Dapsone for Treatment of a Neutrophilic Predominant Variant of Polymorphous Light Eruption: A Case Report

Abstract

Introduction

Polymorphous light eruption (PMLE) is a self-limiting immunologically mediated photodermatitis that results in the eruption of pruritic lesions hours to days after sun exposure.

Case Presentation

The case presented here highlights the clinical presentation of a 39-year-old Caucasian male with an itchy, blistering rash affecting the chest, abdomen, arms, and legs. History and examination findings were suggestive of a neutrophil predominant variant of PMLE. The rash was evaluated through laboratory testing, potassium hydroxide (KOH) microscopy, wound culture, and punch biopsy. The hematoxylin and eosin (H&E) stain results from the biopsy demonstrated eosinophilic and neutrophilic spongiosis. Various therapeutic modalities were explored in the treatment of this patient including topical steroids, oral steroids, oral antifungals, and oral antihistamines with a lack of remission of the symptoms. Due to the persistent nature of the rash and neutrophil predominance visualized on H&E, dapsone was begun with eventual cessation of symptoms and resolution of the rash.

Conclusion

This case highlights the importance of scrutinizing the underlying pathophysiology of a patient’s symptoms despite variations in the suspected clinical picture for effective management of symptoms.

Introduction

Polymorphous light eruption (PMLE) is an immunologically mediated photodermatitis [1]. Moreover, it is a type four hypersensitivity reaction that occurs in the skin after exposure to ultraviolet (UV) light. The delayed nature of a type four hypersensitivity reaction leads to the occurrence of pruritic papules and plaques hours to days after UV exposure in the setting of PMLE [2]. As the name suggests, the morphology of these lesions is variable. Patients may experience erythema, papules, vesicopapules, plaques, blisters, wheals, or purpura [3]. In most cases, these lesions can be expected to resolve in days to weeks after onset [4]. The exact pathogenesis is unknown but current theories suggest that there is an unknown photoantigen that elicits an immune response upon exposure to UV light. In patients affected by PMLE, T-cell function remains active and is unsuppressed until after photohardening is complete, whereas in unaffected individuals, UV-induced suppression occurs upon exposure to the unknown photoantigen [5]. As melanin serves as a protective factor against UV exposure and damage, lighter skin tones are more susceptible to PMLE than darker skin tones due to the pathogenesis of the disease. Additionally, the prevalence of PMLE is much higher in females than in males with typical onset occurring in the second through fourth decades of life [5]. Suggested management of this disease is prophylaxis for patients with a history of severe reactions, or treatment after onset for patients with mild or moderate reactions. Prophylaxis can be achieved through a seven- to ten-day course of oral corticosteroids [4]. As PMLE is a self-limiting disease, first-line treatment focuses on sun avoidance or sun protection with sunscreen or protective fabrics. For mild cases of disease, concurrent topical steroids and oral antihistamines are suggested. For moderate cases, a short course of oral steroids in addition to the aforementioned is appropriate. For severe cases, phototherapy, immunomodulators, and anti-inflammatory agents may be appropriate [6]. The case described here focuses on a patient with a presentation of PMLE with atypical workup findings, unable to achieve remission with commonly used first- and second-line treatments.

Case Report

The subject patient is a 39-year-old Caucasian male who first presented to the dermatology clinic for complaints of rash in January 2025. The rash affected his chest, abdomen, arms, and legs. He was experiencing associated symptoms such as itching, bleeding, mild blistering, scale, and pain. Prior to the onset of the rash, the patient had identified recent stressors such as house construction in late December 2024, the use of new laundry detergent, and the application of coconut oil to the skin. The patient lives in an environment with variable weather patterns and moderate sun exposure in the winter months. He admitted to occasional sun exposure but did not recall excessive exposure such as recent sun burns. To help address the itchiness, the patient had tried Sarna anti-itch lotion, Neosporin anti-itch, and over-the-counter cortisone ointment. These partially alleviated the itchiness. Physical examination at the time of visit demonstrated geometric, erythematous, scaly, well-demarcated papules and plaques over the bilateral forearms, abdomen, chest, and legs. Clinical images are unavailable from this encounter. At this time, the patient opted for conservative management and was started on a regimen of prednisone 60 mg daily with a taper of 10 mg every three days in addition to topical triamcinolone 0.1% ointment twice daily. Both the patient and medical care team in a shared decision-making process, selected to monitor the rash’s evolution with the new management plan prior to proceeding with a biopsy at a later date if needed. The patient was advised to follow up in clinic if symptoms persisted or worsened despite adherence to treatment recommendations.

