Leucoencephalopathy, transverse myelopathy, and peripheral neuropathy in association with glutamic acid decarboxylase-65 (GAD) antibodies in children with cancer

SPS: Understanding the complexity

INTRODUCTION

Stiff-person syndrome (SPS), first described in 1956 by Moersch and Woltman, is a progressive autoimmune disorder with core features of chronic fluctuating progressive truncal and limb rigidity and painful muscle spasms leading to gait difficulties, falls and an appearance that resembles tin soldiers. The syndrome is a rare, highly disabling disorder of the central nervous and frequently results in significant disability. Understanding of the etiology, clinical spectrum, diagnostic workup and therapeutic modalities for this painful and disabling disorder has vastly evolved over the past few years with more confidence in classifying and treating the patients. The purpose of this review is to increase the awareness, early detection, and treatment of this disabling disease.

METHOD

PubMed was searched, all date inclusive, using the following phrases: stiff person syndrome,anti-Glutamic acid decarboxylase (Anti-GAD) antibody syndrome, Progressive encephalomyelitis with rigidity and myoclonus (PERM), and Paraneoplastic Stiff Person syndrome. No filters or restrictions were used. A total of 888 articles were identified.

RESULTS

The results were narrowed to 190 citations after excluding non-English and duplicate reports. Clinical presentation, laboratory testing, treatment, and prognosis were categorized and summarized.

DISCUSSION

In this article we will discuss the epidemiology, presentation and classification. Explain the pathophysiology of SPS and the autoimmune mechanisms involved. Discuss the diagnostic approach and treatments available, as well as, the prognosis and outcome.

The role of the laboratory in the expanding field of neuroimmunology: Autoantibodies to neural targets

Accelerated identification of autoantibodies associated with previously idiopathic neurological disease has provided insights into disease mechanisms, enhanced understanding of neurological function, and opportunities for improved therapeutic interventions. The role of the laboratory in the expanding field of neuroimmunology is critical as specific autoantibody identification provides guidance to clinicians in diagnosis, prognosis, tumor search strategies, and therapeutic interventions. The number of specific autoantibodies identified continues to increase and newer testing strategies increase efficiencies in the laboratory and availability to clinicians. The need for broadly targeted efficient testing is underscored by the variability in clinical presentation and tumor associations attributable to a specific autoantibody, and conversely the various autoantibody specificities that can be the cause of a given clinical presentation. While many of the antineural antibodies were first recognized in the setting of neoplastic disease, idiopathic autoimmune neurological disease in the absence of underlying tumor is increasingly recognized. Appropriation of therapeutic modalities used to treat autoimmune disease to treat these autoantibody mediated neurological diseases has improved patient outcomes. Interaction between clinicians and laboratorians is critical to our understanding of these diseases and optimization of the clinical benefits of our increasing knowledge in neuroimmunology.

GAD65 neurological autoimmunity

The glutamic acid decarboxylase 65-kilodalton isoform (GAD65) antibody is a biomarker of autoimmune central nervous system (CNS) disorders and, more commonly, nonneurological autoimmune diseases. Type 1 diabetes, autoimmune thyroid disease, and pernicious anemia are the most frequent GAD65 autoimmune associations. One or more of these disorders coexists in approximately 70% of patients with GAD65 neurological autoimmunity. Neurological phenotypes have CNS localization and include limbic encephalitis, epilepsy, cerebellar ataxia, and stiff-person syndrome (SPS), among others. Classic SPS is a disorder on the spectrum of CNS hyperexcitability which also includes phenotypes that are either more restricted (stiff-limb syndrome) or more widespread (progressive encephalomyelitis with rigidity and myoclonus). GAD65 antibody is not highly predictive of a paraneoplastic cause for neurological disorders, but diverse cancer types have been occasionally reported. For all phenotypes, responses to immunotherapy are variable (approximately 50% improve). GAD65 autoimmunity is important to recognize for both coexisting nonneurological autoimmune associations and potential immunotherapy-response. Muscle Nerve 56: 15-27, 2017.

Dorsal column myelopathy after intrathecal chemotherapy for leukemia

Intrathecal chemotherapy with methotrexate, a folate antagonist, is widely used to treat central nervous system malignancies. The mechanisms underlying methotrexate-induced neurotoxicity are unclear but may be related to increased homocysteine levels. Intrathecal methotrexate-induced myelopathy mimicking subacute combined degeneration, with normal B12 levels, has been documented. We examined treatment and magnetic resonance imaging (MRI) characteristics of 13 patients with leukemia who received intrathecal methotrexate and developed urinary and bowel incontinence, ascending motor weakness, and sensory loss with dorsal column hyperintensity on MRI between 2000 and 2016. Cerebrospinal fluid evaluation was negative for leukemia in all patients and positive for elevated protein in 12 patients. Seven of eight patients with available data had reduced serum folate, increased serum homocysteine, or both, implicating methotrexate as the cause of neurotoxicity. Autopsy of one patient revealed loss of myelinated axons in the posterior columns. These findings suggest that methotrexate neurotoxicity may be mediated by folate antagonism. Awareness and a high index of suspicion of these characteristic clinical and radiographic features in patients who develop myelopathy after intrathecal methotrexate may help to avoid additional neurotoxic therapy in such patients.

Atypical neurologic presentations of new onset type 1 diabetes mellitus in pediatric age group: a report of five unusual cases and review of the literature

Type 1 diabetes mellitus (T1DM) is one of the most common chronic diseases in childhood and is caused by insulin deficiency resulting from the autoimmune destruction of insulin producing beta cells of the pancreas. Most children in the US with new onset T1DM present with the classic signs and symptoms of hyperglycemia and 30% with diabetic ketoacidosis (DKA). Neurologic manifestations are relatively rare and mostly include lethargy, decreased level of consciousness, and coma as a result of DKA. In this article, five cases of new onset T1DM with exceedingly rare or unreported neurologic manifestations in the pediatric age group are presented, along with a review of the literature.