Modulation of clinical phenotype of Glanzmann's thrombasthenia by thrombogenic mutations

Glanzmann's thrombasthenia (GT) is an autosomal recessive bleeding disorder which is due to a defect in platelet aggregation in response to multiple physiological agonists. It has been demonstrated that the clinical phenotype of various diseases inherited in a classic Mendelian fashion can be modulated by a series of factors, inherited as well as acquired.

A total of 45 GT patients were screened for the thrombogenic polymorphisms, i.e., FV Leiden (R506Q), Prothrombin G20210A, MTHFR C677T and HPA-1 by PCR/RFLP.

MTHFR C677T heterozygous was seen in 6 patients, FV Leiden heterozygous in one and Prothrombin G20210A gene variant in none. HPA-1 was seen in 3 patients of whom 1 was homozygous and 2 were heterozygous.

Thus the coinheritance of heterozygous FV Leiden alone or homozygous HPA 1b alone or the combined heterozygosity of MTHFR and HPA-1 were predicted to alter the clinical phenotype. Whereas the inheritance of heterozygous MTHFR alone or heterozygous HPA-1 alone did not altered the clinical phenotype significantly. Hence FV Leiden, MTHFR C677T polymorphism along with PLA-1 and homozygous HPA-1 were the probable ameliorating factor in GT mild phenotype.