Related Experiment Video
Updated: Dec 8, 2025

Technique of Conjunctival Biopsy and Direct Immunofluorescence for Diagnosing Mucous Membrane Pemphigoid
Published on: June 17, 2025
Thiopurine S-methyltransferase and Pemphigus Vulgaris: A Phenotype-Genotype Study
Maral Mokhtari1, Farzaneh Mostanbet1, Saideh Nekooee Fard1
1Pathology Department, Shahid Faghihi Hospital, Shiraz University of Medical Sciences, Shiraz, Iran.
Background & Objective:
Thiopurine drugs are considered as a treatment modality in various autoimmune disorders including pemphigus vulgaris (PV). These drugs are metabolized by an enzyme "Thiopurine S-methyl transferase" (TPMT). Various variants of this enzyme may have decreased activity leading to serious drug side effects. To investigate the phenotype and genotype of TPMT in PV patients receiving thiopurine drugs.
Methods:
A total of 50 patients (29 women and 21 men) with pemphigus vulgaris treating with standard dose of Thiopurine drugs were selected. Sex, age, result of liver function test and complete blood count were recorded. Genotyping of two common non-functional allele (TPMT*2 and TPMT*3C) by Allele-specific and RFLP-PCR was performed. TPMT enzymatic level was determined by an ELISA based method.
Results:
Of patients, 36 (72%) were found to have normal TPMT level; and 12, (24%) had higher level of enzyme and 2, 4% had low TPMT enzyme, but none of the patients showed mutant TPMT*2 and TPMT*3C alleles. None of the patients showed hepatotoxicity and bone marrow suppression.
Conclusion:
The phenotypic assay based on ELISA method may have false positive and misleading results but genotyping using PCR-RFLP and allele specific PCR is accurate, simple and cost-effective and can be used in patients decided to undergo thiopurine treatment.
Related Concept Videos
Pleiotropy
Pedigree Analysis
Epistasis
Background and Environment Affect Phenotype
An example of how genetic background affects phenotype can be seen in horses. The Extension gene in horses is responsible for their coat color. A wild-type gene (EE) produces black pigment in the coat, while a mutant gene (ee) produces red pigment. A...
Epistasis Analysis

