Porphyrin Metabolism Disorders

 Porphyria cutanea tarda (PCT) and erythropoietic protoporphyria (EP) associated with hepatic pathology



• Terms “hepatic” or “erythropoietic” porphyria based on site of heme precursor accumulation




Etiology/Pathogenesis




• Genetic: Defect in 1 of 8 enzymes involved in heme synthesis
image EP due to partial deficiency of ferrochelatase activity

image Familial PCT due to deficiency of uroporphyrinogen decarboxylase activity in all tissues

• Sporadic PCT is primarily an acquired disorder
image Precipitating factors include hepatitis C virus (HCV), HFE mutations, alcohol, and drugs


Clinical Issues




• Photosensitivity, variable liver disease


Microscopic




• PCT: Mild to moderate siderosis, steatosis, changes typical of HCV

• EP: Cholestasis; red-brown aggregates of protoporphyrin in canaliculi, hepatocytes, Kupffer cells


Ancillary Tests




• PCT
image Electron microscopy

image Polarization microscopy

image Ferric ferricyanide stain

image Laboratory testing for porphyrins

• EP
image Electron microscopy

image Polarization microscopy

image Laboratory testing for porphyrins

image
Cholestasis and Deposits in EP
Erythropoietic protoporphyria (EP) features cholestasis and rust-brown deposits image in both hepatocytes and canaliculi.


image
Maltese Crosses of EP Under Polarized Light
When viewed under polarized light, EP shows birefringent protoporphyrin deposits that are brightly birefringent and have a Maltese cross appearance image .

image
Maltese Crosses of EP Under Polarized Light
When viewed under polarized light, protoporphyrin deposits exhibit the characteristic Maltese cross configuration image. Additional red-brown protoporphyrin deposits image are also visible.

image
Low-Power View
H&E-stained slide shows a background of mild steatosis image, mild portal inflammation image, and hepatocyte swelling image in a patient with EP. The red-brown protoporphyrin deposits image are also visible.


TERMINOLOGY


Abbreviations




• Porphyria cutanea tarda (PCT)

• Erythropoietic protoporphyria (EP)


Synonyms




• EP also termed erythrohepatic protoporphyria and protoporphyria


Definitions




• Heterogeneous set of disorders of heme biosynthesis, resulting in accumulation of heme precursors
image PCT and EP are associated with hepatic pathology

• Terms “hepatic” or “erythropoietic” porphyria based on site of heme precursor accumulation


ETIOLOGY/PATHOGENESIS


Genetic Disorder: EP and Type II (Familial) PCT




• Defect in 1 of 8 enzymes involved in heme synthesis
• EP: Partial deficiency of ferrochelatase activity

• Type II (familial) PCT: 20% of PCT patients

image Heterozygous uroporphyrinogen decarboxylase ( UROD ) mutation

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Apr 20, 2017 | Posted by in PATHOLOGY & LABORATORY MEDICINE | Comments Off on Porphyrin Metabolism Disorders

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