Differential Diagnosis

• Single most likely diagnosis
  • A) Eczema herpeticum: This is the most likely diagnosis due to the presence of painful umbilicated vesicles at sites of active skin inflammation, which is characteristic of eczema herpeticum, a complication of atopic dermatitis (eczema) caused by a herpes simplex virus infection. The patient's history of allergy to pollen and dust, and the examination findings of patches of erythema with mild lichenification, also support a diagnosis of atopic dermatitis.
• Other Likely diagnoses
  • E) Pityriasis rosea: Although less likely, pityriasis rosea could be considered due to the presence of erythema and vesicles. However, the typical herald patch and distribution of lesions in a "Christmas tree" pattern are not mentioned.
  • B) Herpes zoster: This could be a consideration for the painful vesicles, but the distribution and the presence of underlying skin inflammation make it less likely.
• Do Not Miss (ddxs that may not be likely, but would be deadly if missed.)
  • None of the options provided fit perfectly into this category, but it's essential to consider other conditions that could present with similar symptoms, such as:
    • Staphylococcal scalded skin syndrome (SSSS): Although rare in adolescents, SSSS is a serious condition caused by staphylococcal toxins that could present with skin inflammation and vesicles.
    • Autoimmune bullous diseases: Conditions like pemphigus or pemphigoid could present with vesicles and skin inflammation, although they are less common and typically have distinct features.
• Rare diagnoses
  • C) Keratosis pilaris: This condition presents with small, rough, sandpapery bumps on the skin, typically on the arms, legs, or buttocks, but it does not usually include vesicles or significant erythema.
  • D) Lichen planus: Characterized by purplish, itchy, flat bumps, lichen planus can sometimes present with vesicles, but the description provided does not closely match the typical presentation of lichen planus.