A case series of 22 children revealed a mean duration in pityriasis lichenoides et varioliformis acuta of 1.6 months to complete resolution and a mean duration in pityriasis lichenoides chronica of 7.5 months.[33]Romani J, Puig L, Fernandez-Figueras MT, et al. Pityriasis lichenoides in children: clinicopathologic review of 22 patients. Pediatr Dermatol. 1998 Jan-Feb;15(1):1-6.
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The natural tendency of the disease is to remit spontaneously, but some cases may wax and wane over years. Disease duration may be longer in adults.
Recurrent and chronic
Even though pityriasis lichenoides is an inflammatory benign skin disorder, it can be chronic, unpredictable and stubborn to respond to therapies. In order to ensure appropriate care, close and regular follow-up is recommended.[1]Khachemoune A, Blyumin ML. Pityriasis lichenoides: pathophysiology, classification, and treatment review. Am J Clin Dermatol. 2007;8(1):29-36.
http://www.ncbi.nlm.nih.gov/pubmed/17298104?tool=bestpractice.com
Evolution to skin lymphoma
There are several reports that all forms of pityriasis lichenoides can transform into cutaneous lymphoma (mycosis fungoides).[1]Khachemoune A, Blyumin ML. Pityriasis lichenoides: pathophysiology, classification, and treatment review. Am J Clin Dermatol. 2007;8(1):29-36.
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[4]Bowers S, Warshaw EM. Pityriasis lichenoides and its subtypes. J Am Acad Dermatol. 2006 Oct;55(4):557-72; quiz 573-6.
http://www.ncbi.nlm.nih.gov/pubmed/17010734?tool=bestpractice.com
Therefore, regular follow-up re-evaluations are recommended, even if the eruption has resolved, to monitor for any changes or new eruptions.[4]Bowers S, Warshaw EM. Pityriasis lichenoides and its subtypes. J Am Acad Dermatol. 2006 Oct;55(4):557-72; quiz 573-6.
http://www.ncbi.nlm.nih.gov/pubmed/17010734?tool=bestpractice.com
Should the skin eruption change or recur in a different presentation, skin biopsy must be done to evaluate for potential malignancy.[1]Khachemoune A, Blyumin ML. Pityriasis lichenoides: pathophysiology, classification, and treatment review. Am J Clin Dermatol. 2007;8(1):29-36.
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Furthermore and as a precaution, assessment of the review of systems such as fever and weight loss may assist in ruling out the paraneoplastic potential.
Febrile ulceronecrotic Mucha-Habermann disease variant
The ulceronecrotic form of pityriasis lichenoides should be urgently treated with multidisciplinary approach and likewise closely monitored for complete resolution and potential recurrence.[1]Khachemoune A, Blyumin ML. Pityriasis lichenoides: pathophysiology, classification, and treatment review. Am J Clin Dermatol. 2007;8(1):29-36.
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[19]Cozzio A, Hafner J, Kempf W, et al. Febrile ulceronecrotic Mucha-Habermann disease with clonality: A cutaneous T-cell lymphoma entity? J Am Acad Dermatol. 2004 Dec;51(6):1014-7.
http://www.ncbi.nlm.nih.gov/pubmed/15583604?tool=bestpractice.com
Mortality is around 20%; factors associated with a poorer prognosis include increased age, systemic involvement, and monoclonal T-cell receptor rearrangement.[1]Khachemoune A, Blyumin ML. Pityriasis lichenoides: pathophysiology, classification, and treatment review. Am J Clin Dermatol. 2007;8(1):29-36.
http://www.ncbi.nlm.nih.gov/pubmed/17298104?tool=bestpractice.com
[34]Tasouli-Drakou V, Nguyen M, Guinn H, et al. Mortality risk factors in febrile ulceronecrotic Mucha- Habermann disease: a systematic review of therapeutic outcomes and complications. Dermatol Reports. 2022 Nov 21;14(4):9492.
https://www.pagepress.org/journals/dr/article/view/9492/8834
http://www.ncbi.nlm.nih.gov/pubmed/36483219?tool=bestpractice.com