Case Report: Autoimmune Encephalitis Associated With Anti-glutamic Acid Decarboxylase Antibodies: A Pediatric Case Series

Successfully treated anti-GAD limbic encephalitis in a 15-year-old diabetic boy with intravenous immunoglobulin: case report

Introduction and importance

Limbic encephalitides (LE) have symptoms and signs of new-onset seizures accompanied by cognitive impairment and signal changes in the MRI of the limbic system in the brain. Numerous antibodies against the neurons and synapses have been detected so far. Of those, antiglutamic acid decarboxylase antibody (Anti-GAD Ab) impairs the gamma amino butyric acid, one of the primary mediators that naturally prevents abnormal neuronal activity causing seizure.

Case presentation

The authors have reported a case of anti-GAD Ab LE in a diabetic male adolescent who responded dramatically to intravenous immunoglobulin and reviewed all similar pediatric cases for 15 years now.

Clinical discussion

The symptoms in children suffering from anti-GAD LE in three categories, systemic, psychiatric, and neurological, are heterogeneous. The most common manifestations were seizures followed by altered mental status and behavioral changes, respectively. The two main clinical scenarios described in GAD65-mediated autoimmune epilepsy are (1) an acute/subacute onset of seizures alone or seizures (including new-onset refractory status epilepticus, NORSE) accompanied by some degrees of cognitive and psychiatric manifestations, including amnesia and mesiotemporal inflammatory involvement consistent with LE and (2) epilepsy without clinical or MRI evidence of active central nervous system inflammation.

Conclusion

Although rare, the neurologist should consider the potential role of anti-GAD ab-associated encephalitis in the presence of diabetes mellitus.

Co-existence of anti-glutamic acid decarboxylase-65 and anti-sry-like high-mobility group box receptor antibody-associated autoimmune encephalitis: A rare case report

Autoimmune encephalitis (AE) has been increasingly recognized in children. An 11-year-old Saudi boy presented with prodromal symptoms of fever and headache followed by behavioral changes, cognitive impairment, and focal seizures. Cerebrospinal fluid (CSF) analysis showed pleocytosis. Brain magnetic resonance imaging showed T2/fluid-attenuated inversion recovery hyperintensities involving the temporal, parietal and frontal lobes. Electroencephalography revealed diffuse encephalopathy and electrographic seizures. AE was suspected; intravenous methylprednisolone and immunoglobulin were administered. Autoantibodies against glutamic acid decarboxylase-65 were detected in his serum and CSF and against Sry-like high- mobility group box 1 in his serum only. The patient was diagnosed with seropositive AE and favorably responded to intensive immunosuppressive therapy.

A case report of anti-GAD65 antibody-positive autoimmune encephalitis in children associated with autoimmune polyendocrine syndrome type-II and literature review

Background

Glutamic acid decarboxylase (GAD) is the rate-limiting enzyme for the synthesis of gamma-aminobutyric acid (GABA), the major inhibitory neurotransmitter in the central nervous system. Antibodies against glutamic acid decarboxylase (GAD) are associated with various neurologic conditions described in patients, including stiff person syndrome, cerebellar ataxia, refractory epilepsy, and limbic and extra limbic encephalitis. While there are few case reports and research on anti-GAD65 antibody-associated encephalitis in adults, such cases are extremely rare in pediatric cases.

Methods

For the first time, we report a case of anti-GAD65-positive autoimmune encephalitis associated with autoimmune polyendocrine syndrome (APS) type II. We reviewed previously published pediatric cases of anti-GAD65 autoimmune encephalitis to discuss their clinical features, laboratory tests, imaging findings, EEG patterns, and prognosis.

Case presentation

An 8-year-old, male child presented to the outpatient department after experiencing generalized convulsions for twenty days. The child was admitted for epilepsy and had received oral sodium valproate (500 mg/day) in another center, where investigations such as USG abdomen and MRI brain revealed no abnormalities, however, had abnormal EEG with diffuse mixed activity in the left anterior middle prefrontal temporal region. On the follow-up day, a repeat blood test showed a very low serum drug concentration of sodium valproate hence the dose was increased to 750 mg/day. Then, the child experienced adverse effects including increased sleep, thirst, and poor appetite, prompting the parents to discontinue the medication. A repeat MRI showed increased signals on FLAIR sequences in the right hippocampus hence admitted for further management. The child's past history included a diagnosis of hypothyroidism at the age of 4, and receiving levothyroxine 75 mcg once daily. His parents are healthy with no history of any similar neurological, autoimmune, or genetic diseases, but his uncle had a history of epilepsy. At presentation, he had uncontrolled blood glucose levels with elevated HbA1c levels. Additionally, the serum and CSF autoantibodies were positive against the anti-GAD65 antibody with the titer of 1:100 and 1:32 respectively. The patient was managed with a mixed type of insulin regimen and received first-line immunotherapy (intravenous immunoglobulin, IVIG) for five consecutive days, followed by oral prednisone and sodium valproate as an antiepileptic drug. Upon achieving a favorable clinical outcome, the patient was discharged with oral medications.

