Next‐generation sequencing confirms T‐cell clonality in a subset of pediatric pityriasis lichenoides

Abstract

Background Pityriasis lichenoides (PL) is a papulosquamous disease that affects both adults and children. Previous studies have shown a subset of this entity to have clonal T‐cell populations via PCR‐based assays. In this study, we sought to implement next‐generation sequencing (NGS) as a more sensitive and specific test to examine for T‐cell clonality within the pediatric population. Methods We identified 18 biopsy specimens from 12 pediatric patients with clinical and histopathologic findings compatible with PL. Patient demographics, clinical features, management, and histopathologic findings were reviewed. All specimens were analyzed for clonality with NGS of T‐cell receptor beta (TRB) and gamma (TRG) genes. Results Of the 12 patients, 9 (75%) had complete resolution of lesions at the time of data collection (mean follow‐up 31 months). The remaining three patients significantly improved with methotrexate (with or without acitretin). Interestingly, 7 of 12 patients (58%) and 9 of 17 biopsy specimens (53%) showed evidence of T‐cell clonality. Two patients showed matching TRB clones from different anatomic sites. Conclusions T‐cell clonality is a common finding in PL, probably representing a “reactive clonality” rather than a true lymphoproliferative disorder. Clonality alone cannot be used as a means to distinguish PL from lymphomatoid papulosis or cutaneous lymphoma.

Type D lymphomatoid papulosis with pityriasis lichenoides et varioliformis acuta-like features in a child with parvovirus infection: a controversial diagnosis in the spectrum of lymphoid proliferations: case report and literature review

“…Furthermore, the clearcut defective T-cell phenotype may overlap the features of the atypical variant of pityriasis lichenoides, from which our case stands apart on the ground of cytologic pleomorphism and, most importantly, CD30 expression [ 12 ]. Not helpful for a differential diagnosis, TCRG clonality can be consistent either with a WHO-defined T-cell lymphoproliferative disorder or with an antigen-driven, cytotoxic CD8 + T-cell expansion [ 13 , 14 ]. In our case, the documentation of a clonal peak constitutes a further—albeit weak—indication in support of a LyP-type process, and prospectively, it serves as the benchmark for further monitoring the disease in the contingency of a relapse.…”

Interface change in early mycosis fungoides: A potential mimicker of benign dermatoses

“…PL, encompassing the spectrum of PLEVA and pityriasis lichenoides chronica, is a benign entity that can exhibit “reactive” T‐cell clonality and show overlapping histopathologic features with MF 23–26 . In contrast to MF, PL presents clinically as a papular eruption of smaller lesions, with a natural course towards spontaneous resolution.…”

Utility of IL‐36 immunostaining in distinguishing psoriasis from pityriasis rosea and pityriasis lichenoides

“…17 The etiology of PL remains unclear, though several hypotheses exist in the literature, including an inflammatory response to infection, an immune-complex mediated hypersensitivity vasculitis, and an indolent T-cell lymphoproliferative disorder that can show T-cell monoclonality. [18][19][20][21][22][23][24][25][26][27] In any case, IL-36 does not appear to be a significant driver of inflammation in most cases of this disease.…”