Spinocerebellar Ataxia-21 in a Turkish Child

Disorders of vesicular trafficking presenting with recurrent acute liver failure: NBAS, RINT1, and SCYL1 deficiency

Among genetic disorders of vesicular trafficking, there are three causing recurrent acute liver failure (RALF): NBAS, RINT1, and SCYL1-associated disease. These three disorders are characterized by liver crises triggered by febrile infections and account for a relevant proportion of RALF causes. While the frequency and severity of liver crises in NBAS and RINT1-associated disease decrease with age, patients with SCYL1 variants present with a progressive, cholestatic course. In all three diseases, there is a multisystemic, partially overlapping phenotype with variable expression, including liver, skeletal, and nervous systems, all organ systems with high secretory activity. There are no specific biomarkers for these diseases, and whole exome sequencing should be performed in patients with RALF of unknown etiology. NBAS, SCYL1, and RINT1 are involved in antegrade and retrograde vesicular trafficking. Pathomechanisms remain unclarified, but there is evidence of a decrease in concentration and stability of the protein primarily affected by the respective gene defect and its interaction partners, potentially causing impairment of vesicular transport. The impairment of protein secretion by compromised antegrade transport provides a possible explanation for different organ manifestations such as bone alteration due to lack of collagens or diabetes mellitus when insulin secretion is affected. Dysfunction of retrograde transport impairs membrane recycling and autophagy. The impairment of vesicular trafficking results in increased endoplasmic reticulum stress, which, in hepatocytes, can progress to hepatocytolysis. While there is no curative therapy, an early and consequent implementation of an emergency protocol seems crucial for optimal therapeutic management.

Acute Cerebellar Ataxia: A Rare Association of Hepatitis a Infection

Acute cerebellar ataxia (ACA) is a self-limited syndrome that is frequently post-infectious, most commonly following Varicella infection having an autoimmune mechanism. ACA is the commonest cause of childhood ataxia. We report a 14-year-old male who presented with acute onset wide-based gait and slurring of speech with dysdiadochokinesia, incoordination of voluntary movements, pendular knee jerk, and intentional tremors. He had worsening transaminitis and rising bilirubin during his hospital course and was subsequently found to be hepatitis A virus (HAV) immunoglobulin-M antibody positive. Thus, we report a case of ACA with HAV infection who developed jaundice after three weeks of onset of ataxia, a rarity that has not been reported so far in medical literature.

Recurrent Acute Liver Failure in a Bahraini Child With a Novel Mutation of Spinocerebellar Ataxia-21

Acute liver failure (ALF) in children is a rare life-threatening condition. ALF is caused by different etiologies. The most common causes are drug-induced liver injury, infections, and metabolic diseases. Other rare causes of ALF are genetic disorders including spinocerebellar ataxia-21 (SCAR21). Herein, we describe the first Bahraini child who was diagnosed with a novel homozygous mutation in the SCYL1 gene. He was admitted to the hospital twice by the age of two and five years due to acute hepatic failure triggered by a febrile illness. Drug-induced, infectious causes, and metabolic diseases were excluded. The liver function then gradually recovered. The patient had delayed gross motor development as he started to walk at 20 months of age. After the first episode of ALF, he had progressive difficulty in walking leading to frequent falls and ending with a complete inability to walk. A whole-exome sequencing (WES) test revealed that the patient has previously unreported autosomal recessive pathogenic non-sense variation c.895A>T (p.Lys299Ter) in exon 7 of the SCYL1 gene in a homozygous status. It is confirmed that the pathogenicity of this variant in the SCYL1 gene was associated with SCAR21 disease.