The following is a summary of “Single cell sequencing delineates T-cell clonality and pathogenesis of the parapsoriasis disease group,” published in the September 2024 issue of Allergy and Immunology by Alkon et al.
Mycosis fungoides (MF) is often underdiagnosed due to its similarity to benign dermatoses like atopic dermatitis (AD). The distinction between MF and parapsoriasis en plaque remains controversial.
Researchers conducted a retrospective study to characterize the parapsoriasis disease spectrum.
They used single-cell RNA sequencing on skin biopsies from patients with parapsoriasis-to-early-stage MF, stratified by plaque size. They compared them to AD, psoriasis, and healthy control skin.
The results showed that 6 out of 8 large-plaque lesions harbored an expanded alpha/beta or gamma/delta T-cell clone with CD7 downregulation, consistent with early-stage MF. In contrast, 6 out of 7 small-plaque lesions were polyclonal, lacking a lymphomatous phenotype, and displayed a less inflammatory microenvironment than early-stage MF or AD. Polyclonal small- and large-plaque lesions harbored NPY+ innate lymphoid cells and showed a stromal signature with complement upregulation and antimicrobial hyperresponsiveness in fibroblasts and sweat gland cells. These conditions were distinct from AD (CD3 + CRTH2 + IL13 -expressing “Th2A” cells) or psoriasis (type 17 inflammation).
Investigators concluded that polyclonal small- and large-plaque dermatitis lesions represent a distinct disease entity with a unique ILC population. They proposed the term “polyclonal parapsoriasis en plaque” based on clear differentiation from MF, psoriasis, and AD at cellular and molecular levels.
Source: jacionline.org/article/S0091-6749(24)00942-4/fulltext
