Excimer Laser Therapy for Pigmented Purpuric Dermatosis: A Case Study

Introduction

PPD is a rare disease with poorly understood epidemiology [1,2]. It results from inflammation of the capillaries causing venous hypertension and extravasation of erythrocytes into the soft tissue, causing the classic purpura-like lesions seen on physical examination [1]. PPD most commonly presents on the lower legs, although can also affect the arms and torso [1]. While the exact etiology of PPD is poorly understood, it is most often described as idiopathic in nature [1]. PPD commonly presents with concomitant disease, such as venous stasis, and multifactorial etiology should be considered for characteristic lesions [1]. Other potential causes of PPD include medications, such as acetaminophen and aspirin, abnormal humoral immunity, and excessive exercise [1]. The diagnosis of PPD is primarily clinical; however, biopsy should be considered with persistent or worsening lesions to assure against more sinister look-alikes such as mycosis fungoides or Kaposi sarcoma [1]. Histopathology of PPD classically shows perivascular lymphohistiocytic inflammation around capillaries, erythrocytes extravasated in the dermis, and mild spongiosis with lymphocyte exocytosis in the epidermis [1].

While PPD is benign in nature, it can be bothersome to patients because of pruritus, weeping, and poor cosmetic results, and treatment is often very challenging [1]. There are no treatment guidelines for PPD, and it is often chronic in nature, with a relapsing course when treatment is discontinued [2]. The first step of treatment is to determine if there is a specific cause of the PPD or if it is idiopathic in nature [1]. If a medication reaction is suspected, the medication should be stopped, and the rash should clear after discontinuation [1]. Compression stockings can also be helpful if concomitant venous stasis is suspected [1]. However, if no known cause is found, options for treatment increase without necessarily increasing in efficacy.

One new focus for treatment of PPD includes phototherapy. Several different phototherapies have been reported as successful in PPD treatment [3–7]. While the exact mechanism varies based on the type of laser used, the underlying mechanism of phototherapy works to modify the body’s inflammatory response [4]. Case reports have been published regarding psoralen plus ultraviolet (UV) A laser, narrow band UVB, advanced fluorescence technology pulsed light, and fractional non-ablative 1540 nm erbium: glass laser in the treatment of PPD [3–7]. However, these options have varying efficacy and likelihood for recurrence [3–7].

One laser that has specifically shown promise is the narrow band UVB laser [3]. Previous case reports have shown it to be effective in inducing remission with laser treatment 3 times a week for 3 weeks and 1 time a week for 3 weeks [3]. Another narrow band UVB treatment regimen includes 3 times a week for 7 weeks and 2 times a week for 15 weeks [4]. The mechanism underlying treatment with UVB laser is thought to work by decreasing the inflammatory reaction and altering cytotoxic immunity, allowing for resolution of the lesion [3,4,9]. However, due to the sparse publications of the successful use of this type of laser to treat PPD, more research is needed to categorize treatment regimens and timelines.

Phototherapy is a new, developing treatment option for PPD; however, there is little published literature regarding how to successfully induce remission with this treatment option. The present case focuses on the use of excimer laser therapy, a 308 nm pulsed gas laser, to successfully induce and maintain remission in a patient with PPD.

Case Report

A 77-year-old man with a past medical history of hypertension and hyperlipidemia presented to our outpatient dermatology clinic with concerns of a bilateral lower extremity rash present for 1 year. He reported that symptoms initially began after a 1-week long hospitalization for treatment of COVID-19. Upon discharge from the hospital, he reported new-onset swelling and a pruritic erythematous rash of his bilateral lower extremities. The patient reported he had been wearing compression stockings daily since discharge, without recovery, and that his hemoglobin level had been elevated since he was diagnosed with COVID-19. Prior to presentation at this dermatology office, he saw an allergist and a vascular specialist for further evaluation. However, both of these evaluations were without significant findings. He endorsed 5 intermittent exacerbations within the last year, associated with intense pruritus and weeping of his legs. Physical examination revealed reddish-brown macules and coalescing patches with studded petechiae on the bilateral distal anterior tibias with concomitant venous stasis changes (Figure 1A, 1B). The differential diagnosis at this time consisted of allergic or irritant contact dermatitis, vascular insufficiency, leukocytoclastic vasculitis, and PPD. Owing to the longevity of the lesions and the patient’s desire for a definitive diagnosis, a 3-mm punch biopsy was conducted on his anterior medial thigh. In the interim, the patient was advised to continue wearing compression stockings daily and to start desonide 0.05% cream twice daily for 2 weeks, then take a 1-week break and repeat the course as necessary. Biopsy results were available 1 to 2 weeks later and were significant for perivascular lymphocytes and histiocytes in the superficial dermis, with extravasation of erythrocytes, which was negative for PAS and Perls iron staining, confirming the diagnosis of PPD, and most consistent with Schamberg disease subtype (Figure 2). Medication review after diagnosis was negative for medications with a known association with PPD [1]. After review of the patient’s presentation and history, his presentation was thought to be idiopathic due to the lack of an identifiable underlying cause.

