Stiff-person syndrome associated with multiple myeloma following autologous bone marrow transplantation

An update on malignant tumor-related stiff person syndrome spectrum disorders: clinical mechanism, treatment, and outcomes

Stiff person syndrome (SPS) is a rare central nervous system disorder associated with malignancies. In this review, we retrieved information from PubMed, up until August 2023, using various search terms and their combinations, including SPS, stiff person syndrome spectrum disorders (SPSSDs), paraneoplastic, cancer, and malignant tumor. Data from peer-reviewed journals printed in English were organized to explain the possible relationships between different carcinomas and SPSSD subtypes, as well as related autoantigens. From literature searching, it was revealed that breast cancer was the most prevalent carcinoma linked to SPSSDs, followed by lung cancer and lymphoma. Furthermore, classic SPS was the most common SPSSD subtype, followed by stiff limb syndrome and progressive encephalomyelitis with rigidity and myoclonus. GAD65 was the most common autoantigen in patients with cancer and SPSSDs, followed by amphiphysin and GlyR. Patients with cancer subtypes might have multiple SPSSD subtypes, and conversely, patients with SPSSD subtypes might have multiple carcinoma subtypes. The first aim of this review was to highlight the complex nature of the relationships among cancers, autoantigens, and SPSSDs as new information in this field continues to be generated globally. The adoption of an open-minded approach to updating information on new cancer subtypes, autoantigens, and SPSSDs is recommended to renew our database. The second aim of this review was to discuss SPS animal models, which will help us to understand the mechanisms underlying the pathogenesis of SPS. In future, elucidating the relationship among cancers, autoantigens, and SPSSDs is critical for the early prediction of cancer and discovery of new therapeutic modalities.

Stiff Person Spectrum Disorders-An Update and Outlook on Clinical, Pathophysiological and Treatment Perspectives

Stiff person spectrum disorders (SPSD) are paradigm autoimmune movement disorders characterized by stiffness, spasms and hyperekplexia. Though rare, SPSD represent a not-to-miss diagnosis because of the associated disease burden and treatment implications. After decades as an enigmatic orphan disease, major advances in our understanding of the evolving spectrum of diseases have been made along with the identification of multiple associated autoantibodies. However, the most important recent developments relate to the recognition of a wider affection, beyond the classic core motor symptoms, and to further insights into immunomodulatory and symptomatic therapies. In this review, we summarize the recent literature on the clinical and paraclinical spectrum, current pathophysiological understanding, as well as current and possibly future therapeutic strategies.

Severe anti-GAD antibody-associated encephalitis after stem cell transplantation

BACKGROUND

General features of anti-glutamic acid decarboxylase (GAD) antibody-associated limbic encephalitis are seizures, cognitive impairment, and imaging findings at the medial temporal lobes. We report a patient affected with remarkably severe anti-GAD antibody-positive encephalitis after hematopoietic stem cell transplantation (HSCT).

CASE REPORT

A 5-year-old girl received HSCT due to pineoblastoma. Thirteen months after HSCT, she showed seizure clustering and altered mental status. Her anti-GAD antibody level was high, 65,100 U/mL (reference range < 1.5 U/mL). Her disease was diagnosed as autoimmune encephalitis and she received intravenous immunoglobulin (IVIG) and methylprednisolone. After the therapy, she partially recovered. Encephalitis later relapsed, however, and she showed extremely high anti-GAD antibody, 27 months after HSCT. Although lesions were located in the temporal and occipital lobes by MRI at 5 days after the relapse, very severe whole brain encephalitis was revealed at 13 days after the relapse. Seizures and abnormal encephalogram were resistant to IVIG and methylprednisolone. After plasma exchange, these findings were resolved. MRI revealed diffuse cerebral atrophy, 57 months after the relapse. No relapse has occurred for the past 5 years with decreased anti-GAD antibody after starting bimonthly administration of IVIG.

CONCLUSION

This may be the first case of severe and recurrent anti-GAD antibody-associated autoimmune encephalitis after HSCT with specific MRI findings. No relapse has occurred since starting maintenance IVIG.

Paraneoplastic Neurological Syndromes and Glutamic Acid Decarboxylase Antibodies

IMPORTANCE

Little is known of glutamic acid decarboxylase antibodies (GAD-abs) in the paraneoplastic context. Clinical recognition of such cases will lead to prompt tumor diagnosis and appropriate treatment.

OBJECTIVE

To report the clinical and immunological features of patients with paraneoplastic neurological syndromes (PNS) and GAD-abs.

DESIGN, SETTING, AND PARTICIPANTS

Retrospective case series study and immunological investigations conducted in February 2014 in a center for autoimmune neurological disorders. Fifteen cases with GAD65-abs evaluated between 1995 and 2013 who fulfilled criteria of definite or possible PNS without concomitant onconeural antibodies were included in this study.

MAIN OUTCOMES AND MEASURES

Analysis of the clinical records of 15 patients and review of 19 previously reported cases. Indirect immunofluorescence with rat hippocampal neuronal cultures and cell-based assays with known neuronal cell-surface antigens were used. One hundred six patients with GAD65-abs and no cancer served as control individuals.

RESULTS

Eight of the 15 patients with cancer presented as classic paraneoplastic syndromes (5 limbic encephalitis, 1 paraneoplastic encephalomyelitis, 1 paraneoplastic cerebellar degeneration, and 1 opsoclonus-myoclonus syndrome). When compared with the 106 non-PNS cases, those with PNS were older (median age, 60 years vs 48 years; P = .03), more frequently male (60% vs 13%; P < .001), and had more often coexisting neuronal cell-surface antibodies, mainly against γ-aminobutyric acid receptors (53% vs 11%; P < .001). The tumors more frequently involved were lung (n = 6) and thymic neoplasms (n = 4). The risk for an underlying tumor was higher if the presentation was a classic PNS, if it was different from stiff-person syndrome or cerebellar ataxia (odds ratio, 10.5; 95% CI, 3.2-34.5), or if the patient had coexisting neuronal cell-surface antibodies (odds ratio, 6.8; 95% CI, 1.1-40.5). Compared with the current series, the 19 previously reported cases had more frequent stiff-person syndrome (74% vs 13%; P = .001) and better responses to treatment (79% vs 27%; P = .005). Predictors of improvement in the 34 patients (current and previously reported) included presentation with stiff-person syndrome and the presence of a thymic tumor.

CONCLUSIONS AND RELEVANCE

Patients with GAD-abs must be screened for an underlying cancer if they have clinical presentations different from those typically associated with this autoimmunity or develop classic PNS. The risk for cancer increases with age, male sex, and the presence of coexisting neuronal cell-surface antibodies.