Results

Among the 15 pediatric patients reported in this literature, nine presented with limbic encephalitis (LE), three with extralimbic encephalitis (ELE), and three with a combination of limbic and extralimbic encephalitis. Most of these cases exhibited T2-W FLAIR hyperintensities primarily localized to the temporal lobes in the early phase, progressing to hippocampal sclerosis/atrophy in the later phase on MRI. EEG commonly showed slow or spike waves on frontotemporal lobes with epileptic discharges. Prognostic factors varied among patients, with some experiencing persistent refractory seizures, type-1 diabetes mellitus (T1DM), persistent memory impairment, persistent disability requiring full assistance, and, in severe cases, death.

Conclusion

Our findings suggest that anti-GAD65 antibody-positive autoimmune encephalitis patients may concurrently present with other APS. Our unique case presented with multiple endocrine syndromes and represents the first reported occurrence in children. Early diagnosis and timely initiation of immunotherapy are crucial for improving clinical symptoms and reducing the likelihood of relapses or permanent disabilities. Therefore, emphasis should be placed on prompt diagnosis and appropriate treatment implementation to achieve better patient outcomes.

Case report: Successful autologous hematopoietic stem cell transplantation in a patient with GAD antibody-spectrum disorder with rapidly progressive dementia

The prevalence of neurological syndromes associated with antibodies to glutamic acid decarboxylase is increasing. While cognitive impairment is a common feature of this condition, it seldom emerges as the primary symptom. In this study, we discuss a case of refractory dementia associated with the glutamic acid decarboxylase spectrum disorder. Interestingly, this case showed a favorable outcome following autologous hematopoietic stem cell transplantation. We also provide an in-depth review of the current literature on the use of this therapeutic approach for the treatment of this disease.

Determination of Clinical, Electrophysiological, and Radiological Characteristics of Pediatric Autoimmune Encephalopathy

Autoimmune encephalopathy (AE) is a group of diseases with subacute onset, that represents a wide clinical spectrum, manifested by complex neuropsychiatric symptoms and signs. In this study, the data of 27 patients diagnosed and followed up in our clinic with the diagnosis of AE between 2011 and 2021 were evaluated retrospectively. Out of 27 patients, 6 were definite seropositive AE, 2 of them met the diagnostic criteria for limbic encephalitis, and the remaining 19 were probable AE. Nowadays, we see AEs with increasing frequency. While there is a generally established approach in the diagnosis and treatment of seropositive patients, there are still hesitations and diagnostic difficulties in seronegative AEs. In this study, clinical, radiological, and prognostic features of definite and probable AE patients diagnosed in a tertiary pediatric neurology clinic were documented. It is thought that pediatric neurologists have an important responsibility to increase awareness about AE in pediatricians. In the future, it is predicted that AE will be diagnosed more frequently with new antibodies and one has to differentiate it from viral encephalitis and neuropsychiatric syndromes and diseases.

The clinical relevance of anti-glutamic acid decarboxylase antibodies in children with encephalitis/encephalopathy

Anti-glutamic acid decarboxylase (anti-GAD) antibodies are associated with different types of syndromes. However, few studies have investigated the correlation between anti-GAD antibody titers with clinical severity and outcomes in children with encephalitis/encephalopathy. In this single-center retrospective cohort study, we consecutively enrolled hospitalized children who had encephalitis and/or encephalopathy with positive anti-GAD antibodies in serum and/or cerebrospinal fluid (CSF) from February 2010 to October 2021. Thirty-seven patients were included and divided into high-titer and low-titer groups. The patients with high anti-GAD antibody titers were associated with initial symptoms of language difficulty and ataxia. The level of titers was not associated with severity or outcomes. Anti-GAD antibody titers decreased after immunotherapy, however, the clinical response to immunotherapy was variable. A transient elevation in anti-GAD antibody titers during immunotherapy was noted. Further studies are warranted to investigate the role of anti-GAD antibodies in the pathogenesis and immune mechanisms of encephalitis/encephalopathy.

Autoimmune meningoencephalitis associated with anti-glutamic acid decarboxylase antibody following COVID-19 infection: A case report

Anti-glutamic acid decarboxylase (Anti-GAD) are associated with various neurologic condition; but no meningitis has been reported with it, so far. Evidence demonstrates the associated of autoimmune meningoencephalitis with COVID-19 infection. Here, we report a 44-year-old female with progressive loss of consciousness with anti-GAD65 meningoencephalitis 1 month after COVID-19 infection.