Late-Onset Bexarotene-Induced CD4 Lymphopenia in a Cutaneous T-cell Lymphoma Patient

Infections, autoimmune disease, bone marrow failure, medications, and total-body irradiation may induce CD4 lymphopenia, defined as a CD4 T-cell count below 300 cells/mL or less than 20% of total lymphocytes.¹ Human immunodeficiency virus (HIV) is the most common cause of CD4 lymphopenia, with sepsis (bacterial and fungal) and postoperative states the most common causes in hospital settings.² No underlying factors are found in 0.02% of CD4 lymphopenia cases, which are considered to be idiopathic.^3,4 We report a patient with cutaneous T-cell lymphoma (CTCL) who developed profound CD4 lymphopenia in the setting of long-term bexarotene therapy.

Case Report

A 63-year-old man with hypertension presented to our dermatology clinic with pruritic scaly plaques on the scalp of 4 months’ duration that had progressed to full-body exfoliative erythroderma (Figure 1). He had diffuse palmoplantar keratoderma and lymphadenopathy. His only long-term medications were terazosin for benign prostatic hyperplasia and atenolol for hypertension; he reported no new medications. Laboratory evaluation revealed normal liver and kidney function. A complete blood cell count (CBC) revealed a white blood cell (WBC) count within reference range (8000/µL [reference range, 4500–11,000/µL]) but with increased eosinophils (12.9% [reference range, 2.7%]) and monocytes (11.8% [reference range, 4%]) and reduced lymphocytes (16.8% [reference range, 34%]). Flow cytometry showed a CD4:CD8 ratio of 1.18 to 1 (reference range, 0.8–4.2)(absolute CD4⁺ cells, 764/µL [reference range, 297–1551/µL]; absolute CD8⁺ cells, 654/µL [reference range, 100–1047/µL]). Skin biopsy revealed subacute spongiotic dermatitis with numerous eosinophils, exocytosis including folliculotropism, and rare atypical lymphocytes (Figure 2). Molecular studies showed T-cell receptor γ gene rearrangement. The patient did not have any other underlying conditions that would predispose him to lymphopenia. Based on these findings, a diagnosis of CTCL stage IIIA was made and agreed on by experts at the University of California, San Diego Dermatology Grand Rounds.

Figure 1. Exfoliative erythroderma at initial presentation.

Figure 2. Skin biopsy at initial diagnosis revealed subacute spongiotic dermatitis with numerous eosinophils, exocytosis including folliculotropism, and rare atypical lymphocytes (H&E, original magnification ×10).