Severe Neutropenia and Agranulocytosis Related to Antithyroid Drugs: A Study of 30 Cases Managed in A Single Reference Center

Novel Association of KLRC4-KLRK1 Gene Polymorphisms with Susceptibility and Progression of Antithyroid Drug-Induced Agranulocytosis

OBJECTIVE

Antithyroid drug (ATD)-induced agranulocytosis (TIA) is the most serious adverse effect during ATD treatment of Graves' disease (GD). Previously, the MICA gene was reported to be associated with TIA. MICA protein is an important ligand for the NKG2D protein, which is encoded by the KLRK1 gene and KLRC4-KLRK1 read-through transcription. This study further investigated the association between KLRC4-KLRK1 gene polymorphisms and susceptibility to TIA.

METHODS

Twenty-eight candidate single nucleotide polymorphisms (SNPs) on KLRC4-KLRK1 read-through transcription were evaluated by the iPLEX MassARRAY system in 209 GD control patients and 38 TIA cases.

RESULTS

A significant association of rs2734565 polymorphism with TIA was found (p=0.02, OR=1.80, 95% CI=1.09-2.96). The haplotype C-A-A-C-G, including rs2734565-C, was associated with a significantly higher risk of TIA (p=4.79E-09, OR=8.361, 95% CI=3.737-18.707). In addition, the interval time from hyperthyroidism to agranulocytosis onset was shorter in patients carrying the rs2734565-C allele than in non-carrying groups (45.00 (14.00-6570.00) d vs. 1080.00 (30.00-3600.00) d, p=0.046), and the interval from ATD treatment to agranulocytosis onset was also shorter in patients carrying rs2734565-C allele (29.00 (13.00-75.00) d vs. 57.50 (21.00-240.00) d, p=0.023).

CONCLUSIONS

The findings suggest that the KLRC4-KLRK1 gene polymorphism is associated with susceptibility and progression of ATD-induced agranulocytosis. Patients carrying the rs2734565-C allele had a higher susceptibility and faster onset time of TIA.

Medical treatment of thyrotoxicosis

Medical treatment is the primary therapeutic option for thyrotoxicosis/hyperthyroidism. Two groups of causes of thyrotoxicosis (i.e. thyrotoxicosis with hyperthyroidism and thyrotoxicosis without hyperthyroidism) need to be considered for therapeutic reasons. Herein we provide an updated review on the role of conventional medical therapies (i.e. β-blockers, antithyroid drugs [ATDs], corticosteroids, inorganic iodide, perchlorate, cholecystographic agents, lithium, cholestyramine) in the main causes of thyrotoxicosis, starting from the rationale subtending their clinical application.