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2015-01-29 20:24:20
porphyrins porphyria

Things not covered in my other units that are pertinent to the ASCP exam.
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  1. What is porphyria?
    A disturbance in heme synthesis.  The primary cause is an enzyme deficiency.
  2. Name two precursors to porphyrin.
    Porphobilinogen and δ-aminolevolinic acid (ALA)
  3. Name three clinically important porphyrins.
    • 1. protoporphyrin (excreted in feces)
    • 2. uroporphyrin (excreted in urine)
    • 3. coproporphyrin (excreted in feces and urine)
  4. What are the porphyrins that can be extracted from RBCs?
    Free Erythrocyte porphyrins (FEP)

    • *Protoporphyrin is the primary one.
    • *Seen in persons with lead poisoning or iron-deficiency anemia.
  5. What are the two classes of porphyria?
    • Neurologic Porphyria - abdominal pain, psychotic behavior, neuromuscular difficulties.
    •     ↑ ALA and porphobilinogen levels in urine.

    • Cutaneous Porphyria - excess porphyrins in skin; photosensitivity and skin lesions.
    •     Normal ALA and porphobilinogen urine levels.
  6. What are the three neurological porphyrias and their patterns?
    All have ↑ ALA and porphobilinogen levels in urine.

    • 1. Acute intermittent porphyria (most common)
    •      ↑ uroporphyrin levels

    • 2. Variegate porphyria (rare)
    •      ↑ protoporphyrin and coproporphyrin levels

    • 3. Coproporphyria (rare)
    •      ↑ coproporphyrin levels
  7. What are the three cutaneous porphyrias and their patterns?
    All have normal ALA and porphobilinogen urine levels.

    • 1. Congenital erythropoietic porphyria (rarest of inherited porphyrias)
    •      ↑ uroporphyrin and coproporphyrin levels

    • 2. Protoporphyria (somewhat rare)
    •      ↑ protoporphyrin and free erythrocyte protoporphyrin

    • 3. Porphyria cutanea tarda (most common) - appears in adults following liver disease or excessive alcohol intake.
    •      ↑ uroporphyrin levels