Increased risk of persistent neuropathic pain after traumatic nerve injury and surgery for carriers of a human leukocyte antigen haplotype.

It is not known why some patients develop persistent pain after nerve trauma while others do not. Among multiple risk factors for the development of persistent posttrauma and postsurgical pain, a neuropathic mechanism due to iatrogenic nerve lesion has been proposed as the major cause of these conditions. Because there is some evidence that the human leukocyte antigen (HLA) system plays a role in persistent postsurgical pain, this study aimed to identify the genetic risk factors, specifically among HLA loci, associated with chronic neuropathic pain after traumatic nerve injuries and surgery in the upper extremities. Blood samples were taken to investigate the contribution of HLA alleles (ie, HLA-A, HLA-B, HLA-DRB1, HLA-DQB1, and HLA-DPB1) in a group of patients with persistent neuropathic pain (n = 70) and a group of patients with neuropathy without pain (n = 61). All subjects had intraoperatively verified nerve damage in the upper extremity. They underwent bedside clinical neurological examination to identify the neuropathic pain component according to the present grading system of neuropathic pain. Statistical analyses on the allele and haplotype were conducted using the BIGDAWG package. We found that the HLA haplotype A02:01-B15:01-C03:04-DRB104:01-DQB1*03:02 was associated with an increased risk of developing persistent neuropathic pain in the upper extremity (OR = 9.31 [95% CI 1.28-406.45], P < 0.05). No significant associations were found on an allele level when correcting for multiple testing. Further studies are needed to investigate whether this association is on a haplotypic level or if certain alleles may be causing the association.