In March 2025, the patient returned to the dermatology clinic. He noted that his symptoms improved with prednisone and triamcinolone. However, in late February, the patient went on a vacation and experienced excessive sun exposure leading to reoccurrence of the rash. The patient did not capture photographs of the rash at this time. Symptoms at this time were itching, blistering, pain, and bleeding upon excoriation. Both itchiness and pain were rated to be 4/10 at this time. Physical examination demonstrated rash over the neck, upper chest, arms, and legs in a more markedly photo-distributed pattern (Fig. 1). Workup with potassium hydroxide (KOH) microscopy and punch biopsy was completed. The KOH microscopy sample was taken from the left superior upper arm and demonstrated budding yeast, with the absence of hyphae. The punch biopsy sample was collected from the left superior upper arm for both hematoxylin and eosin and direct immunofluorescence stains. The hematoxylin and eosin demonstrated eosinophilic and neutrophilic spongiosis (Fig. 2). Papillary edema was not impressive (Fig. 3). Direct immunofluorescence showed C3 scattered grains along the basement membrane. At this time, the patient was started on an updated regimen of fluconazole 150 mg once weekly for four weeks, prednisone 60 mg with a taper of 10 mg every three days, and triamcinolone 0.1% ointment twice daily.

Fig. 1.

Clinical images of the patient’s disease presentation during the March clinical visit. a Erythematous scaly papules and pustules over the bilateral dorsal arms with a circumferential distribution of erythematous eczematous rash around the inferior anterior neck and superior chest. b The left superior arm, the site of punch biopsy for collection of the DIF and H&E. c Eczematous papules superimposed on a background of erythema on the bilateral shins in a markedly photo-distributed pattern. d Excoriated eczematous papules and plaques superimposed on a background of erythema over the right lower leg.

Fig. 2.

H&E stain under 200× magnification. a Parakeratosis overlying an epidermis with erosion, acanthosis, and spongiosis. b Neutrophilic pustules within the epidermis with many eosinophils consistent with neutrophilic and eosinophilic spongiosis.

Fig. 3.

H&E stain under 40× magnification. Superficial perivascular lymphocytic infiltrate with many eosinophils and scattered neutrophils in the dermis are present. Papillary dermal edema was not impressive.

In April 2025, the patient returned due to a recurrence of the rash and symptoms on the neck, chest, and arms after completion of the prednisone taper. Workup was continued at this time with wound culture and laboratory testing. Wound culture results showed the presence of coagulase-negative Staphylococcus species and Staphylococcus aureus. Laboratory testing consisted of a complete blood count with differential, comprehensive metabolic panel, autoimmune disease lab markers, and serum protein electrophoresis (Tables 1–3). Comprehensive metabolic panel results were overall unremarkable with some labs slightly buffering outside of the reference range (Table 1). More notably, complete blood count results showed decreased neutrophil percentages and increased lymphocyte percentages (Table 2). The autoimmune disease lab markers and serum protein electrophoresis were unremarkable. At this time, a treatment regimen with dapsone 50 mg daily for 60 days, Zyrtec 30 mg twice daily, and triamcinolone 0.1% ointment was recommended.

Table 1.

Abnormal CBC and CMP Results

Lab	Value	Reference range
CMP results
Chloride	111 ↑	102–110 mmol/L
Carbon dioxide	19 ↓	20–26 mmol/L
Creatinine	0.71 ↓	0.72–1.25 mg/dL
ALT	64 ↑	0–55 U/L
CBC results
MCH	33.9 ↑	25.8–33.1 pg
MCHC	36.2 ↑	31.9–35.2 g/dL
Neutrophil %	31.3 ↓	39.4–72.5%
Lymphocyte %	53.3 ↑	17.6–49.6%
Neutrophil # (ANC)	1.47 ↓	2.00–7.40 k/μL

The CMP and CBC panel with results outside of the indicated reference range. Unreported labs held values within the appropriate reference ranges. CMP, comprehensive metabolic panel; CBC, complete blood count.

