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Fitzpatrick's Dermatology, 9th Edition (Chapter-based Decks) > 96: Solar Urticaria > Flashcards

96: Solar Urticaria Flashcards

1
Q

What are the clinical features of Solar Urticaria (SolU)?

A

Characterized by erythema and itchy wheals that develop rapidly at skin sites exposed to sun or artificial light.

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2
Q

What is the typical duration of Solar Urticaria symptoms after cessation of light exposure?

A

Symptoms typically disappear within 1 to 24 hours after cessation of light exposure.

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3
Q

How quickly do wheals develop in Solar Urticaria after exposure?

A

Wheals develop within a few minutes up to an hour of exposure.

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4
Q

Which skin areas are typically affected by Solar Urticaria?

A

Skin areas that are normally shielded by clothing.

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5
Q

Who is predominantly affected by Solar Urticaria?

A

Women in the third decade of life.

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6
Q

What is the epidemiology of Solar Urticaria?

A

Predominantly affects women in the third decade of life, with symptoms often presenting during spring to autumn.

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7
Q

What is the definition of Solar Urticaria (SolU)?

A

Solar urticaria (SolU) is the appearance of a whealing response within minutes of exposure to sunlight.

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8
Q

What is the primary cause of Solar Urticaria?

A

The cause is usually unknown, making it a primary condition.

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9
Q

What are the rare conditions linked to Solar Urticaria?

A

Cutaneous Porphyria (CP) and Systemic Lupus Erythematosus (SLE).

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10
Q

What causes the symptoms of Solar Urticaria?

A

Degranulation of skin mast cells and the release of histamine and other pro-inflammatory mediators.

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11
Q

What is the role of mast cells in the pathogenesis of Solar Urticaria?

A

Mast cells degranulate upon exposure to light, releasing histamine and other pro-inflammatory mediators.

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12
Q

What wavelengths of light are associated with skin mast cell degranulation in Solar Urticaria (SolU)?

A

UVA (320 to 400 nm), visible light (400 to 600 nm), UVB (280 to 320 nm), and rarely infrared (>600 nm).

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13
Q

What are the generalized signs and symptoms of systemic involvement in Solar Urticaria?

A

Malaise, nausea, dizziness, headaches, wheezing, dyspnea, loss of consciousness, and anaphylactic shock.

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14
Q

What is the significance of phototesting in the diagnosis of Solar Urticaria (SolU)?

A

Phototesting is essential for confirming the diagnosis of SolU and assessing disease activity.

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15
Q

What indicates a positive result in phototesting for Solar Urticaria (SolU)?

A

The test is considered positive if the test site exhibits a palpable and clearly visible itchy wheal and flare reaction at 10 minutes after phototesting.

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16
Q

What are the histopathological features of Solar Urticaria (SolU) skin lesions?

A

Within the first hours after irradiation, lesions show vasodilation, edema, and perivascular neutrophils and eosinophils in the upper dermis.

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17
Q

What are the key diagnostic criteria for Solar Urticaria (SolU)?

A

Patients with a history of rapid itching and whealing after light exposure should be investigated for SolU.

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18
Q

What laboratory tests are relevant for diagnosing Solar Urticaria (SolU)?

A

Tests for antinuclear antibody (ANA) and extractable antinuclear antibody (ENA) should be conducted to exclude porphyria and systemic lupus erythematosus (SLE).

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19
Q

What are the limitations of routine laboratory tests in diagnosing Solar Urticaria?

A

Routine laboratory tests are within normal limits and not helpful for diagnosing Solar Urticaria.

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20
Q

What are the potential reasons for refractoriness of the skin during phototesting in Solar Urticaria?

A

Refractoriness may occur due to prior light exposure of the test site, reducing the skin’s sensitivity to phototesting.

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21
Q

What is the significance of the minimal urticarial dose in Solar Urticaria?

A

The minimal urticarial dose is a marker of disease activity and response to therapy, determined through threshold testing during phototesting.

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22
Q

What is the difference between primary and secondary Solar Urticaria?

A

Primary Solar Urticaria has an unknown cause, while secondary Solar Urticaria is very rarely linked to conditions like cutaneous porphyria (CP) or systemic lupus erythematosus (SLE).

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23
Q

What is the clinical relevance of bruised skin being more sensitive to light in some Solar Urticaria patients?

