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erythropoietic protoporphyria (EPP)

An inherited photosensitivity disorder unique among the porphyrias in that porphyrins & their precursors are not excreted in the urine. It is also the only porphyria in which biochemical defects manifest themselves in erythropoietic & hepatic cells. Etiology: 1) deficiency in ferrochelatase 2) accumulation of protoporphyrin 4) overactivy of ALA synthetase appears to play a role 3) precipitated by exposure to UV-A radiation Epidemiology: 1) onset in childhood, rarely in early adulthood 2) no sex preference 3) all ethnic groups 4) prevalence 1:100,000 Pathology: 1) liver a) periportal fibrosis & deposits of brown pigment b) birefringent granules within hepatocytes & Kupffer cells c) increased protoporphyrin in liver 2) skin a) marked eosiniphilic homogenization & thickening of the blood vessels in the papillary dermis b) accumulation of an amorphous, hyaline-like eosinophilic substance in & around blood vessels Genetics: - associated with defects in ferrochelatase (FECH) Clinical manifestations: 1) skin manifestations - stinging & itching within a few minutes of sunlight exposure - delayed effects on skin 1-8 hours later - erythema, bright red - edema, especially of hands - urticaria, less common - purpura, especially nose & tips of ears - vesicles or bullae, rare - changes subside within several hours to days - resolution without scarring - no "rash", only exagerated & rapid "sunburn" response - symptoms may occur when exposed to sunlight through windows - chronic recurrent exposure - shallow, often linear scars, especially on nose & dorsal aspect of hands - diffuse wrinkling & waxy color of facial skin - crusted erosive lesion may occur on nose & lips - no sclerodermal-like changes, hirsuitism or hyperpigmentation 2) systemic manifestations - biliary colic (protoporphyrin cholelithiasis) may occur - hemolytic anemia with hypersplenism (rare) - hepatic cirrhosis & portal hypertension (20%) Laboratory: 1) increased protoporphyrin in erythrocytes 2) urine: no porphyrins or their precursors except in rare cases of fatal hepatic cirrhosis 3) increased protoporphyrin in feces 4) liver function tests 5) peripheral blood smear: transient fluorescence at 400 nm 6) liver biopsy if indicated 7) skin biopsy Radiology: gallstones may be present Complications: fatal hepatic cirrhosis Management: 1) prognosis a) lifelong condition, no curative therapy b) photosensitivity may become less prominent in older age 2) symptomatic therapy a) beta carotene 180 mg PO daily, divided BID/TID provides amelioration of the photosensitivity b) PUVA photochemotherapy may enhance the dephotosensitizing effect of beta carotene

Related

aminolevulinic acid [ALA] synthetase ferrochelatase, mitochondrial; heme synthase; protoheme ferro-lyase (FECH) heme synthesis protoporphyrin

General

porphyria

Properties

ACCUMULATION: protoporphyrin DEFICIENCY: ferrochelatase, mitochondrial

Database Correlations

OMIM 177000

References

  1. Williams Hematology, 5th edition, Beutler et al eds, McGraw-Hill, 1995 pg 740
  2. Color Atlas and Synopsis of Clinical Dermatology, Common and Serious Diseases, 3rd ed, Fitzpatrick et al, McGraw Hill, NY, 1997, pg 263-65
  3. Clinical Diagnosis & Management by Laboratory Methods, 19th edition, J.B. Henry (ed), W.B. Saunders Co., Philadelphia, PA. 1996, pg 172
  4. Mayo Internal Medicine Board Review, 1998-99, Prakash UBS (ed) Lippincott-Raven, Philadelphia, 1998, pg 178-79