Pinpoint papular variant of polymorphous light eruption: clinical and pathological correlation

Demographics and clinical presentations of 844 patients with light and dark skin types with polymorphous light eruption and chronic actinic dermatitis evaluated over 23 years

INTRODUCTION

Polymorphous light eruption (PMLE) and chronic actinic dermatitis (CAD) have been classically described in White individuals, although recent studies have reported higher prevalence in patients with dark skin types, particularly African Americans.

OBJECTIVE

To evaluate for differences in demographic, and clinical features between persons with light and dark skin types who have PMLE and CAD.

METHODS

Retrospective review of patients with PMLE and CAD who were diagnosed from January 1, 1998, through November 31, 2021, at a single academic dermatology center.

RESULTS/DISCUSSION

A total of 844 patients (725 [85.9%] female; mean [SD] age of onset: 41.7 [16.9] years) were diagnosed with PMLE, and 60 patients (22 [36.6%] female; mean age, [SD]: 60.6 [10.6] years) of age at presentation, disease duration of 8.2 [7.3] years were diagnosed with CAD. Although just over 50% of the general clinic population was White, the prevalence of PMLE and CAD was significantly higher in dark-skinned individuals compared to light-skinned individuals (PMLE: 625 [74.0%] vs. 219 [25.9%], p value < .001; CAD: 43 [71.6%] vs. 17 [28.3%], p value = .003) respectively. The pinpoint papular variant of PMLE (PP-PMLE) was predominantly seen in dark-skinned individuals.

CONCLUSION

A substantial proportion of PMLE and CAD cases are present in dark-skinned individuals. PP-PMLE can be mistaken for lichen nitidus. As such, recognition of this entity is important for adequate evaluation and management of patients with PMLE.

Immunopathogenesis and management of polymorphic light eruption

Polymorphic light eruption (PLE) is the most common immunologically mediated photodermatosis, demonstrating many abnormalities caused by critical failure of ultraviolet (UV)-induced immunosuppression. The unique expression of antimicrobial peptides in PLE, which is most likely determined by alteration of microbiome components upon UV exposure, implicates their possible triggering role and pathogenic significance in the eruption. The review aims to clarify current knowledge regarding the immunological disturbances correlated with PLE that serve a base for better understanding of molecular pathogenesis of the disease and the development of new therapeutic strategies. Preventive treatment with broad-spectrum suncreens and sunscreens containing DNA repair enzymes, as well as natural photohardening with graduate exposure to sunlight in early spring could be sufficient in milder cases. Antioxidants and topical calcipotriol are promising approach for adjuvant prevention. Phototherapy, mainly with narrow band UVB rays, is more appropriate method in severe cases of the disease. The established treatment options for PLE include local and systemic glucocorticoids, systemic nonsedative antihistamines for itch relief, and rarely, immunosuppressive drugs in the refractory cases. Like medical photohardening, afamelanotide has the potential of photoprotection by inducing a melanization of the skin. Afamelanotide is believed to be a possible new treatment option for very severe and refractory cases of PLE. Targeting the main pruritogenic cytokine, IL-31, opens a new road for the development of novel therapeutic approaches to combat moderate and severe itching in cases of PLE with intense pruritus.

Polymorphous Light Eruption- An Indian Scenario

Polymorphous light eruption (PMLE) is the most common, idiopathic, acquired photodermatosis, characterized by abnormal, recurrent, and delayed reaction to sunlight. Polymorphous light eruption is common worldwide but the morphology, distribution, and pigmentary changes are unique in Indian skin which is discussed in this review. The prevalence of PMLE is around 10–20% in the general population. It commonly occurs in females between 20and 30 years of age. It is the most common photodermatosis in school-going children. Visible light sensitivity is an important phenomenon in PMLE. It typically presents as recurrent and chronic lesions over photoexposed sites. Initially, patchy erythema occurs with pruritus. Most of the Indians belong to type IV to type VI skin and pigmentary changes are commonly seen. The unique feature of PMLE in Indian skin is the pigmentary change which varies from hypopigmented to hyperpigmented lesions. These pigmentary changes may occur alone or in combination with erythematous or skin-colored lesions. The pigmentary lesions are seen in more than 50% of lesions. The histopathology of PMLE is characterized by the presence of hyperkeratosis, spongiosis with or without the presence of liquefactive degeneration in the epidermis. Dermal changes in the upper and mid dermis include the presence of dense perivascular lymphocytic infiltrate. The management of PMLE includes both preventive measures and medical management. Topical sunscreens, topical steroids, hydroxychloroquine and antioxidants play a very important role.

Polymorphous Light Eruption

Polymorphous light eruption (PLE) is the commonest immuno-mediated photodermatosis. It occurs after solar or artificial UV-light exposure and affects only the sun-exposed areas with preference of the V-area of the chest, of arms and forearms, legs, upper part of the back, and rarely the face. The lesions are itching or burning, and vary morphologically from erythema to papules, vesico-papules and occasionally blisters, plaques, sometimes erythema multiforme-like, insect bite-like wheals and purpura. The clinical manifestations befall within a few hours to days from light exposure, last a few days, and subside in about a week without sequelae. Its diagnosis is based on history, morphology and phototests. PLE is considered as a delayed hypersensitivity response to newly UV induced, but still unidentified, antigen(s). Usually, MED is normal, but the provocative phototests with UVA or UVB reproduce the spontaneous lesions in about 50% of the patients. Broad spectrum sunscreens and antioxidants, photohardening with PUVA or narrow band UVB may be beneficial to prevent the disease. Therapy is based mainly on topical or systemic corticosteroids.

