ObjectiveInclusion body myositis (IBM) is characterized by a combination of inflammatory and degenerative changes affecting muscle. While the primary cause of IBM is unknown, genetic factors may influence disease susceptibility. To determine genetic factors contributing to the etiology of IBM, we conducted the largest genetic association study of the disease to date, investigating immune‐related genes using the Immunochip.MethodsA total of 252 Caucasian patients with IBM were recruited from 11 countries through the Myositis Genetics Consortium and compared with 1,008 ethnically matched controls. Classic HLA alleles and amino acids were imputed using SNP2HLA.ResultsThe HLA region was confirmed as the most strongly associated region in IBM (P = 3.58 × 10−33). HLA imputation identified 3 independent associations (with HLA–DRB1*03:01, DRB1*01:01, and DRB1*13:01), although the strongest association was with amino acid positions 26 and 11 of the HLA–DRB1 molecule. No association with anti–cytosolic 5′‐nucleotidase 1A–positive status was found independent of HLA–DRB1*03:01. There was no association of HLA genotypes with age at onset of IBM. Three non‐HLA regions reached suggestive significance, including the chromosome 3 p21.31 region, an established risk locus for autoimmune disease, where a frameshift mutation in CCR5 is thought to be the causal variant.ConclusionThis is the largest, most comprehensive genetic association study to date in IBM. The data confirm that HLA is the most strongly associated region and identifies novel amino acid associations that may explain the risk in this locus. These amino acid associations differentiate IBM from polymyositis and dermatomyositis and may determine properties of the peptide‐binding groove, allowing it to preferentially bind autoantigenic peptides. A novel suggestive association within the chromosome 3 p21.31 region suggests a role for CCR5.

Carotid body tumours (CBT) are the most common tumours at the carotid bifurcation. Widening of the bifurcation is usually demonstrated on conventional angiography. This sign may also be produced by a schwannoma of the cervical sympathetic plexus. A 45-year-old patient presented with a neck mass. Investigations included contrast-enhanced CT, MRI and magnetic resonance arteriography with contrast enhancement. Radiologically, the mass was considered to be a CBT due to vascular enhancement and splaying of the internal and external carotid arteries. Intraoperatively, it was determined to be a cervical sympathetic chain schwannoma (CSCS). The patient had a postoperative complication of first-bite syndrome (FBS).Although rare, CSCS should be considered in the differential diagnosis for tumours at the carotid bifurcation. Damage to the sympathetic innervation to the parotid gland can result in severe postoperative pain characterised by FBS and should be considered in all patients undergoing surgery involving the parapharyngeal space.

Splenic rupture is a rare but potentially fatal complication of infectious mononucleosis. Athletes returning to contact sports following infectious mononucleosis are at potential risk of splenic rupture secondary to abdominal trauma. No clear consensus exists as to when it is safe to allow these athletes return to contact sports. Suggested periods of abstinence have ranged from 2 weeks to 6 months. We outline our experiences with the use of abdominal ultrasonography at 1 month aft er the diagnosis of infectious mononucleosis as a means of determining when athletes can safely return to contact sports. Our study group was made up of 19 such patients (mean age: 16.7 yr). We found that 16 of these patients (84%) had normal splenic dimensions on ultrasonography 1 month aft er diagnosis, and they were therefore allowed return to contact sports. While the remaining 3 patients had an enlarged spleen at 1 month, their splenic dimensions had all returned to normal when ultrasonographic examination was repeated at 2 months postdiagnosis. We conclude that serial abdominal ultrasonography allows for informed decision making in determining when athletes can safely return to contact sports following infectious mononucleosis.