• rss
  • facebook
  • twitter
  • linkedin

Winning Abstracts from the 2007 Medical Student Abstract Competition: Porphyria Cutanea Tarda (Pct): Mutations and Sequence Variants in the Uroporphyrinogen Decarboxylase (Uro-D) Gene in Sporadic Patients.

.

Author:
Eric Gehrie, Mount Sinai School of Medicine

Introduction:
Porphyria cutanea tarda (PCT), the most common disorder of heme biosynthesis, typically presents with characteristic light-induced blistering skin lesions. Familial PCT (F-PCT) is an autosomal dominant disorder and patients have germline uroporphyrinogen decarboxylase (URO-D) mutations, half-normal erythrocyte and decreased hepatic URO-D activities. In contrast, sporadic PCT (S-PCT) patients have normal UROD genes and erythrocyte URO-D activities, but have decreased hepatic URO-D activity presumably due to the specific inhibition of the hepatic enzyme. Both familial and sporadic forms are precipitated by environmental factors including alcohol, iron overload, and viral infections (e.g., HCV). S-PCT and F-PCT can be diagnosed biochemically by markedly elevated urinary heptacarboxylate porphyrin levels.

Methods:
To determine if URO-D single nucleotide polymorphisms (SNPs) or rare sequence variants predispose to S-PCT, the entire ~3.5 kb URO-D gene and 1000 bases upstream and downstream were sequenced in 24 sporadic patients who had no affected relatives, and 25 unrelated normal individuals.

Results:
Surprisingly, two previously identified URO-D coding mutations, R142X and a complex mutation (g645del1053ins10), were identified in 2 (8.3%) unrelated S-PCT patients, indicating that they actually had F-PCT. At-risk relatives have been counseled and offered testing. In addition, studies of a known F-PCT family revealed a novel URO-D mutation (H331R). Among the 22 S-PCT patients, 8 SNPs were identified at gDNA -293 (4 patients), -263 (9), -175 (1),496 (9), 1562 (2), 1772 (2), 1835 (9), and 2892 (9). The three F-PCT patients had 5 SNPs at gDNA -263 (2), 496 (10), 1835 (2), 2892 (2), and 3236 (1). In the 25 control patients, 7 SNPs were identified at gDNA -293 (6), -263 (10), 496 (10), 1562 (2), 1772 (2), 1835 (10), and 2892 (10).

Conclusion:
This is the first report of germline mutations in presumed S-PCT patients, indicating that these manifesting patients either had de novo mutations or F-PCT that masqueraded as S-PCT due to the low penetrance of the germline mutations. Therefore, biochemically confirmed S-PCT patients should be screened by mutation analysis. In addition, no sequence variants or SNPs were identified in the URO-D gene that predisposed patients to S-PCT.

Back to October 2007 Issue of IMpact

More Articles Like This

Students: Join ACP for Free

Benefits of Membership for Students: ACP's free Medical Student Membership includes benefits designed especially to meet students' needs.

Join Now: Sign-up today and begin enjoying the benefits of ACP Medical Student Membership.

Find a Residency

Search ACP's Internal Medicine Residency Database for information on all internal medicine residency programs in the U.S. and Canada. (ACP Members only)

More search options

Share this article

Bookmark and Share

MKSAP 16 Holiday Special: Save 10%

MKSAP 16 Holiday Special:  Save 10%

Use MKSAP 16® to earn MOC points, prepare for ABIM exams and assess your clinical knowledge. For a limited time save 10% when you use priority code MKPROMO! Order now.

Maintenance of Certification:

What if I Still Don't Know Where to Start?

Maintenance of Certification: What if I Still Don't Know Where to Start?

Because the rules are complex and may apply differently depending on when you last certified, ACP has developed a MOC Navigator. This FREE tool can help you understand the impact of MOC, review requirements, guide you in selecting ways to meet the requirements, show you how to enroll, and more. Start navigating now.