During the 2-week continuous treatment with desonide cream, the patient confirmed remission of the lesions; however, during his break, it would flare and again become symptomatic. At one time, there was an open lesion on the anterior lower leg that was erythematous and tender. A culture of the lesion grew Staphylococcus aureus, and he was treated with doxycycline 100 mg twice a day for 4 weeks. These episodic exacerbations were extremely bothersome to the patient and affected his quality of life. After discussion of the limited treatment options for PPD, the patient opted for phototherapy. He started on excimer laser treatment twice per week at 300 mJ/cm2. The dose was increased to 1600 mJ/cm2 over 2 to 3 weeks, and stabilized at approximately 1300–1600 mJ/cm2 twice a week for his first 2 months of treatment. He showed excellent response to this treatment modality and tolerated it well without excessive erythema, tenderness, or burning. Three months after initial treatment, he was titrated down to once-weekly treatments at the same approximate level, and maintained his remission status. Finally, after 2 additional treatment months, he was switched to once every other week at the same level of 1300–1600 mJ/cm2. He has been in complete remission since starting treatment, without instances of open sores or weeping or adverse effects from the excimer laser treatment (Figure 3).

Discussion

This case report discusses a new, effective treatment option for PPD with phototherapy. Treatment of PPD is challenging and, owing to the lack of guidelines, is often based on provider preference and case report documentation of successful treatment [2]. Potential treatments include topical corticosteroids, supplements, such as bioflavonoid and rutoside, systemic immunomodulators, such as colchicine or cyclosporine, and laser treatment or phototherapy [1,2]. For patients with pruritus, topical steroids and calcineurin inhibitors are often used to decrease bothersome symptoms, but do not clear the visible lesions [2]. Oral agents, such as rutoside, pentoxifylline, flavonoids, calcium dobesilate, and cyclosporine, have also been reported to successfully treat PPD, but dosage and duration of therapy are not agreed upon, and there is risk for systemic reaction or immunosuppression [2]. Our patient attempted to treat PPD with desonide, compression stockings, and diuretic therapy before pursuing phototherapy; however, he was unable to maintain remission of his symptoms.

Laser treatments and phototherapy have been described in the literature as successful treatment mechanisms in a small number of case reports for PPD [3–7]. Examples of documented treatment options for PPD include 1540-nm erbium laser monthly for 4 treatments, narrow band UVB treatment 3 times weekly until clearance, twice weekly for 3 weeks, and once weekly for 1 week, and narrow band UVB 3 times a week for 20 sessions and bi-weekly for 30 sessions [2–4]. However, there are other lasers and treatment regimens documented in the literature [1,5–8]. In the present case, we used an excimer laser, with complete resolution of symptoms. Excimer laser is a 308-nm high-pressure pulse gas laser that implements UV light and has not previously been described in the treatment of PPD [8]. While other narrow band UVB phototherapies have been documented as successful, this specific laser has a dearth of literature describing its use in PPD. It has also been used to successfully treat a variety of other conditions varying from psoriasis and vitiligo to refractive errors of the eye [8]. While the exact mechanism of action in PPD is not known, it is thought to decrease the inflammatory reaction and alter cytotoxic immunity, allowing for resolution of the lesion [9]. While there are some potential adverse effects, including erythema, blistering, and increased photoaging, overall, photo-therapy is a localized, safe, non-invasive treatment option that can provide optimal results for PPD [9]. More research is needed to explore excimer laser therapy as an effective treatment method of PPD. Future studies could explore a standardized treatment regimen for PPD via excimer laser.

Conclusions

PPD is a poorly understood rare disease that is challenging to treat. Laser and phototherapy have shown some promise in the literature to help resolve stubborn PPD lesions without recurrence; however, excimer laser therapy has not been previously described [3–8]. Our report highlights a persistent case of PPD that resolved completely after treatment with excimer laser. More research is needed to better describe the treatment of PPD with excimer laser.