A genome-wide association study in autoimmune neurological syndromes with anti-GAD65 autoantibodies

Autoimmune neurological syndromes (AINS) with autoantibodies against the 65 kDa isoform of the glutamic acid decarboxylase (GAD65) present with limbic encephalitis, including temporal lobe seizures or epilepsy, cerebellitis with ataxia, and stiff-person-syndrome or overlap forms. Anti-GAD65 autoantibodies are also detected in autoimmune diabetes mellitus, which has a strong genetic susceptibility conferred by human leukocyte antigen (HLA) and non-HLA genomic regions. We investigated the genetic predisposition in patients with anti-GAD65 AINS. We performed a genome-wide association study (GWAS) and an association analysis of the HLA region in a large German cohort of 1214 individuals. These included 167 patients with anti-GAD65 AINS, recruited by the German Network for Research on Autoimmune Encephalitis (GENERATE), and 1047 individuals without neurological or endocrine disease as population-based controls. Predictions of protein expression changes based on GWAS findings were further explored and validated in the CSF proteome of a virtually independent cohort of 10 patients with GAD65-AINS and 10 controls. Our GWAS identified 16 genome-wide significant (P < 5 × 10-8) loci for the susceptibility to anti-GAD65 AINS. The top variant, rs2535288 [P = 4.42 × 10-16, odds ratio (OR) = 0.26, 95% confidence interval (CI) = 0.187-0.358], localized to an intergenic segment in the middle of the HLA class I region. The great majority of variants in these loci (>90%) mapped to non-coding regions of the genome. Over 40% of the variants have known regulatory functions on the expression of 48 genes in disease relevant cells and tissues, mainly CD4+ T cells and the cerebral cortex. The annotation of epigenomic marks suggested specificity for neural and immune cells. A network analysis of the implicated protein-coding genes highlighted the role of protein kinase C beta (PRKCB) and identified an enrichment of numerous biological pathways participating in immunity and neural function. Analysis of the classical HLA alleles and haplotypes showed no genome-wide significant associations. The strongest associations were found for the DQA1*03:01-DQB1*03:02-DRB1*04:01HLA haplotype (P = 4.39 × 10-4, OR = 2.5, 95%CI = 1.499-4.157) and DRB1*04:01 allele (P = 8.3 × 10-5, OR = 2.4, 95%CI = 1.548-3.682) identified in our cohort. As predicted, the CSF proteome showed differential levels of five proteins (HLA-A/B, C4A, ATG4D and NEO1) of expression quantitative trait loci genes from our GWAS in the CSF proteome of anti-GAD65 AINS. These findings suggest a strong genetic predisposition with direct functional implications for immunity and neural function in anti-GAD65 AINS, mainly conferred by genomic regions outside the classical HLA alleles.

Effects of knee compartment, concomitant surgery and smoking on medium-term outcome of microfracture

PURPOSE

The aim of this study was to determine the effect of compartment location, concomitant arthroscopic surgery and smoking on the medium-term outcome of knee microfracture.

METHODS

From a database of all 396 patients treated with microfracture for cartilage lesions in our Unit, details were taken of the 316 patients who met our inclusion criteria. Outcome was assessed by a self-administered postal questionnaire containing a general satisfaction question and a battery of four functional assessment scores. The rank sum of the four assessment scores was used as a single global functional outcome.

RESULTS

After two rounds of questionnaires 196 patients responded. Their average follow up was 37 months. In all, 72% of the patients were satisfied with their outcome and 19% were not. Patients with an affected lateral or patellofemoral compartment improved 1.5 SD, significantly more than those with an affected medial compartment who improved 1 SD. However, their satisfaction rates did not differ significantly. Having concomitant knee surgery did not significantly affect the functional outcome or satisfaction rate. Significantly fewer smokers than non-smokers were satisfied (54 vs 76%) and more dissatisfied (34 vs 15%), but differences in functional outcome were small and non-significant.

CONCLUSIONS

Patients with a lesion in the patellofemoral or lateral compartment have a significantly larger improvement than those with a medial compartment lesion. Satisfaction rates among these patients groups are however similar. Having concomitant arthroscopic knee surgery, in particular partial meniscectomies and ACL reconstruction, hardly affects the outcome of microfracture. Smoking is associated with a lower satisfaction rate although it has only a small effect on functional outcome. Finally, younger patients fare better than older patients although a cut-off point is hard to define. This information should help surgeons counsel patients better regarding prognosis and expectations after surgery.

Simultaneous traumatic rupture of the patellar tendon and the contralateral quadriceps tendon in a healthy individual

A simultaneous traumatic complete rupture of the patellar tendon and the contralateral quadriceps tendon is reported to occur in patients with renal failure and other inflammatory diseases, but is extremely rare in a healthy individual because of the different contributory factors and mechanisms of injury. We present a rare case report of such a combination of injuries in a 48-year-old healthy man. To our knowledge only three such cases have been reported in the English literature. This is an unusual combination and hence there is potential for missed diagnosis leading to suboptimal treatment.

Arthrosopic knot pushers. Does one size fit all?

Little is known about how knot-pusher design affects arthroscopic knot tying. In our practice, we observed the knot-pusher riding onto the arthroscopic knot at the point of maximum tightening. This can lead to snagging of the knot, which is undesirable as it may lead to loosening of, or damage to the knot. The aim of this study is to determine the optimum size of a knot-pusher to efficiently push the knot without overriding or snagging it. We used an apparatus to model arthropcopic knot tying. Ten examples each of the Duncan loop were tied under controlled conditions of load using one polydioxanone (PDS) monofilament absorbable suture (Ethicon, Livingston, UK), two Ethibond, two Fibrewire and two Panacryl. The loop of the knot was then secured and a 50 N force applied to tension the knot. The suture diameter was measured. Then the knot diameter was measured in two planes using an analogue micrometer. The internal diameter of a Mitek knot-pusher was measured. The mean maximum diameter for each knot was respectively PDS, 2.061 +/- 0.13 mm; Panacryl, 1.907 +/- 0.14 mm; Ethibond, 1.717 +/- 0.16 mm and Fibrewire, 1.654 +/- 0.14 mm. There were significant differences in size between knots tied with different materials except between Ethibond and Fibrewire where the difference was not significant. For each set of knots the smallest maximum knot diameter observed was identified. This was respectively PDS, 1.92 mm; Ethibond, 1.476 mm; Fibrewire, 1.488 mm and Panacryl, 1.715 mm. The internal diameter of a Mitek knot-pusher was found to be 1.95 mm. The current Mitek knot-pusher appears to be well suited to one PDS and two Panacryl. It appears less ideal for two Ethibond and two Fibrewire. One knot-pusher does not fit all and we suggest that different knot-pushers be used for different suture materials.

Delayed repair of the quadriceps using the Mitek anchor system: a case report and review of the literature

Extensor mechanism disruptions are relatively uncommon knee injuries. Within this group, delayed treatment is an infrequent but difficult clinical situation. Fibrous degeneration, muscle contraction and subsequent hiatus present a challenge to the orthopaedic surgeon. We present an unusual case of a successful delayed repair using the Mitek anchors system (Mitek Products Inc., a division of Ethicon Inc., Westwood, Massachusetts).