psoriasis. In addition, the researchers performed an immunohistochemistry panel consisting of PHH3, CD3, CD4, CD8, CD161, and FOXP3.

Histopathologic findings that were most common for AGEP vs pustular psoriasis were eosinophilic spongiosis (P =.018), vacuolar interface dermatitis (P =.010), and dermal eosinophilia (P =.003). Conversely, pustular psoriasis was favored by dermal CD161 positivity with a threshold of 10 positive cells per punch biopsy vs AGEP (P <.001). The researchers did not find FOXP3 helpful in distinguishing between the 2 disorders. Mucosal involvement was a clinical feature that was unique to AGEP despite its lack of significance. Clinical features that distinguished pustular psoriasis from AGEP included psoriasis history (P <.001) and the presence of scaling plaques (P =.005).

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Study limitations included the small sample size, as well as the inclusion of retrospective laboratory data from a single center.

Findings from this study indicate that “a combination of clinical and histopathologic findings is helpful in differentiating AGEP from [pustular psoriasis],” the researchers concluded.

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Reference

Isom J, Braswell DS, Siroy A, Auerbach J, Motaparthi K. Clinical and histopathologic features differentiating acute generalized exanthematous pustulosis and pustular psoriasis: a retrospective series [published online March 12, 2020]. J Am Acad Dermatol. doi: 10.1016/j.jaad.2020.03.015