63916 Idiopathic CD4+ T Cell lymphocytopenia associated with a chronic recalcitrant erythroderma resembling pityriasis rubra pilaris

Document Type

Conference Proceeding

Publication Date

9-1-2025

Publication Title

J Am Acad Dermatol

Abstract

A 75-year-old male presented with a rapidly spreading papulosquamous eruption that progressed to exfoliative erythroderma involving his entire skin surface. Despite various treatments, his condition remained recalcitrant, leading to frequent reconsideration of the diagnosis. Punch biopsy showed an acanthotic epidermis with parakeratosis alternating with orthokeratosis, focal follicular plugging, and spongiosis. T-cell receptor gene rearrangement studies revealed a dominant clonal population of T cells that did not match previous clones found in the skin, blood, and lymph nodes. Laboratory findings included low CD4+ T-cell counts and low CD4/CD8 ratios. Bone marrow biopsy showed normocellular marrow without evidence of T-cell lymphoproliferative disorder. Next-generation sequencing revealed clonal hematopoiesis of indeterminate potential and an acquired Tet2 mutation. Tet2 deletion in CD4+ T cells was shown to disrupt Th1 lineage commitment, potentially causing imbalances in CD4+ T-cell subsets. This disruption is suspected to impair adaptive immunity, leading to secondary immuno-dysregulation in the skin. This case may represent the first instance of pityriasis rubra pilaris as a primary manifestation of idiopathic CD4+ T-cell lymphocytopenia (ICL), a rare syndrome characterized by persistently low CD4+ T lymphocyte counts unrelated to HIV. ICL is associated with various immune defects, including reduced proliferative responses to homeostatic cytokines, reduced T cell receptor repertoire (as seen in this case, with multiple varying mono-/oligoclonal T-cell expansions in the skin, blood, and lymph nodes), altered chemotaxis due to impaired chemokine receptor expression, dysfunctional tyrosine kinase activity disrupting T cell receptor signaling, and increased apoptosis due to upregulation of CD95 expression.

Volume

93

First Page

AB52

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