Practice Question Answers: Porphyrias
This fact sheet reviewed porphyrias. The porphyrias encompass a group of both inherited and acquired metabolic disorders resulting from the dysfunction of enzymes involved in the heme biosynthesis pathway. The porphyrias often have overlapping clinical features, making the knowledge of the laboratory workup essential in distinguishing between them. Included here are the answers to the practice questions. (Registration is required to view the answers.)
1. Which of the following enzymes of the heme synthesis pathway is found in the mitochondria?
a. δ-aminolevulinic oxidase
b. porphobilinogen deaminase
,c. protoporphyrinogen oxidase
d. uroporphyrinogen decarboxylase
e. uroporphyrinogen III synthase
2. A patient with variegate porphyria uniquely has plasma fluorescence at the following wavelength:
a. 311 nm
b. 366 nm
c. 410 nm
d. 626 nm
e. 630 nm
3. What laboratory result would be expected to be abnormal in a patient with a defect in ferrochelatase?
a. elevated δ-aminolevulinic acid
b. elevated erythrocyte protoporphyrins
c. elevated fecal coproporphyrins
d. elevated urinary porphobilinogen
e. elevated urinary uroporphyrins
4. What clinical feature would be present in a newborn diagnosed with transient erythroporphyria of infancy?
a. dark red urine
b. immediate burning photosensitivity
c. red teeth that fluoresce under Wood lamp
d. skin purpura
e. urine that fluoresces pink under Wood lamp
5. What medication should be avoided in a patient with a defect in porphobilinogen deaminase?
a. captopril
b. furosemide
c. griseofulvin
d. naproxen
e. tetracyclines