92: Polymorphic Light Eruption Flashcards
What is the most common photodermatosis that typically presents in the spring?
Polymorphic light eruption (PMLE) is the most common photodermatosis, particularly among young women in temperate climates.
What are the clinical features of PMLE?
PMLE presents as a pruritic, erythematous eruption of variable inter-individual morphology, usually papular, on sun-exposed skin areas, occurring within hours to days of exposure, with full resolution in several days.
What is the treatment of choice for photohardening in PMLE?
The treatment of choice for photohardening in PMLE is broad-spectrum sunscreen use, oral or topical steroids, and prophylactic low-dose immunosuppressive phototherapy.
What is the relationship between UV exposure and PMLE lesions?
PMLE lesions occur after ultraviolet (UV) exposure, typically within hours to days, and usually resolve fully without scarring after UV exposure ceases.
Which sites are usually spared in PMLE?
The face and earlobes are usually spared in PMLE.
What is the incidence of PMLE in the UK and Australia?
The incidence of PMLE is approximately 15% in the UK and 5% in Australia.
What is the role of prednisone in the treatment of PMLE?
Prednisone is taken initially at the first sign of pruritus in PMLE.
What is the significance of a positive family history in PMLE patients?
A positive family history is present in approximately 18% of PMLE patients, indicating a potential genetic predisposition.
What variant of PMLE has been linked to individuals with darker skin types?
The pinpoint papular variant of PMLE has been linked to individuals with darker skin types, particularly in the African American population and dark-skinned individuals in Asia.
A patient presents with pruritic, erythematous papules on sun-exposed areas after their first intense sunlight exposure in spring. What is the most likely diagnosis, and what is the underlying pathogenesis?
The most likely diagnosis is Polymorphic Light Eruption (PMLE). The underlying pathogenesis involves resistance to UV-induced immune suppression, leading to a delayed-type hypersensitivity reaction against UV-induced antigens.
A patient with PMLE reports that their lesions resolve fully within 7-10 days after UV exposure ceases. What does this indicate about the natural course of PMLE?
This indicates that PMLE lesions typically resolve fully without scarring over several days, occasionally taking 7-10 days.
A patient with PMLE has a history of flares during summer holidays. What phenomenon might explain why their symptoms lessen as summer progresses?
The phenomenon is called ‘hardening,’ where repetitive exposures to sunlight lead to skin adaptation, making lesions less likely to occur or less severe.
A patient with PMLE is advised to avoid sun exposure and use broad-spectrum sunscreen. Why is broad-spectrum sunscreen particularly important for PMLE patients?
Broad-spectrum sunscreen is important because it protects against both UVA and UVB radiation, which are implicated in triggering PMLE.
A patient with PMLE is prescribed 20-30 mg of prednisone at the first sign of pruritus. What is the rationale behind this treatment?
Prednisone reduces inflammation and alleviates symptoms, providing relief within several days and preventing recurrences during the same exposure period.
What is the typical clinical presentation of PMLE?
A pruritic, erythematous eruption of variable inter-individual morphology on sun-exposed skin areas.
What is the relationship between PMLE and ultraviolet (UV) exposure?
PMLE occurs after UV exposure, with lesions appearing within hours to days.
Which demographic is most affected by PMLE?
Young women in temperate climates.
What is the incidence of PMLE in the UK?
15%.
What is the significance of Langerhans cells in PMLE?
Increased number of Langerhans cells are found in PMLE lesions.
What is a rare variant of PMLE that occurs on the lower legs?
A rare variant of PMLE is not specified in the text, but it is mentioned that there is one.
What is the typical duration for lesions to resolve after UV exposure in PMLE?
Lesions usually resolve fully within 7 to 10 days after UV exposure ceases.
What is the first sign of an impending PMLE eruption?
Itching may be noted as the first sign of an impending PMLE eruption.
What areas of the body are most affected by PMLE?
Particularly sun-exposed areas that are normally covered during winter, such as the upper chest and the extensor aspects of the arms, are most affected.
What does the term ‘polymorphous’ refer to in the context of PMLE?
The term ‘polymorphous’ describes the variability in lesion morphology observed among different patients with the eruption.
What is the most common form of PMLE?
The papular form, characterized by large or small separate or confluent erythematous and edematous papules that may form clusters, is the most common.
What are the potential variants of PMLE?
Variants of PMLE include papulovesicular, plaque, localized, juvenile spring eruption, solar purpura, benign summer light eruption, and PMLE sine eruption.
What wavebands are most causative in initiating PMLE?
UVA radiation (320 to 400 nm) usually seems more causative than UVB (290 to 320 nm) at initiating PMLE, but lesions can also be induced with UVB alone and sometimes with both waveband ranges.
What systemic symptoms may occur in PMLE patients?
Systemic symptoms in PMLE are rare but may include headache, fever, chills, malaise, and nausea.
What is the relationship between PMLE and lupus?
