A 20 y.o. male comes in with a rash on his ears and swelling of the hands and feet.
He reports the rash is always worse in the spring.
A 20 y.o. patient comes in with swelling of the hands and feet and a rash on his ears. He reports his ears tend to break out in spring.
The differential here includes rashes caused by exposure to light.
1. PRIMARY PHOTODERMATOSES
The causes of idiopathic photodermatoses have not yet been discovered but light is the trigger and an allergic reaction develops.
--These are rashes triggered by sensitivity to light in the UV spectrum. This can be triggered by sunlight or exposure to a tanning bed. The reaction causes an immune response leading to a rash. Sensitive individuals can react to either UVA or UVB or both. UVA does not penetrate glass but UVB does.
A well known sun-induced condition is called juvenile spring eruption and it is a rash appearing on the ears usually in boys and young men early in spring. 8-24 hours after sun exposure. Blisters can develop on the ears.
Juvenile spring eruption
2. EXOGENOUS PHOTODERMATOSES
These reactions are caused by an external source.
--UV light can also a direct toxic effect on the skin of individuals taking tetracycline, griseofulvin, drugs containing retinoic acid used for acne, NSAIDS, chemotherapy or sulfonamides. Diuretics, antidepressants, and benzodiazepines have also been implicated.
--UV light can trigger allergic reaction to the skin when chemicals have been applied like fragrances, plant psoralens or sunscreens wiith PABA. Lime in a margarita can trigger photosensitivity. Psoralens have been treated since ancient times to treat vitiligo since the reaction causes hyperpigmentation.
Lime is a well known photosensitizer
3. PHOTO-EXACERBATED DERMATOSES
These are underlying conditions which make the skin more sensitive to light.
--Niacin deficiency or pellagra makes the skin more sensitive to light.
--lupus, psoriasis and porphyria are well known causes of photodermatitis.
In porphyria cutanea tarda accumulation of iron or uroporphyrin( PBG spontaneously converts urine to a reddish color on exposure to light) in the skin is thought to trigger the reaction. Porphyrins in the skin cause light to enter an excited state and release photons that active oxygen to higher energy singlet oxygen which damages proteins causing blistering . This is often associated with liver disease and found in alcoholics.
HIV associated with porphyria cutanea tarda
--Lupus often causes a malar rash. Research has shown this may be due to an increase in interferon kappa generated in keratinocytes.
Considering the possibilities for our patient he was at first thought by derm to have a juvenile spring eruption but labs were sent.
He was found to have lupus as the labs below indicate and was treated with immunosuppression which relieved his symptoms.
Double stranded DNA > 300
ANA 1:1280
ENA >8 nl <.9
RNP 6.3 nl is <1
CRP 48 nl < 10
Argila D, Auilera J, Sanchez J, et al. Study of idiopathic, exogenous photodermatoses. Part 1: pathophysiology and technical aspects of photobiologic studies. Actas Dermo-Sifiliografican(English Edition) 2014 Vol 105(2):112-121.
Oakley A, Badri T, Harris B. Photosensitivity StatPearls 2021
Abramowitz A, Resnik K , Cohen K. Margarita photodermatitis (March 1993) NEJM 328(12)891.
Kakoullis L, Loupides S, Papachistodoulou E, et al. Porphyrias and photosensitivity: pathophysiology for the clinician. Postgrad Med 2018 Nov;130(8):673-686.
Lim H, Mechanisms of phototoxicity in porphyria cutanea tarda and erythropoictic protoporphyria. 1989. Immunol Ser. 46:671-85.
Guha S, Bandyopadhyay D, Saha A, et al. Human immunodeficiency virus associated sporadic nonfamilial porphyria cutanea tarda. 2016. Indian Journal of Dermatology Volume 61(3):318-320.
Pellagra (niacin deficiency ) is also associated with photosensitivity