Kelch-like protein 11 antibody-associated paraneoplastic neurological syndrome: A state-of-the-art review

Chronic lymphocytic inflammation with pontine perivascular enhancement responsive to steroids (CLIPPERS): contemporary advances and current controversies

Chronic lymphocytic inflammation with pontine perivascular enhancement responsive to steroids (CLIPPERS) is an inflammatory syndrome with characteristic clinical, radiological, and pathological features, and can be effectively treated with corticosteroid-based immunotherapies. The exact pathogenesis of CLIPPERS remains unclear, and specific diagnostic biomarkers are not available. According to the 2017 diagnostic criteria, probable CLIPPERS should be considered in middle-aged patients with subacute onset of pontocerebellar symptoms and typical punctuate and curvilinear gadolinium enhancement lesions ("salt-and-pepper" appearance) located in the hindbrain (especially pons) on magnetic resonance imaging. In addition, CLIPPERS-mimics, such as central nervous system (CNS) lymphoma, and several antibody-associated autoimmune CNS diseases (e.g., myelin oligodendrocyte glycoprotein antibody-associated disease, autoimmune glial fibrillary acidic protein astrocytopathy, and anti-N-methyl-D-aspartate receptor encephalitis), should be extensively excluded. The prerequisite for definite CLIPPERS is the perivascular T-cell-predominant inflammatory infiltration observed on pathological analysis. A biopsy is strongly suggested when clinical/radiological red flags are present. Most patients with CLIPPERS respond well to corticosteroids and have a good prognosis. Long-term low-dose corticosteroid maintenance therapy or corticosteroids coupled with immunosuppressants are recommended to prevent the recurrence of the syndrome. The potential progression of CLIPPERS to lymphoma has been suggested in some cases; therefore, at least 2-year clinical and radiological follow-up is essential. Here, we critically review the recent developments and provided an update on the clinical characteristics, diagnostic criteria, differential diagnoses, and therapeutic management of CLIPPERS. We also discuss the current controversies in this context that can be resolved in future research studies.

Anti-adenylate kinase 5 encephalitis: Clinical characteristics, diagnosis, and management of this rare entity

The spectrum and understanding of antibody-positive autoimmune encephalitis (AE) have expanded over the past few decades. In 2007, a rare subtype of AE known as anti-adenylate kinase 5 (AK5) encephalitis, was first reported. This disease is more common in elderly males, with limbic encephalitis as the core phenotype (characterized by subacute anterograde amnesia, sometimes with psychiatric symptoms, and rarely with seizures). Brain magnetic resonance imaging typically demonstrated initial temporal lobe T2/fluid-attenuated inversion recovery hyperintensities, and subsequent atrophy. No concomitant tumors have been found yet. AK5 antibody, targeting the intracellular antigen, is a biomarker for a non-paraneoplastic T-cell autoimmunity response, and can be detected in serum and cerebrospinal fluid using tissue-based and cell-based assays. Cytotoxic T-cell-mediating neuronal injury and loss play a pivotal role in the immunopathogenesis of anti-AK5 encephalitis. Patients mostly show poor response to immunotherapy and thus a poor prognosis in the long run. Herein, we review the literature and provide updated knowledge of this less-known entity, focusing on clinical characteristics, paraclinical findings, diagnosis process, and therapeutic approaches.

KLHL11 antibody-associated autoimmune encephalomyelitis in a middle-aged female patient: a case report and literature review

HEADINGS

Kelch-like protein 11antibody is a recently identified biomarker for paraneoplastic neurological syndromes associated with germ-cell tumors that was first described as an onconeural antibody causing autoimmune encephalitis associated with seminoma in 2019. Ataxia is the most prevalent presenting symptom, with other neurological symptoms including vertigo, double vision, hearing loss, tinnitus and dysarthria. Magnetic resonance imaging scans reveal that the lesions are mostly located in the cerebellum and brainstem, particularly in the pontine region, and may also exhibit cerebellar atrophy.

AIM OF THE STUDY

In this study, we report the clinical features of Kelch-like protein 11 antibody-associated paraneoplastic neurological syndrome.

