Heme biosynthesis disorders

Question 1

Vitamin B6 deficiency results in ____.

Answer 1

reduced ALAS activity

microcytic hypochromic anemia

Question 2

What effect does lead toxicity have? Which enzymes are inhibited by lead?

Answer 2

anemia
ALA dehydratase and ferrochelatase inhibited
ALA and zinc protoporphyrin accumulate

Question 3

What are Porphyrias due to?

Answer 3

usually due to partial deficiency of a heme biosynthetic enzyme (any of the 8 affected)
accumulations of porphyrins and their precursors

Question 4

What are some signs and symptoms of porphyria?

Answer 4

purple or red urine / teeth

photosensitivity, skin lesions, increased hair growth, acute pain, neuropathy, vomiting, confusion

Question 5

How are porphyrias usually inherited?

Answer 5

Most autosomal dominant.

rare- autosomal recessive
some X linked dominant and recessive

penetrance is usually low; latent, silent

Question 6

What are the three most common porphyria?

Answer 6

porphyria cutanea tarda (most common)
uroporphyrinogen decarboxylase defective
20% genetic AD
80% triggered by liver damage

acute intermittent porphyria
porphobilinogen deaminase mutation
neurological symptoms can be severe
ALA and porphyrinogen in plasma (urine darkens on standing)

eryhtropoietic protoporphyria
ferrochelatase mutation
mostly skin symptoms

Question 7

How are porphyria’s class

Answer 7

site of heme precursor accumulation

• liver hepatic type (neuropsych problems)
• bone marrow erythropoieitic type (skin)

symptoms: acute, non acute, cutaneous
diagnose: blood urine stool sample tests