Table 3.

Protein Electrophoresis Results

Lab	Value	Reference range
Albumin	4.52	3.71–5.01 g/dL
Alpha 1 Globulin	0.25	0.19–0.46 g/dL
Alpha 2 Globulin	0.63	0.48–1.05 g/dL
Beta Globulin	0.79	0.48–1.10 g/dL
Gamma	0.70	0.62–1.51 g/dL

The laboratory results for the protein electrophoresis. This test evaluated the presence of small M proteins which may be seen in diseases such as amyloidosis, myeloma, macroglobulinemia, and plasmacytomas.

Table 2.

Autoimmune Panel Results

Lab	Value	Reference range
ANA IgG by ELISA	None detected	N/A
dsDNA Ab IgG IFA	<1:10	<1:10
Immunoglobulin E	172	≤214 kU/L
Rheumatoid factor	10	0–14 IU/mL
Smith (ENA) Ab; IgG	1	0–40 AU/mL
Smith/RNP (ENA) Ab, IgG	6	0–19 units
SSA 52 Ab, IgG	3	0–40 AU/mL
SSA 60 Ab, IgG	0	0–40 AU/mL
SSB (La) (ENA) Ab, IgG	6	0–40 AU/mL
CCP Ab, IgG/A	3	0–19 units

The results of autoimmune laboratory markers assessed to rule out several etiologies such as connective tissue disease, systemic lupus erythematosus, Sjögren’s syndrome, systemic sclerosis, and rheumatoid arthritis. All values were within the indicated reference ranges.

One week later, the patient returned for follow-up and noted significant improvement of his symptoms now rating itchiness 1/10 and pain 0/10. At this follow-up visit, triamcinolone 0.1% ointment was discontinued and tacrolimus 0.1% ointment as needed was started. The patient returned in June 2025 for a follow-up visit and stated complete resolution of his symptoms with confirmation upon physical examination. As the patient was no longer actively inflamed from the rash, referral for phototesting and patch testing was offered for further evaluation, but the patient deferred at this time.

Discussion

Although several differential diagnoses were considered, the authors believe PMLE to be the most likely in this patient. The patient had reported that this was the first time experiencing a reoccurring rash of this nature. The patient’s age of 39 years fits the clinical picture of the expected onset of PMLE. Additionally, the morphology and pruritus experienced by this patient is characteristic of PMLE. Although there was no definitive identified trigger upon the first occurrence of rash in January, the recurrence of the rash upon sun exposure such as with a vacation as seen in this patient during the March clinical visit also fits the clinical picture of PMLE.

Evaluation for PMLE is completed through a skin biopsy. The subject patient’s histopathological findings demonstrated the presence of eosinophilic and neutrophilic spongiosis. These findings may be seen in PMLE, especially the presence of neutrophils in early lesions [5]. However, the literature supports that the definitive diagnostic grade for the histopathology of PMLE is the presence of prominent papillary dermal edema and dense perivascular lymphocytic infiltrate [7]. An extensive review of the literature revealed a case in which the histopathology demonstrated an unusual presence of neutrophilic infiltrate. Thus, reports of a neutrophilic predominant variant of PMLE are rare and further research is indicated [8]. Photoallergy is another photodermatitis with a similar clinical presentation to PMLE. The histopathological findings seen in photoallergy are epidermal spongiosis, acanthosis, superficial perivascular infiltrate with lymphocytes and eosinophils [7]. These findings are more consistent with what was seen in the subject patient. However, photoallergy is caused by the interaction of UV light with an applied substance on the skin which then produces an allergic reaction. No identifiable substances were persistently applied by this patient as he had stopped the use of coconut oil and fragranced laundry detergent prior to the January clinical visit. Sweet syndrome is an acute febrile neutrophilic dermatosis. This clinical picture is an eruption of painful, erythematous nodules and plaques often in the setting of fever although not always. Other associated findings are arthralgia and systemic symptoms. The histopathological findings for Sweet syndrome are diffuse dense neutrophilic infiltrate in the reticular dermis with interstitial leukocytoclastic nuclear debris and papillary edema [9]. The subject patient’s histopathology showed the presence of neutrophils in the epidermis rather than in the reticular dermis; this in conjunction with the lack of systemic symptoms made this differential diagnosis less likely.