MATERIALS AND METHODS

We present a middle-aged female patient who presented with vertigo, cognitive decline, ataxia and limb weakness. A cell-based assay (CBA) showed positive IgG Kelch-like protein 11 in both her serum and CSF, as well as positive oligoclonal bands in her CSF. She was diagnosed with KLHL11 antibody-associated autoimmune encephalomyelitis and received high-dose intravenous methylprednisolone pulse therapy.

RESULT AND CONCLUSIONS

Clinical outcomes suggest that patients with Kelch-like protein 11 antibody mostly have poor prognoses, excepting our case. We propose that early and appropriate treatments are critical for timely diagnosis and rapid improvement.

Primary mediastinal seminoma presenting with paraneoplastic anti-Hu encephalitis: a case report and literature review

Primary mediastinal seminomas are exceedingly rare tumors, often localized to the anterior mediastinum. They may present with numerous complications, including superior vena cava syndrome, chylothorax, and pericardial effusions. Less commonly, they may present with paraneoplastic encephalitis. In this report we describe a case of a 19-year-old male with no significant past medical history who presented with bilateral hearing loss, progressive neuropathy, and ataxia. Subsequently the patient was found to have mediastinal mass with a high-titer anti-Hu antibody. To our knowledge, only one other case of mediastinal seminoma presenting with anti-Hu antibodies has been described in the literature. In this report, we describe a rare case of mediastinal seminoma, describe treatment options, and discuss additional known cases presenting with paraneoplastic encephalitis.

Paraneoplastic Kelch-like protein 11 antibody-associated cerebellar and limbic encephalitis caused by metastatic “burned-out” seminoma – A scar(r)y phenomenon

INTRODUCTION

The diagnosis of paraneoplastic neurologic syndromes is challenging when the primary tumor masquerades as scar tissue (i.e. "burned-out").

METHODS

Case report.

RESULTS

A 45-year-old male patient presented with progressive cerebellar symptoms and hearing loss. Initial screening for malignancy and extensive testing of paraneoplastic and autoimmune neuronal antibodies gave negative results. Repeated whole-body FDG-PET CT revealed a single paraaortic lymphadenopathy, metastasis of a regressed testicular seminoma. Anti-Kelch-like protein-11 (KLHL11) encephalitis was finally diagnosed.

CONCLUSION

Our case highlights the importance of continued efforts to find an often burned-out testicular cancer in patients with a highly unique clinical presentation of KLHL11 encephalitis.

Anti-kelchlike protein 11 antibody-associated encephalitis: Two case reports and review of the literature

BACKGROUND AND PURPOSE

Kelchlike protein 11 antibodies (KLHL11-IgGs) were first described in 2019 as a marker of paraneoplastic neurological syndromes (PNSs). They have mostly been associated with testicular germ cell tumors (tGCTs).

METHODS

Two patients with KLHL11-IgG encephalitis are reported, and the literature is comprehensively reviewed.

RESULTS

Patient 1 had been in remission from a tGCT 10 years prior. He developed episodic vertigo and diplopia progressing over a few days. Treatment with corticosteroids (CSs) was started a few days after symptom onset. Patient 2 had transient diplopia, which resolved spontaneously. Visual problems persisted for 7 months, when he additionally developed a progressive cerebellar syndrome. One year after onset, CS treatment was started. Initial magnetic resonance imaging was unremarkable in both patients, but analysis of cerebrospinal fluid (CSF) revealed chronic inflammation. KLHL11-IgG was positive in both patients (Patient 1 only in CSF, Patient 2 in serum). Neoplastic screening has so far not revealed any signs of active underlying malignancy. We found 15 publications of 112 patients in total with KLHL11-IgG encephalitis. Most patients (n = 82) had a cerebellar syndrome with or without signs of rhombencephalitis. The most common symptoms were ataxia (n = 82) and vertigo (n = 47), followed by oculomotor disturbances (n = 35) and hearing disorders (n = 31). Eighty of 84 patients had a GCT as an underlying tumor.

CONCLUSIONS

Our cases demonstrate classical symptoms of KLHL11-IgG encephalitis. Early diagnosis and therapy are imperative. As with other PNSs, clinical awareness is needed and further studies are required especially in regard to therapeutic management.