Revisiting anti-Hu paraneoplastic autoimmunity: phenotypic characterization and cancer diagnosis

Central nervous system adverse events of immune checkpoint inhibitors

PURPOSE OF REVIEW

Immune checkpoint inhibitors (ICI) may trigger immune-related adverse events which rarely affect the central nervous system (CNS-irAEs). Over the past few years, cumulative data have led to the characterization of well defined syndromes with distinct cancer and antibody associations as well as different outcomes.

RECENT FINDINGS

The most frequent CNS-irAE is encephalitis, which includes three main groups: meningoencephalitis, a nonfocal syndrome usually responsive to corticosteroids; limbic encephalitis, associated with high-risk paraneoplastic neurological syndromes (PNS) antibodies (e.g. anti-Hu, anti-Ma2) and neuroendocrine cancers, characterized by poor treatment response and outcomes; and cerebellar ataxia, with variable outcomes (worse when high-risk PNS antibodies are detected). Additionally, a diffuse encephalopathy without inflammatory findings, with poor response to corticosteroids and high mortality has been described. The spectrum of CNS-irAEs also includes meningitis, myelitis, and rarer presentations. A subset of CNS-irAEs (i.e. limbic encephalitis and/or rapidly progressive cerebellar ataxia) is undistinguishable from ICI-naïve PNS.

SUMMARY

The clinical and outcomes diversity of CNS-irAEs suggests different pathogenic mechanisms, which need to be understood to establish more effective and specific treatment modalities. It is crucial to identify biomarkers able to predict which patients will experience severe CNS-irAEs, to anticipate their diagnosis, and to predict long-term outcomes.

Dysautonomia in anti-Hu paraneoplastic neurological syndromes

BACKGROUND AND OBJECTIVES

Dysautonomia has been associated with paraneoplastic neurological syndrome (PNS)-related mortality in anti-Hu PNS, but its frequency and spectrum remain ill-defined. We describe anti-Hu patients with dysautonomia, estimate its frequency, and compare them to patients without dysautonomia.

METHODS

Patients with anti-Hu antibodies diagnosed in the study centre (1990-2022) were retrospectively reviewed; those with autonomic signs and symptoms were identified.

RESULTS

Among 477 anti-Hu patients, 126 (26%) had dysautonomia (the only PNS manifestation in 7/126, 6%); gastrointestinal (82/126, 65%), cardiovascular (64/126, 51%), urogenital (24/126, 19%), pupillomotor/secretomotor (each, 11/126, 9%), and central hypoventilation (10/126, 8%). Patients with isolated CNS involvement less frequently had gastrointestinal dysautonomia than those with peripheral (alone or combined with CNS) involvement (7/23, 30% vs. 31/44, 70% vs. 37/52, 71%; P = 0.002); while more frequently central hypoventilation (7/23, 30% vs. 1/44, 2.3% vs. 2/52, 4%; P < 0.001) and/or cardiovascular alterations (18/23, 78% vs. 20/44, 45% vs. 26/52, 50%; P = 0.055). Median [95% CI] overall survival was not significantly different between patients with (37 [17; 91] months) or without dysautonomia (28 [22; 39] months; P = 0.78). Cardiovascular dysautonomia (HR: 1.57, 95% CI [1.05; 2.36]; P = 0.030) and central hypoventilation (HR: 3.51, 95% CI [1.54; 8.01]; P = 0.003) were associated with a higher risk of death, and secretomotor dysautonomia a lower risk (HR: 0.28, 95% CI [0.09; 0.89]; P = 0.032). Patients with cardiovascular dysautonomia dying ≤ 1 year from clinical onset had severe CNS (21/27, 78%), frequently brainstem (13/27, 48%), involvement.

DISCUSSION

Anti-Hu PNS dysautonomia is rarely isolated, frequently gastrointestinal, cardiovascular and urogenital. CNS dysfunction, particularly brainstem, associates with lethal cardiovascular alterations and central hypoventilation, while peripheral involvement preferentially associates with gastrointestinal or secretomotor dysautonomia, being the latest more indolent.

Interest of rare autoantibodies in autoimmune encephalitis and paraneoplastic neurological syndromes: the utility (or futility) of rare antibody discovery

PURPOSE OF REVIEW

The increasing recognition and diagnosis of autoimmune encephalitis (AE) and paraneoplastic neurological syndromes (PNS) is partly due to neural autoantibody testing and discovery. The past two decades witnessed an exponential growth in the number of identified neural antibodies. This review aims to summarize recent rare antibody discoveries in the context of central nervous system (CNS) autoimmunity and evaluate the ongoing debate about their utility.

RECENT FINDINGS

In the last 5 years alone 15 novel neural autoantibody specificities were identified. These include rare neural antibody biomarkers of autoimmune encephalitis, cerebellar ataxia or other movement disorders, including multifocal presentations.

