Visual Diagnosis: An Acute Papular Eruption

A 5-year-old boy presents to the dermatology clinic for evaluation of a progressive rash that began two weeks ago. His mother reports that the rash initially appeared on his abdomen and then spread to his arms, legs and face. The lesions started as small pink-red bumps, which crusted and became scaly. The child is otherwise well with no fever, malaise or systemic symptoms. There is no mucosal involvement. The rash is minimally itchy, not painful, and no new products or medications have been introduced.

He was evaluated two days ago in the emergency department due to worsening of the rash and was thought to have pityriasis rosea. Over-the-counter antihistamines and topical hydrocortisone provided no improvement.

On examination, pink-red scaly papules coalescing into plaques are seen diffusely over the trunk, proximal more than distal extremities, and the neck. Many of these lesions over the buttocks and thighs are dark red to violaceous with overlying erosions and hemorrhagic crusting. Some of the lesions along the back appear to follow relaxed skin tension lines. There is relative sparing of upper face, scalp, medial buttocks and gluteal cleft. A skin biopsy was performed during the dermatology visit to help confirm the diagnosis.

Question 1

What is the most likely diagnosis in this patient?

1. Pityriasis rosea
   B. Guttate psoriasis
   C. Varicella (chickenpox)
   D. Pityriasis lichenoides et varioliformis acuta (PLEVA)
   E. Arthropod assault

Correct answer: D. Pityriasis lichenoides et varioliformis acuta (PLEVA)

Explanation:
This patient’s clinical features — an acute diffusely distributed papulosquamous eruption with eroded and crusted papules and minimal systemic symptoms — are most consistent with PLEVA, an uncommon inflammatory skin disorder in children. Lesions appear in successive crops, evolve from papules to crusted/ulcerated lesions, and often leave varioliform scars. A skin biopsy can help confirm the diagnosis and rule out other potential causes.

• A. Pityriasis rosea can present similarly with oval pink plaques and scale, often beginning with a herald patch and then spreading along relaxed skin tension lines, but it usually spares the face and is self-limited without the ulceration, crusting or scarring that is typically seen in PLEVA. PLEVA can be misdiagnosed, especially in the early stages before the lesions have developed their characteristic ulceration and crusting.
• B. Guttate psoriasis presents with small, red scaly papules often after streptococcal infection, but lesions are more monomorphic and lack the crusting or ulceration that is typical of PLEVA.
• C. Varicella progresses quickly from macules to vesicles and crusts, often accompanied by fever and systemic symptoms. Lesions are usually in various stages of evolution. PLEVA is not typically vesicular.
• E. Arthropod assault can cause crusted papules and excoriations but typically shows grouped distribution and intense pruritus and spares areas covered by clothing.

Question 2

Which of the following is the most appropriate first-line systemic treatment for moderate to severe PLEVA in a 5-year-old child?

1. 
   Oral acyclovir
   B. Oral erythromycin
   C. Systemic corticosteroids
   D. Topical calcineurin inhibitors

Correct answer: B. Oral erythromycin

Explanation:
While there are no treatments approved by the Food and Drug Administration for PLEVA, antibiotics with anti-inflammatory effects in the skin, such as oral erythromycin, azithromycin or doxycycline, are appropriate first-line systemic treatment for PLEVA. Erythromycin offers anti-inflammatory effects and is typically well tolerated in the pediatric population. In children under 8, tetracyclines like doxycycline are avoided due to risk of dental staining and bone effects, especially when the course of antibiotics is likely to be prolonged as is usual for PLEVA. The treatment is typically continued until the lesions have resolved, with courses typically lasting four weeks to three months and in some cases longer. Phototherapy with narrowband UVB

• A. Acyclovir is used for herpesvirus infections and has no role in PLEVA.
• C. Systemic corticosteroids have been employed in very severe cases of PLEVA, but data supporting their use is limited and they are not considered first line. Topical steroids can be helpful in the symptomatic treatment of PLEVA but are not appropriate monotherapy for the condition.
• D. Topical calcineurin inhibitors are not typically effective as monotherapy for PLEVA.

Question 3

Which of the following is a known severe variant/complication of PLEVA that may require hospitalization and systemic immunosuppression?

1. Post-streptococcal glomerulonephritis
2. Stevens-Johnson syndrome
3. Febrile ulceronecrotic Mucha-Habermann disease (FUHMD)
4. Toxic epidermal necrolysis
5. Lymphomatoid papulosis

Correct answer: C. Febrile ulceronecrotic Mucha-Habermann disease (FUHMD)

FUMHD is a rare but serious variant of PLEVA, marked by the development of rapidly progressing, painful necrotic papules and plaques, often with hemorrhagic crusts and high fever. Patients may become systemically ill.

Systemic symptoms can include fever, malaise, fatigue, lymphadenopathy, arthralgias, myalgias and hepatosplenomegaly.

Hospitalization is often necessary for systemic immunosuppressive therapy (e.g., corticosteroids, methotrexate), wound care and close monitoring. Prompt recognition is critical, as FUMHD may lead to life-threatening complications. Post-streptococcal glomerulonephritis, Stevens-Johnson syndrome, toxic epidermal necrolysis and lymphomatoid papulosis are not typically associated with PLEVA.

Clinical Pearls for Pediatricians

• PLEVA should be considered in the differential for persistent papulosquamous eruptions, particularly those with crusting or scarring.
• Lesions often present in crops and may be confused with pityriasis rosea, viral exanthems or early varicella.
• Systemic symptoms are uncommon in classic PLEVA but are a red flag for FUMHD.
• Erythromycin is a safe and effective first-line systemic option in young children.

Patient outcome:

The above patient was treated with azithromycin and began to improve within weeks of starting treatment. The medication was stopped after eight weeks of treatment due to his clinical response. At his most recent visit he was no longer developing new lesions and most of his eruption had healed with some residual post-inflammatory hypopigmentation and erythema.

References:

1. Reddy BY, et al. Pityriasis lichenoides: a review of pathogenesis and treatment. J Am Acad Dermatol. 2014;70(4):707.e1-707.e9.
2. Harper J, Oranje A, Prose N. Textbook of Pediatric Dermatology. 4th ed. Wiley-Blackwell; 2020.
3. Zaaroura H, et al. Febrile ulceronecrotic Mucha-Habermann disease: a review and update. Pediatr Dermatol. 2020;37(1):36-42.
4. Torrelo A. Pityriasis lichenoides in children. Semin Cutan Med Surg. 2010;29(3):146-150.
5. Weston WL, Lane AT, Morelli JG. Color Textbook of Pediatric Dermatology. 4th ed. Elsevier; 2007.