Lichen planus and other lichenoid dermatoses: Kids are not just little people

Lichenoid dermatoses, a group of inflammatory skin conditions with characteristic clinical and histopathologic findings, range from common to rare. Classic lichen planus typically presents as pruritic, polygonal, violaceous flat-topped papules and plaques; many variants in morphology and location also exist. Other lichenoid dermatoses share similar clinical presentations and histopathologic findings. These include lichenoid drug eruption, lichen planus-like keratosis, lichen striatus, lichen nitidus, and keratosis lichenoides chronica. Epidemiologic characteristics vary among each lichenoid disorder. While classic lichen planus is considered a disease of adults, other lichenoid dermatoses may be more common in younger populations. The literature contains an array of reports on the variations in presentation and successful management of lichen planus and lichenoid dermatoses among diverse populations. Familiarity with the characteristics of each lichenoid dermatosis, rare or common within each patient population, is key to accomplishing timely recognition and effective management.

A clinical study of the spectrum of photodermatoses in dark-skinned populations

BACKGROUND

Photodermatoses are characterized by an abnormal cutaneous response to 'ordinary' light exposure.

AIM

To study the spectrum of photodermatoses in populations with dark skin (skin types IV-VI) at a tertiary referral centre.

METHODS

Consecutive patients with skin lesions confined to or predominantly located on photoexposed parts of the body and/or with photosensitivity were enrolled in the study, and their clinical details were recorded. Diagnosis was made on clinical grounds, and relevant investigations were carried out if required. Patch and photopatch testing were carried out in patients with chronic actinic dermatitis (CAD). Selected patients with CAD also underwent phototesting with UV (ultraviolet) A and broadband UVB light.

RESULTS

We enrolled 362 patients (146 men, 216 women; mean age 35.6 ± 13.6 years), with mean disease duration of 3.4 years. The Fitzpatrick skin types were IV and V (52.8% and 47.2% of patients, respectively). Polymorphic light eruption (PMLE) was the commonest photodermatosis seen, affecting 59.7% of patients, followed by CAD (13.8%), collagen vascular disorders (7.7%), photoaggravated atopic dermatitis (6.1%), actinic lichen planus (ALP; 2.2%) and lichen planus pigmentosus (LPP; 1.6%). The majority (84.5%) of patients were involved in indoor work. Papular PMLE (37%) was the most common variant of PMLE, followed by pinpoint (31%), eczematous (22.2%), lichenoid (5.5%) and plaque-type (4.1%) PMLE.

CONCLUSIONS

The spectrum of photodermatoses in Indian patients with dark skin phototypes (IV and V), is similar to that reported from other parts of the world. PMLE was the commonest photodermatosis seen, with the pinpoint and lichenoid variants accounting for over one-third of the PMLE cases. ALP and LPP were also not uncommon in our dark-skinned population.

Photodermatoses in pigmented skin

Photodermatoses are a group of skin diseases primarily caused by, or exacerbated by exposure to ultraviolet and or visible radiation. The effect of sunlight on skin depends on a number of factors including skin colour, skin phototype and the content and type of melanin in the skin. There are only a few studies describing photodermatoses in populations with dark skin. A PubMed search was conducted to summarize currently available information on differences in biology of melanin in dark and light skin and photodermatoses in dark skin. Dark skin is characterised by higher content of melanin, higher eumelanin to pheomelanin ratio, lower tyrosinase activity, and more effective distribution of melanin for protection against ultraviolet light. Photodermatoses are common in dark skinned patients with some variation in the spectrum of photodermatoses. Polymorphous light eruption (PMLE) is the commonest, followed by chronic actinic dermatitis. Pin-point papular and lichenoid variants of PMLE and actinic lichen planus are more frequent in dark skin whereas actinic prurigo, solar urticaria and hydroa vacciniforme are uncommon. Photodermatoses are common in dark skinned patients despite better natural photoprotection. It is proposed that lichenoid photodermatoses may be added to the classification of photodermatoses in dark skin.

Clinicopathologic study of solar dermatitis, a pinpoint papular variant of polymorphous light eruption in Taiwan, and review of the literature

BACKGROUND/PURPOSE

A mild, micropapular eruption previously coined as "solar dermatitis" on the extensor of the forearm is a common form of photodermatitis in Taiwan. This study aimed to investigate the clinicopathologic findings of "solar dermatitis", the micropapular type of photodermatitis.

METHODS

We characterized the features of this photodermatitis by retrospectively reviewing and analyzing all such cases in a medical center in Southern Taiwan diagnosed during October 1988 to November 2010.

RESULTS

A total of 34 Taiwanese patients, all with Fitzpatrick skin type III-IV, were included (M:F = 1:1; mean age = 33.5 years; range = 9-62 years). Patients typically presented numerous, monomorphous, pinhead-sized micropapules on the extensor of the forearm after a recent, more intense sun exposure. The rash was often mildly pruritic and recurred in the summer, but usually resolved in a few days after sun protection and topical corticosteroid treatment. Reduced minimal erythema dose to UVB was noted in 2 of the 5 patients tested. Histopathologic examination (n = 10) revealed a mild spongiotic dermatitis.

CONCLUSION

The clinicopathologic findings of the "solar dermatitis" closely resembled those of the pinpoint papular variant of polymorphous light eruption (PP-PMLE) affecting African Americans and Asians in Singapore. PP-PMLE, micropapular light eruption in Japanese, summertime actinic lichenoid eruption in Indians and the present photodermatitis might represent a common, micropapular variant of PMLE affecting darker skin populations.