PMLE lesions may precede the development of lupus, and progression of PMLE to lupus has been proposed, but long-term follow-up studies have not shown a general increased rate of lupus in PMLE patients.
What immunologic aspects are associated with PMLE?
A resistance to UV-induced immune suppression and a subsequent delayed-type hypersensitivity response to UV-modified elements of the skin have been suggested, along with an influx of CD4+ T lymphocytes in early PMLE lesions.
A patient with PMLE is found to have increased numbers of Langerhans cells in their lesions. What does this finding suggest about the immune response in PMLE?
This finding suggests a resistance to UV-induced immune suppression and a subsequent delayed-type hypersensitivity response to UV-modified elements in the skin.
A patient with PMLE reports that their symptoms worsen after using sunscreen. What could explain this paradoxical reaction?
Some sunscreens preferentially block UVB while transmitting UVA and visible light, which can trigger PMLE if exposure times are lengthened.
A patient with PMLE has a history of systemic symptoms like headache and fever after sun exposure. What is the likely cause of these symptoms?
These systemic symptoms may result from UV-induced release of cytokines with pyrogenic activity related to an accompanying sunburn reaction.
A patient with PMLE is found to have a history of photosensitive psoriasis. How might PMLE affect their psoriasis symptoms?
PMLE may exacerbate psoriatic lesions due to resistance to UV-induced immune suppression, which would otherwise counteract psoriatic inflammation.
A patient with PMLE is found to have a localized variant with erythematous-edematous papules on both elbows. What is this variant called?
This localized variant is called juvenile spring eruption.
A patient with PMLE is found to have a rare variant predominantly affecting the lower legs. What is this variant called?
This rare variant is called solar purpura.
A patient with PMLE is found to have a history of lupus erythematosus. How might PMLE and lupus be related?
PMLE lesions may precede the development of lupus, and progression of PMLE to lupus has been proposed in some cases.
What areas are most affected by PMLE during spring?
Particularly sun-exposed areas that are normally covered during winter, such as the upper chest and the extensor aspects of the arms.
What does the term ‘polymorphous’ refer to in PMLE?
It describes the variability in lesion morphology observed among different patients with the eruption.
What is the most common form of PMLE?
The papular form, characterized by large or small separate or confluent erythematous and edematous papules that may form clusters.
What is a potential localized subtype of PMLE that affects boys in spring?
Juvenile spring eruption, characterized by pruritic papules and vesicles on their ear helices.
What type of radiation is usually more causative in initiating PMLE?
UVA radiation (320 to 400 nm) usually seems more causative than UVB (290 to 320 nm).
What effect can sunscreens have on PMLE?
Some patients may note that the use of sunscreens may have a PMLE-enhancing effect if exposure times are lengthened.
What are some systemic symptoms that may occur in PMLE?
Headache, fever, chills, malaise, and nausea may occur, although they are rare.
What is the relationship between PMLE and lupus?
PMLE lesions may precede the development of lupus, but long-term follow-up studies have not shown a general increased rate of lupus in PMLE patients.
What histologic features are associated with early PMLE lesions?
An initial influx of CD4+ T lymphocytes for up to 72 hours, followed by CD8+ T cells in established lesions, consistent with a cellular-mediated immune response.
What is the role of UV radiation in the immune response of healthy skin compared to patients with PMLE?
In healthy skin, UV radiation induces an immunosuppressive Th2 micromilieu, leading to the depletion of epidermal Langerhans cells, neutrophilic infiltration, and the release of immunosuppressive cytokines like IL-4 and IL-10. In contrast, patients with PMLE show resistance to UV-induced immune suppression, favoring an immune response to potential UV-induced antigens and exhibiting a Th1 cytokine profile instead.
How does PMLE affect the induction of contact hypersensitivity?
Patients with PMLE demonstrate a suppression of contact hypersensitivity following UV exposure, indicating impaired UV-induced tolerance to contact allergens. This contrasts with normal individuals who can develop contact hypersensitivity after UV exposure.
What genetic factors are associated with PMLE?
PMLE is indicated to have a polygenic inheritance model. Familial clustering is observed, with a family history of PMLE present in 12% of first-degree relatives of affected individuals. Additionally, a 21% prevalence of photosensitivity was noted among first-degree relatives of PMLE patients.
What hormonal factors may influence the incidence of PMLE in women?
Females are described as being relatively resistant to the immunosuppressive effects of UV radiation, requiring more than three times the amount of UV exposure to achieve the same level of immune suppression as men. This may contribute to the higher incidence of PMLE in women. The hormone 17β-estradiol is also suggested to play a role by preventing UV-induced immune suppression.
What is the relationship between PMLE and skin cancer prevalence?
Patients with PMLE show a lower prevalence of skin cancer compared to matched controls, suggesting that PMLE may act as a protective condition against skin cancer. This is consistent with the reported resistance to UV-induced immune suppression in PMLE patients.
A patient with PMLE has a positive family history of photosensitivity. What percentage of PMLE patients typically report a positive family history?
Approximately 20% of PMLE patients report a positive family history.