Treatment of PMLE is dependent on clinical severity (Table 4). In the past, clinical severity had been determined by the PMLE-severity assessment score. However, a study that compared the PMLE-severity assessment score to the results from phototesting in a group of patients found that the score did not reliably predict severity of disease [10]. Severity of disease can be determined based on the clinical presentation and at the discretion of the provider. Mild disease courses focus on sun avoidance or protection with sunscreen or protective fabrics. The concurrent use of topical steroids and oral antihistamines is appropriate for this disease presentation. For moderate disease courses, a short course of oral steroids in addition to the aforementioned may be utilized. For severe cases, phototherapy, immunomodulators, and anti-inflammatory agents may be appropriate [6]. Commonly used systemic agents include cyclosporine, hydroxychloroquine, and azathioprine [6].

Table 4.

PMLE Treatment Options

Severity	Treatment
Mild	Sun avoidance
	Sun protection
	Topical steroids
	Oral antihistamines
Moderate	Oral steroids
Severe	Phototherapy
	Anti-inflammatory agents
	Immunomodulators

An example of therapeutic treatment options for PMLE based on the severity of disease presentation.

Due to the strong neutrophilic component seen in this patient’s histopathology, dapsone was selected as the drug of choice after failure of topical steroids and oral steroids. Dapsone is a medication with both antibacterial and anti-inflammatory mechanisms of action. Dapsone was selected in this case due to the anti-inflammatory properties. Its anti-inflammatory properties are caused by the modulation of neutrophilic activity. This action makes dapsone effective for the off-label use of many dermatological conditions especially those with elevated neutrophils or eosinophils such as in Sweet syndrome and pyoderma gangrenosum [11].

Conclusion

Here, a case of a 39-year-old Caucasian male with a clinical history suggestive of PMLE and histopathology suggestive of a neutrophilic variant of PMLE has been presented. This patient’s condition temporarily improved with oral steroids with recurrence of his symptoms after discontinuation of the medication. Successful management was achieved with the use of 50 mg of dapsone over 60 days. This case highlights the importance of scrutinizing the underlying pathophysiology of a patient’s symptoms despite variations in the suspected clinical picture for effective management of symptoms.

Statement of Ethics

Ethical approval was not received for this human study because this manuscript is a single-case report. For a case report to be considered “research” and require IRB approval, it typically involves more than two or three patients and aims to contribute to generalizable knowledge. All adult participants provided written informed consent to participate in this study. Written informed consent was obtained from the individuals for publication of the details of their medical case and any accompanying images. The written informed consent form is held at the institution at which the research was conducted. This retrospective review of patient data did not require ethical approval in accordance with local/national guidelines. The CARE Checklist has been completed by the authors for this case report and is attached as online supplementary material (for all online suppl. material, see https://doi.org/10.1159/000552174).

Conflict of Interest Statement

Dr. Hopkins is supported by a career development award from the Dermatology Foundation and has received consulting fees from Priovant Therapeutics.

Funding Sources

The University of Utah via the Karger Publishers Transformative Agreements covered the cost of manuscript publication.

Author Contributions

Oluwafunke Oluwatosin Ogunremi: conceptualization, investigation, funding acquisition, and writing – original draft, review, and editing. Zachary Hopkins: conceptualization, investigation, project administration, supervision, and writing – review and editing.

Funding Statement

The University of Utah via the Karger Publishers Transformative Agreements covered the cost of manuscript publication.

Data Availability Statement

The data that support the findings of this study are openly available in PubMed at https://doi.org/10.1007/s40257-024-00879-8. Further inquiries can be directed to the corresponding author.