SUMMARY

Although the clinical applications of these rare antibody discoveries may be limited by the low number of positive cases, they still provide important diagnostic, prognostic, and therapeutic insights.

Predicting disability and mortality in CV2/CRMP5-IgG associated paraneoplastic neurologic disorders

BACKGROUND

We aimed to investigate the prognostic factors associated with clinical outcomes in CV2/Collapsin response-mediator protein 5 (CRMP5)-IgG paraneoplastic neurologic disorders (PND).

METHODS

This is a retrospective study of patients with CV2/CRMP5-IgG PND evaluated between 2002-2022. We examined the association of clinical variables (including age, clinical phenotype [autoimmune encephalopathy, myelopathy, polyneuropathy/radiculopathy, MG, cerebellar ataxia, chorea, optic neuropathy], cancer) with three clinical outcomes (wheelchair dependence, modified Rankin Scale [mRS], mortality) using univariate logistic regression and Cox proportional hazards modeling. Kaplan-Meier estimates were used to determine the probability of survival.

RESULTS

Twenty-seven patients (56% female) with CV2/CRMP5-IgG PND were identified with a median follow-up of 54 months (IQR = 11-102). An underlying tumor was identified in 15 patients (56%) including small cell lung cancer (SCLC) (8, [53%]), thymoma (4, [27%]), and other histologies (3, [20%]). At last follow-up, 10 patients (37%) needed a wheelchair for mobility and this outcome was associated with myelopathy (HR = 7.57, 95% CI = 1.87-30.64, P = 0.005). Moderate-severe mRS = 3-5 was associated with CNS involvement (encephalopathy, myelopathy, or cerebellar ataxia) (OR = 7.00, 95% CI = 1.18-41.36, P = 0.032). The probability of survival 4 years after symptom onset was 66%. Among cancer subtypes, SCLC (HR = 18.18, 95% CI = 3.55-93.04, P < 0.001) was significantly associated with mortality, while thymoma was not.

INTERPRETATION

In this retrospective longitudinal study of CV2/CRMP5-IgG PND, patients with CNS involvement, particularly myelopathy, had higher probability of disability. SCLC was the main determinant of survival in this population.

Paraneoplastic Cerebellar Degeneration Associated with Breast Cancer: A Case Report and a Narrative Review

Paraneoplastic neurological syndromes (PNSs) are an uncommon complication of cancer, affecting nearby 1/10,000 subjects with a tumour. PNSs can involve all the central and peripheral nervous systems, the muscular system, and the neuromuscular junction, causing extremely variable symptomatology. The diagnosis of the paraneoplastic disease usually precedes the clinical manifestations of cancer, making an immediate recognition of the pathology crucial to obtain a better prognosis. PNSs are autoimmune diseases caused by the expression of common antigens by the tumour and the nervous system. Specific antibodies can help clinicians diagnose them, but unfortunately, they are not always detectable. Immunosuppressive therapy and the treatment of cancer are the cornerstones of therapy for PNSs. This paper reports a case of PNSs associated with breast tumours and focuses on the most common paraneoplastic neurological syndromes. We report a case of a young female with a clinical syndrome of the occurrence of rigidity in the right lower limb with postural instability with walking supported and diplopia, with a final diagnosis of paraneoplastic cerebellar degeneration and seronegative rigid human syndrome associated with infiltrating ductal carcinoma of the breast.

Autonomic nervous system involvement in autoimmune encephalitis and paraneoplastic neurological syndromes

In autoimmune neurological diseases, the autonomic nervous system can be the primary target of autoimmunity (e.g. autoimmune autonomic ganglionopathy), or, more frequently, be damaged together with other areas of the nervous system (e.g. Guillain-Barré syndrome). Patients with autoimmune encephalitis and paraneoplastic neurological syndromes (PNS) often develop dysautonomia; however, the frequency and spectrum of autonomic signs and symptoms remain ill defined except for those scenarios in which dysautonomia is a core feature of the disease. Such is the case of Lambert-Eaton myasthenic syndrome, Morvan syndrome or anti-NMDAR encephalitis; in the latter, patients with dysautonomia have been reported to carry a more severe disease and to retain higher disability than those without autonomic dysfunction. Likewise, the presence of autonomic involvement indicates a higher risk of death due to neurological cause in patients with anti-Hu PNS. However, in anti-Hu and other PNS, as well as in the context of immune checkpoint inhibitors' toxicities, the characterization of autonomic involvement is frequently overshadowed by the severity of other neurological symptoms and signs. When evaluated with tests specific for autonomic function, patients with autoimmune encephalitis or PNS usually show a more widespread autonomic involvement than clinically suggested, which may reflect a potential gap of care when it comes to diagnosing dysautonomia. This review aims to revise the autonomic involvement in patients with autoimmune encephalitis and PNS, using for that purpose an antibody-based approach. We also discuss and provide general recommendations for the evaluation and management of dysautonomia in these patients.