A

This sensitivity suggests that localized skin changes may alter the threshold for light-induced whealing.

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24
Q

What is the clinical significance of erythema in Solar Urticaria?

A

Erythema is caused by vasodilation due to the release of histamine and other mediators from mast cells.

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25
Q

A patient with Solar Urticaria reports symptoms only during spring and autumn. Is this common?

A

Yes, some patients with Solar Urticaria present symptoms during spring to autumn.

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26
Q

A patient with Solar Urticaria has a history of bruised skin being more sensitive to light. What does this suggest about their condition?

A

This suggests that bruised skin in some Solar Urticaria patients may have increased sensitivity to light.

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27
Q

What are the systemic symptoms that may occur in severe cases of Solar Urticaria?

A

Systemic symptoms include malaise, nausea, dizziness, headaches, wheezing, dyspnea, loss of consciousness, and anaphylactic shock.

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28
Q

What are the risk factors for developing Solar Urticaria?

A

Risk factors include being female, with a peak age of onset between 20 and 40 years.

29
Q

What is the importance of determining the inhibition spectrum in Solar Urticaria?

A

Determining the inhibition spectrum helps identify wavelengths that inhibit whealing, which can guide management strategies.

30
Q

A patient with a convincing history of light-induced whealing has a negative phototest. What are possible reasons for this result?

A

Possible reasons for a negative phototest include mild disease activity, prior intake of antihistamines or medications that inhibit wheal development, or refractoriness of the skin due to previous light exposure.

31
Q

What wavelengths of light are most commonly associated with triggering Solar Urticaria?

A

Solar Urticaria is most commonly triggered by UVA (320–400 nm) and visible light (400–600 nm).

32
Q

What is the so-called inhibition spectrum in relation to Solar Urticaria?

A

It refers to skin exposure to distinct wavelength radiation that can inhibit whealing in response to the eliciting wavelength spectrum.

33
Q

What should be investigated in patients with rapid itching and whealing after light exposure?

A

They should be investigated for Solar Urticaria (SolU).

34
Q

What is the role of phototesting in Solar Urticaria?

A

Phototesting is essential for confirming the diagnosis of SolU and assessing disease activity.

35
Q

What are the typical findings in SolU skin lesions shortly after irradiation?

A

They show vasodilation, edema, and perivascular neutrophils and eosinophils in the upper dermis.

36
Q

What laboratory tests are helpful for diagnosing Solar Urticaria?

A

Routine laboratory tests are not helpful; tests for porphyria and SLE should be conducted instead.

37
Q

What indicates a positive phototest result?

A

A palpable and clearly visible itchy wheal and flare reaction at 10 minutes after phototesting.

38
Q

What should be done if a patient has a negative phototest but a convincing history of light-induced whealing?

A

Solar Urticaria should not be excluded, and sunlight phototesting is recommended.

39
Q

What are the reasons for a negative phototest result?

A

Reasons include mild disease activity, prior intake of antihistamines, or skin refractoriness due to previous light exposure.

40
Q

What is the significance of threshold testing in phototesting?

A

It determines the minimal urticarial dose, a marker of disease activity and response to therapy.

41
Q

What should be asked of patients reporting sunlight-induced skin lesions?

A

They should be asked if the lesions resemble wheals and if they are itchy, accompanied by erythema, short-lived, and transient.

42
Q

What is the first step in the diagnostic algorithm for solar urticaria?

A

The first step is to assess the occurrence of signs and symptoms within minutes after sunlight exposure.

43
Q

What should be ruled out if the first symptoms of solar urticaria occur in early childhood?

A

If the first symptoms occur in early childhood, one should rule out erythropoietic protoporphyria by determining protophorphyrin levels in erythrocytes.

44
Q

What is the significance of phototesting in the diagnostic algorithm for solar urticaria?

A

Phototesting is significant as it helps determine if wheals occur within minutes after testing, which is a key indicator in the diagnostic process.

45
Q

What are the distinguishing features of polymorphic light eruption?

A

Distinguishing features include skin lesions that appear as papules, papulovesicles, or eczematous appearance, occurring within hours to days after UV exposure and resolving within several days.

46
Q

What common feature is shared by lupus erythematosus and solar urticaria?

A

Both conditions can present with skin lesions that may have a wheal-like appearance after UV exposure.

47
Q

What is a distinguishing feature of photoexacerbated eczema?

