Assessment of Blue Light Phototherapy for Grover Disease

Abstract

This nonrandomized clinical trial assesses treatment of patients diagnosed with Grover disease with blue light phytotherapy for several weeks.

Transient acantholytic dermatosis, or Grover disease, is a relatively uncommon skin disorder characterized by pruritic papulovesicular eruptions of truncal skin. Grover disease is theorized to develop from thermal insults of eccrine sweat ducts leading to their subsequent occlusion.^1,2 Treatments, including topical steroids (first-line), topical retinoids or calcipotriene, isotretinoin, and narrowband UV-B phototherapy (NBUVB) are often suboptimal.² We hypothesized that blue light therapy—treatment used for actinic keratoses, hemolytic jaundice of the neonate, and psoriasis—may also be beneficial for treatment of Grover disease.

Methods

This nonrandomized controlled trial was conducted at Northwestern University (Chicago, IL). The protocol was approved by the Northwestern University institutional review board and registered at ClinicalTrials.gov (NCT04343586). All participants provided written informed consent.

Adult patients with an International Statistical Classification of Diseases and Related Health Problems, Tenth Revision (ICD-10) diagnosis of Grover disease were eligible. Participants completed a 2-week washout during which no therapies were used. All participants underwent 15 treatments of nonionizing blue light phototherapy irradiation with an FDA cleared, commercially available blue light system without photosensitization. Sessions lasted 9 minutes per side, 3 times per week for 5 consecutive weeks (cumulative dosage = 180 J/cm²). Two blinded observers (M.O. and D.M.) determined clinical status by lesion counts from clinical photographs at study baseline and conclusion. Changes in lesion count, serum concentrations of TNF-α, C-reactive protein, IL-12p40, IFN-γ, Dermatology Life Quality Index, and 12-item Itch Severity Scale pretreatment and posttreatment were compared with paired t test and Wilcoxon rank sum tests, and significance was set at P < .05, 2-sided. Further information is available in the eMethods in the Supplement.

Results

Eleven patients (9 men and 2 women, mean [SD] age, 63 [14] years) were enrolled. One participant did not complete treatment and was excluded. Participants experienced treatment failure with a median of 2 prior pharmacological therapies, and only 2 participants reported prior disease remission. Overall, 7 patients previously used topical steroids (most commonly triamcinolone or betamethasone), 1 used tretinoin cream, and others used over-the-counter topicals for symptomatic relief (Table).

Table. Patient Demographic Characteristics.

Characteristic	No. (%)
Consented, total No.	11
Completed study	10 (91)
Did not complete study	1 (9)
Age, mean (SD), y	63 (14)
Sex
Men	9 (82)
Women	2 (18)
Race and ethnicitya
White	11 (100)
Duration of disease, mean (SD), y	3.4 (2.5)
No. of prior therapies, mean (SD)	2 (1.5)

^a Patient race and ethnicity designation was determined by patient self-report.

Mean baseline lesion count decreased from 27 (95% CI, 9.2-45.6) to 6 (95% CI, 2.5-8.7; P = .007) (Figure). Itch Severity Scale decreased from 7.8 (95% CI, 6.5-8.9) to 5.1 (95% CI, 3.5-6.8; P = .03). Two participants achieved complete disease resolution by the study conclusion. Dermatology Life Quality Index scores pretreatment and posttreatment scores did not differ (4.3; 95% CI, 1.3-7.4 vs 2.3; 95% CI, 1.3-3.4; P = .09). There was no change in cytokine concentrations.

Figure. Pretreatment and Posttreatment of Grover Disease With Blue Light Phototherapy.

Images of a patient with Grover disease before (A) and after (B) receiving 15 treatments of blue light phototherapy.

No treatment-related adverse events occurred. Five participants preferred blue light therapy to topical therapies, 3 had no preference, and 2 preferred topical therapies. All patients indicated comfort using blue light devices at home.

Discussion

There are few well-designed studies evaluating the efficacy of Grover disease treatments. In this study, blue light was associated with decreased lesion count and improved itch without adverse events. A limitation is that spontaneous remission was not controlled for in this study; however, plausible mechanisms may support the use of blue light. Similar to NBUVB, blue light may elicit an antipruritic effect mediated by skin sensory nerves.³ Furthermore, blue light may induce regulatory T cells, causing apoptosis of T cells.⁴ Though not powered to detect a difference, serum cytokine concentration did not change from baseline to conclusion, possibly suggesting a localized rather than systemic effect.

Although prior small case series have illustrated a potential benefit of NBUVB for Grover disease, NBUVB is increasingly expensive, and incurs greater risk of sunburn and ocular damage.⁵ Treatment with UV-B light requires inefficient, expensive fluorescent bulbs, compared with blue light, which is made by low-cost light-emitting diodes that generate less heat with greater efficiency than conventional fluorescent systems.⁶ As a nonionizing energy source, blue light phototherapy may be a safer, cost-effective therapeutic modality conducive to home use. Future randomized controlled trials enrolling patients of all skin types are warranted to explore blue light therapy efficacy for treatment-resistant Grover disease.

Supplement.

eMethods.