| • | pock-like scarring on the nose and cheeks in conjunction with a history of burning (sensation) shortly after exposure to sunlight suggests the diagnosis of EPP |
pathogenesis:
| • | ferrochelatase = defective enzyme; converts protoporphyrin to heme (AKA ferroprotoporphyrin) |
| • | the basic enzymatic defect is at the level of the bone marrow stem cell |
clinical:
| • | mean age of onset = 4 years |
| • | symptoms occur within a few minutes to 1 hour of exposure to sunlight |
| • | symptoms: burning and stinging, edematous urticaria-like plaques or eczematous areas may appear several hours later (vesicle or bullae rare) |
| • | chronic changes: variable severity; patient may show pock-like scarring on the nose and cheeks; shallow, linear or elliptical pits are seen particularly on face and dorsa of hands |
| • | waxy, thickened scarring over nose, face and back of hands (their skin looks like the waxy lesions of lipoid proteinosis) |
| • | liver disease, usually mild |
histology:
| • | amorphous, hyaline-like material in and around the dermal capillary walls |
| • | the hyaline material is histologically similar to that of lipoid proteinosis |
ddx:
| • | PMLE, solar urticaria (because onset after minutes of sun), hydroa vacciniforme (because of scars), Hutchinson’s summer prurigo |
| • | EPP is easily diagnosed when blood (plasma and erythrocyte) protoporphyrin is measured; diagnosis may be missed if only fecal and urinary porphyrin are estimated as these can both be normal in EPP (protoporphyria is poorly soluble in water and therefore not excreted in urine) |
treatment:
| • | sunscreens containing titanium dioxide |
| • | beta-carotene: (= provitamin A; i.e. precursor) a known quencher of free radical and singlet oxygen, has a photoprotective effect |
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