Discussion: Pityriasis Lichenoides in Children

Pityriasis lichenoides (PL) is a cutaneous disease of unknown etiology. It is classified into an acute form, pityriasis lichenoides et varioliformis acuta (PLEVA), and a chronic form, pityriasis lichenoides chronica (PLC). Most experts believe these presentations are variants of the same condition that exist on a spectrum and have significant clinical and histologic overlap.1 Approximately 20% of PL cases are seen in children; the average age of onset during childhood is 6.5 years.1 

Clinical Presentation

PLEVA presents with an abrupt onset of recurrent 2- to 3-mm erythematous macules and papules that often become hemorrhagic, crusted, or vesicular.1 Lesions of PLEVA most commonly develop on the trunk and extremities, with less extensive involvement seen on the head, neck, palms, or soles. 

PLC presents with a gradual onset of erythematous papules and plaques, often with centrally adherent scale. As in PLEVA, the trunk and extremities are commonly involved.1 Children with both forms of PL are more likely than adults to have widespread lesions, including lesions on the head and neck.2


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Pathophysiology

The exact pathophysiologic mechanism of PL remains to be elucidated. A significant number of childhood case reports show an association with a viral illness, vaccination, or an autoimmune or autoinflammatory disorder, which supports the etiologic theory of an inflammatory response to an antigenic trigger.1

Diagnosis

The diagnosis of PL can be made clinically with histopathologic confirmation. Lesions of PLEVA often have a wedge-shaped superficial and deep perivascular lymphocytic infiltrate with an intense vacuolar interface dermatitis, owing to its acute nature. In PLEVA, there is evidence of epidermal changes, with transepidermal extravasation of erythrocytes as well as vesiculation, spongiosis, ulcerations, and/or necrotic keratinocytes. PLC has a sparser lymphocytic infiltrate with mild vacuolar interface dermatitis and more subtle epidermal changes, with a primarily orthokeratotic, nonacute stratum corneum. 

Treatment

There are no formal therapeutic standards for PL, and efficacy data on pediatric treatment are generally limited to retrospective studies and case reports. 

Topical corticosteroids may relieve the pruritus sometimes associated with PL but have little effect on the lesions.Various oral antibiotics have been investigated, and erythromycin at a dosage of 30 to 50 mg/kg/d in divided doses is generally recommended.4 In a study of 24 children with PL (62.5% with PLC), 64% of patients had a good response after 1 month of erythromycin treatment, 73% had a good response after 2 months of treatment, and 83% had a good response after 3 months of treatment.4 These results suggest that erythromycin should be continued for at least 3 months to avoid risk for recurrence. Erythromycin is thought to be efficacious in the treatment of PL because of its anti-inflammatory effects. Other antibiotics that have been used based on anecdotal evidence include azithromycin, doxycycline (in children older than 8 years old), the cephalosporins, and amoxicillin-clavulanic acid.   

Narrowband ultraviolet B phototherapy has been shown to be effective and well tolerated in children with PL.5,6 The mechanism of action is thought to be depletion of T cells in inflamed skin lesions through the modification of cytokines. Treatment courses range from 8 to 16 weeks.

Systemic immunosuppressants such as methotrexate and cyclosporine have been used but should only be considered in severe cases that are unresponsive to other forms of treatment because of the significant adverse effects associated with these drugs.3

Prognosis

PLC has a relapsing and remitting course and may persist for months or even years.1 In a retrospective review of 124 cases of PL in children, the median duration of PLC was 20 months.7 The same study showed a 77% recurrence rate over 10 years. Clinical resolution of both PLC and PLEVA eruptions is often followed by postinflammatory pigmentary changes. Hypopigmentation is more likely to be seen in darker skin types and in children.2

The possibility that PL exists on a spectrum with T-cell lymphoproliferative disorders is controversial and remains under investigation.1 Rare case reports have linked childhood PL to the development of cutaneous T-cell lymphoma; therefore, it is recommended that children with PL be monitored routinely for changes in cutaneous disease. 

Case Conclusion

The current patient was treated with oral erythromycin. She experienced improvement after 1 month of therapy and tolerated discontinuation of the medication after 2 months. 

References

  1. Geller L, Antonov NK, Lauren CT, Morel KD, Garzon MC. Pityriasis lichenoides in childhood: review of clinical presentation and treatment options. Pediatr Dermatol. 2015;32:579-592.
  2. Wahie S, Hiscutt E, Natarajan S, Taylor A. Pityriasis lichenoides: the differences between children and adults. Br J Dermatol. 2007;157:941-945.
  3. Paller AS, Mancini AJ. Papulosquamous and related disorders. In: Hurwitz Clinical Pediatric Dermatology. 5th ed. New York: NY: Elsevier; 2015:73-94.
  4. Hapa A, Ersoy-Evans S, Karaduman A. Childhood pityriasis lichenoides and oral erythromycin. Pediatr Dermatol. 2012;29:719-724.
  5. Maranda EL, Smith M, Nguyen AH, Patel VN, Schachner LA, Joaquin JJ. Phototherapy for pityriasis lichenoides in the pediatric population: a review of the published literature. Am J Clin Dermatol. 2016;17:583-591.
  6. Ersoy-Evans S, Altaykan A, Sahin S, Kölemen F. Phototherapy in childhood. Pediatr Dermatol. 2008;25:599-605.
  7. Ersoy-Evans S, Greco MF, Mancini AJ, Subaşi N, Paller AS. Pityriasis lichenoides in childhood: a retrospective review of 124 patients. J Am Acad Dermatol. 2007;56:205-210. 

Images courtesy Marisa Wolff, MD.