Dermatology MCQ - Inflammatory Dermatoses - PUSTULAR PSORIASIS

A 40-year-old woman in her 30th week of pregnancy presents with the sudden onset of widespread, sterile pustules on an erythematous base, predominantly in her flexures and trunk. She has a high fever and leukocytosis. A biopsy of a pustule shows spongiform pustules of Kogoj. She has no prior history of psoriasis. Which of the following is the most likely diagnosis and the most appropriate initial treatment?

A) Impetigo herpetiformis; systemic corticosteroids
B) Generalized pustular psoriasis; systemic corticosteroids
C) Acute generalized exanthematous pustulosis (AGEP); discontinuation of the culprit drug
D) Subcorneal pustulosis (Sneddon-Wilkinson disease); dapsone
E) Candidiasis; systemic antifungals

Correct Answer: A) Impetigo herpetiformis; systemic corticosteroids

Explanation

This presentation is classic for impetigo herpetiformis, which is now considered synonymous with generalized pustular psoriasis of pregnancy (PPP). It is a rare, severe dermatosis of pregnancy.

Key Clinical Features:

• Timing: Typically occurs in the third trimester of pregnancy.

• Presentation: Sudden eruption of widespread, sterile pustules on a background of fiery erythema, often starting in flexural areas (groin, axillae) and becoming generalized.

• Systemic Symptoms: High fever, malaise, diarrhea, and leukocytosis are common and reflect the systemic inflammatory nature of the disease.

• Histopathology: The finding of spongiform pustules of Kogoj (collections of neutrophils within the epidermis) is the hallmark of all forms of pustular psoriasis, confirming the diagnosis.

Why It's Impetigo Herpetiformis/PPP and Not Standard GPP:

While the disease is pathophysiologically identical to generalized pustular psoriasis (GPP), the specific context of pregnancy and the historical name "impetigo herpetiformis" are used. This distinction is crucial because management must consider the fetus.

Most Appropriate Initial Treatment:

• Systemic Corticosteroids (e.g., prednisone 0.5-1 mg/kg/day) are the first-line treatment.

  • Rationale: They act quickly to control the severe inflammation and are relatively safe in pregnancy, especially compared to other systemic agents for psoriasis.

  • They are often very effective in controlling the disease until delivery.

Why Not the Other Options?

• (B) Generalized pustular psoriasis: This is the correct pathophysiological diagnosis, but in the specific context of pregnancy, the term impetigo herpetiformis or PPP is applied. The treatment (systemic corticosteroids) is the same, making this a very close second choice. However, option A is more precise for the clinical scenario.

• (C) Acute generalized exanthematous pustulosis (AGEP): A severe drug reaction that mimics PPP. However, it typically occurs within 48 hours of drug administration and histology may show eosinophils. The lack of a drug history and the pregnancy context make PPP more likely.

• (D) Subcorneal pustulosis (Sneddon-Wilkinson disease): A chronic, relapsing condition with flaccid, subcorneal pustules in a "serpiginous" pattern. It lacks the systemic symptoms and the histology shows subcorneal pustules, not spongiform pustules.

• (E) Candidiasis: Would show pseudohyphae and yeast on KOH preparation or biopsy, and pustules would not be sterile.

Critical Complications:
This condition poses significant risks to both mother and fetus, including:

• Placental insufficiency

• Fetal distress

• Stillbirth

Management and Prognosis:

• Treatment often requires hospitalization.

• The disease typically resolves rapidly after delivery but may recur in subsequent pregnancies.

• Other agents like cyclosporine can be considered if corticosteroids fail.

Note: "Impetigo herpetiformis" is a misnomer (it is not infectious nor herpetic) but remains in use for this specific presentation of GPP in pregnancy. The key is to recognize this as a dermatologic emergency in pregnancy requiring prompt treatment with systemic corticosteroids to reduce maternal and fetal morbidity.