Biologic therapy increases Demodex density in psoriasis patients.

BACKGROUND: Demodex density is known to increase in various immunosuppressive conditions. The relationship between biologic therapy and Demodex density remains unknown. We aimed to investigate whether the density of Demodex mites is higher in psoriasis patients treated with biologic agents compared to treatment-naive or topically treated patients. METHODS: A cross-sectional study was conducted, comparing psoriasis patients receiving biologic therapy (n = 34) with controls (n = 33). Demodex density was assessed using the standardized skin surface biopsy technique (SSSB). Statistical analysis was performed to compare the densities and prevalence of demodicosis between the two groups. RESULTS: Demodex density was significantly higher in the biologic therapy group compared to the control group on the right cheek (7.29 vs. 0.12/cm2; P = 0.001), left cheek (8.15 vs. 0.24/cm2; P = 0.002), and whole face (average of all four regions: 5.50 vs. 0.80/cm2; P = 0.001). The prevalence of demodicosis was significantly higher in the biologic therapy group on the forehead (35.3% vs. 12.1%; P = 0.043), right cheek (41.2% vs. 0%; P < 0.001), and left cheek (44.1% vs. 0%; P < 0.001). The frequency of cases with demodicosis in at least one localization was higher in the biological therapy group compared to the control group (61.8% vs. 15.2%; P < 0.001). CONCLUSIONS: Psoriasis patients receiving biologic therapy had a higher Demodex density and prevalence of demodicosis compared to controls. Biologics may lead to an increase in Demodex density by blocking specific cytokines, such as interleukin-17 and tumor necrosis factor-α, which play a role in immunity against Demodex. Further research is needed to explore the impact of different biological agents on Demodex density.

The effect of phototherapy on Demodex density: a case-control study.

BACKGROUND: Human Demodex mites, Demodex folliculorum and Demodex brevis, are microorganisms that reside in the pilosebaceous units, usually without causing symptoms. Phototherapy has been linked to demodicosis in previous studies. We aimed to determine whether there was an increase in the frequency of demodicosis and Demodex density after 20 phototherapy sessions. METHODS: A case-control study was conducted with 32 participants who received narrowband ultraviolet B or ultraviolet A-1 therapy for various dermatological indications. Standardized skin surface biopsies were performed before and after phototherapy to assess Demodex density. The presence of Demodex-related skin conditions was assessed before phototherapy. A statistical analysis was performed to compare the Demodex densities and prevalence of demodicosis between the baseline and 20th session of phototherapy. RESULTS: No significant change was observed in Demodex density after 20 sessions of phototherapy. The average Demodex density before treatment was 2.75 ± 4.48 (/cm2 ), and after treatment, it was 2.85 ± 4.81 (/cm2 ), indicating no significant difference (P = 0.879). The percentage of patients with demodicosis in at least one region of the face was 28.1% (9/32) before treatment, and after treatment, it was 31.3% (10/32), with no significant difference (P = 1.00). CONCLUSIONS: Our findings contradict previous studies that suggested an increased Demodex density and demodicosis prevalence after phototherapy. The data from previous studies are open to debate due to their selected samples, designs, and interpretations regarding the phototherapy-immunosuppression-Demodex relationship. Larger-scale longitudinal studies conducted on a homogeneous sample are warranted to better understand the relationship between phototherapy and demodicosis.

An unusual case of sporotrichoid nodules: metastatic cutaneous squamous cell carcinoma.

A 63-year-old immunocompetent patient presented with a 4 month history of 12 painless nodules in a linear array on his right arm. He had a history of a surgery for a cutaneous tumor on the dorsum of his right middle finger about a year prior, but he did not follow up after the surgery. A differential diagnosis of sporotrichosis, atypical mycobacteria, deep fungal infection, and metastatic cutaneous squamous cell carcinoma (SCC) was considered. Skin biopsy revealed islands of dysplastic squamous cells and keratin pearls in a desmoplastic stroma in the deep dermis and subcutaneous tissue. The behavior of the disease was very aggressive, with rapid dissemination in a linear array, mimicking an infectious sporotrichoid spread. To our knowledge, this is the second case report of sporotrichoid metastases to the skin from cutaneous SCC in an immunocompetent patient.