A

A distinguishing feature is that there are no wheals; skin lesions occur within hours to days after UV exposure and resolve within several days.

48
Q

What is the common feature of drug or chemical photosensitivity?

A

The common feature is that skin lesions occur within hours to days after UV exposure and resolve within several days.

49
Q

What is the mean duration of Solar Urticaria (SolU)?

A

The mean duration of Solar Urticaria (SolU) is 5 to 7 years, with durations reported up to 50 years.

50
Q

What is the recommended first-line treatment for Solar Urticaria?

A

The recommended first-line treatment for Solar Urticaria is nonsedating H1 antihistamines at standard doses.

51
Q

What should be done if there is insufficient response to standard-dosed nonsedating second generation antihistamines?

A

If there is insufficient response, the doses of nonsedating second generation antihistamines should be increased up to 4-fold.

52
Q

What is the role of omalizumab in the treatment of Solar Urticaria?

A

Omalizumab, a monoclonal antibody directed against IgE, is recommended for patients who do not achieve sufficient control with the combined use of sunscreens and antihistamine treatment.

53
Q

What are the risks associated with phototherapy for Solar Urticaria?

A

Phototherapy carries the usual risks of long-term treatment and should be done with caution due to the risk of anaphylaxis, particularly in severely affected individuals.

54
Q

What precautions should Solar Urticaria patients take to avoid triggers?

A

Solar Urticaria patients should avoid the sun, wear protective clothing, and use high-protection broad-spectrum sunscreens.

55
Q

What is the median duration from disease onset to resolution for Solar Urticaria?

A

The median duration from disease onset to disease resolution for Solar Urticaria is 63 months.

56
Q

What is the importance of continuing phototherapy in Solar Urticaria treatment?

A

Continuing phototherapy is important to maintain its effect, as discontinuation results in the loss of protection from light-induced whealing.

57
Q

How can patients prevent the development of Solar Urticaria signs and symptoms?

A

Patients can prevent the development of Solar Urticaria signs and symptoms by avoiding sun exposure and using high protection factor broad-spectrum sunscreens and appropriate clothing.

58
Q

What is the first step in the treatment algorithm for solar urticaria?

A

The first step is to use second-generation H1-antihistamines (sgAH). If there is inadequate control after 2 to 4 weeks or earlier if symptoms are intolerable, further steps are needed.

59
Q

What should be done if the second-generation H1-antihistamine does not provide adequate control for solar urticaria?

A

If inadequate control is observed, the next step is to increase the sgAH dose (up to 4 times). If this still does not provide adequate control after 2 to 4 weeks or if symptoms are intolerable, additional treatments should be considered.

60
Q

What are the options to add on if increasing the sgAH dose is not effective for solar urticaria?

A

If increasing the sgAH dose does not provide adequate control, options to add on include: 1. Omalizumab 2. Cyclosporin.

61
Q

What additional treatment options are available for solar urticaria beyond the main algorithm?

A

Additional treatment options include: Phototherapy (UV-hardening), intravenous immunoglobulins, antimalarials, plasmapheresis.

62
Q

What happens if phototherapy is discontinued in Solar Urticaria patients?

A

It results in the loss of protection from light induced whealing.

63
Q

What counseling advice is given to prevent the development of Solar Urticaria signs and symptoms?

A

Avoidance of sun exposure and use of high protection factor broad-spectrum sunscreens and appropriate clothing.

64
Q

What is a key procedure to achieve tolerance to UV light in Solar Urticaria patients?

A

Desensitization achieved by phototherapy.

65
Q

What is a key characteristic of erythropoietic protoporphyria?

A

Skin lesions are painful and burning, persisting for hours after UV exposure.

66
Q

What does a negative phototesting result indicate in the context of solar urticaria?

A

It suggests that further testing is needed to rule out other conditions, as it may not be indicative of solar urticaria.

67
Q

How often can omalizumab be administered for Solar Urticaria?

A

Doses of up to 450 mg every 4 to 8 weeks have been reported.

68
Q

What is the role of broad-spectrum sunscreens in managing Solar Urticaria?

A

Broad-spectrum sunscreens help prevent the development of Solar Urticaria signs and symptoms by blocking harmful wavelengths of light.

Fitzpatrick's Dermatology, 9th Edition (Chapter-based Decks) (48 decks)

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