The Complex Genetic Landscape of Hereditary Ataxias in Turkey and Implications in Clinical Practice

BACKGROUND

The genetic and epidemiological features of hereditary ataxias have been reported in several populations; however, Turkey is still unexplored. Due to high consanguinity, recessive ataxias are more common in Turkey than in Western European populations.

OBJECTIVE

To identify the prevalence and genetic structure of hereditary ataxias in the Turkish population.

METHODS

Our cohort consisted of 1296 index cases and 324 affected family members. Polymerase chain reaction followed by Sanger sequencing or fragment analysis were performed to screen for the trinucleotide repeat expansions in families with a dominant inheritance pattern, as well as in sporadic cases. The expansion in the frataxin (FXN) gene was tested in all autosomal recessive cases and in sporadic cases with a compatible phenotype. Whole-exome sequencing was applied to 251 probands, selected based on the family history, age of onset, and phenotype.

RESULTS

Mutations in known ataxia genes were identified in 30% of 1296 probands. Friedreich's ataxia was found to be the most common recessive ataxia in Turkey, followed by autosomal recessive spastic ataxia of Charlevoix-Saguenay. Spinocerebellar ataxia types 2 and 1 were the most common dominant ataxias. Whole-exome sequencing was performed in 251 probands with an approximate diagnostic yield of 50%. Forty-eight novel variants were found in a plethora of genes, suggesting a high heterogeneity. Variants of unknown significance were discussed in light of clinical data.

CONCLUSION

With the large sample size recruited across the country, we consider that our results provide an accurate picture of the frequency of hereditary ataxias in Turkey. © 2021 International Parkinson and Movement Disorder Society.

Two Cases With Developing Neurologic Complications After Liver Transplant

The widespread use of immunosuppressive agents has significantly increased the rates of successful solid-organ and stem cell transplants, especially with liver and kidney. Cyclosporine and tacrolimus are most commonly used for this purpose. Although these agents have different mechanisms of action, both have various adverse effects, including nausea, vomiting, headache, hypertension, nephrotoxicity, and rarely epileptic seizures. In our first case, a patient presented with epileptic seizures and hemiparesis after a liver transplant, and posterior reversible encephalopathy syndrome related to cyclosporine toxicity was considered. Once cyclosporine levels in the blood decreased, the patient had both clinical and radiologic improvements. In our second case, a patient presented with delirium after a liver transplant. Again, when cyclosporine levels in the blood decreased, the patient showed improvement in clinical findings. Neurologic complications may develop after liver transplant, and these complications are encountered most frequently within the first postoperative month. Neurologic complications are multifactorial; insufficient graft function, intracranial bleeding, cerebral infarcts, infections, and immunosuppressive drug toxicity (tacrolimus and cyclosporine) may be considered among these factors. As shown in our presented cases, most neurologic complications can be successfully treated by correcting the underlying factor.

A case of hyperkinetic movement disorder associated with LGI1 antibodies

Encephalitis associated with leucine-rich glioma inactivated 1 (LGI1) antibodies is often encountered in elderly male patients and may infrequently present with isolated syndromes. A 6-year-old boy was admitted with acute onset severe oral and facial stereotypic and choreiform movements. On his neurologic examination, he had repetitive and rhythmic movements in orolingual muscles including tongue protrusion, limb chorea and minimal facial stereotypic movements. Anti-streptolysin O (ASO) titers were found severely elevated in several measurements. Well-characterized antibodies against ion channels and synapse proteins were negative whereas LGI1 antibody was positive in both serum and CSF. Marked clinical improvement was observed after immunotherapy. Here, we present the first pediatric case with LGI1 antibody associated hyperkinetic movement disorders and emphasize the importance of investigating neuronal autoantibodies in patients with isolated and treatment resistant movement disorders.