Systematic Review of the Clinical Characteristics and Management of Isaac Syndrome.

OBJECTIVES: Isaac syndrome (IS) is a condition characterized by peripheral nerve hyperexcitability caused by voltage-gated potassium channel (VGKC)-complex antibodies. Muscle twitching, stiffness, hypertrophy, and dysautonomic characteristics, such as hyperhidrosis, are common manifestations. The syndrome can be autoimmune or paraneoplastic, with thymoma being a common cause of paraneoplastic IS. Furthermore, this condition could be handed down from one generation to another. However, there is limited information regarding outcomes, relapses, associated syndromes, associated malignancies (other than thymoma), and treatment options. Despite its rarity, there remains a need for effective management strategies for patients with IS. To address this gap, we conducted a systematic review to summarize the most common and effective treatments of IS in immunomodulatory agents and symptomatic medications, as well as to describe outcomes, relapses, and associated malignancies. Altogether, this review serves to guide clinical practice recommendations for IS and highlight areas for further research. METHODS: We used the Preferred Reporting Items for Systematic Reviews and Meta-Analyses protocol to conduct a systematic review of cases reposted through the PubMed and Google Scholar databases. The terms "Isaac Syndrome" and "Acquired Neuromyotonia" were used. The Joanna Briggs Institute's critical appraisal tool was used to evaluate the quality of the included studies. RESULTS: We identified 61 case reports and 4 case series, comprising a total of 70 patients with IS (mean age at onset: 42.5 ± 18 years, and 69% were males). Fourteen cases reported relapses. Thymoma was the most common malignancy associated with IS, followed by lymphoma. Among various serum antibodies, voltage-gated potassium channel-complex antibodies were the most reported antibodies elevated in IS (reported in 38 patients and elevated in 21 patients [55.2%]), followed by acetylcholine ganglionic receptor antibodies, which were reported in 30% of patients (n = 21) and were elevated in 5 cases. The most common electromyography findings were myokymic discharges (n = 22), followed by fasciculations (n = 21) and neuromyotonia (n = 19). For treatment, combining anticonvulsants such as carbamazepine with immunotherapy therapy showed the best results in controlling the symptoms. Among immunotherapy therapies, the combination of plasma exchange plus intravenous high-dose steroids achieved the best results in the acute treatment of IS ([n = 6], with improvement noted in 83.3% [n = 5] of cases). Among the symptomatic treatments with anticonvulsants, carbamazepine was the most efficacious anticonvulsant in treatment of IS, with an average effective dosing of 480 mg/day (carbamazepine was used in 32.3% of acute treatment strategies [n = 23], with improvement noted in 73.9% [n = 17] of cases). CONCLUSIONS: IS a rare neuromuscular syndrome that tends to affect middle-aged men. These patients should be screened for thymoma and other malignancies such as lymphomas. The management of IS symptoms can be challenging, but based on our review, the combination of multiple immunosuppressives such as IV steroids and plasmapheresis with anticonvulsants such as carbamazepine seems to achieve the best results.

Isaacs' syndrome as the initial presentation of malignant thymoma and associated with double-positive voltage-gated potassium channel complex antibodies, a case report.

BACKGROUND: Isaacs' syndrome is a peripheral nerve hyperexcitability (PNH) syndrome due to peripheral motor nerve instability. Acquired Isaacs' syndrome is recognized as a paraneoplastic autoimmune disease with possible pathogenic voltage-gated potassium channel (VGKC) complex antibodies. However, the longitudinal correlation between clinical symptoms, VGKC antibodies level, and drug response is still unclear. CASE PRESENTATION: A 45-year-old man had progressive four limbs soreness, muscle twitching, cramps, and pain 4 months before admission. Electromyography (EMG) studies showed myokymic discharges, neuromyotonia, and an incremental response in the high-rate (50 Hz) repetitive nerve stimulation (RNS) test. Isaacs' syndrome was diagnosed based on clinical presentations and EMG reports. Serum studies showed positive VGKC complex antibodies, including leucine-rich glioma-inactivated 1 (LGI1) and contactin-associated protein-like 2 (CASPR2) antibodies. The acetylcholine receptor antibody was negative. Whole-body computed tomography (CT) and positron emission tomography revealed a mediastinal tumor with the great vessels encasement, right pleura, and diaphragm seeding. Biopsy confirmed a World Health Organization type B2 thymoma, with Masaoka stage IVa. His symptoms gradually improved and both LGI1 and CASPR2 antibodies titer became undetectable after concurrent chemoradiotherapy (CCRT) and high dose steroid treatment. However, his Isaacs' syndrome recurred after the steroid was reduced 5 months later. Follow-up chest CT showed probable thymoma progression. LGI1 antibody turned positive again while CASPR2 antibody remained undetectable. CONCLUSIONS: Our patient demonstrates that Isaacs' syndrome could be the initial and only neuromuscular manifestation of malignant thymoma. His Isaacs' syndrome is correlated well with the LGI1 antibody level. With an unresectable thymoma, long-term immunosuppressant therapy may be necessary for the management of Isaacs' syndrome in addition to CCRT for thymoma.

A "coughed up" tissue diagnosed as type A thymoma in an 80-year-old man: A case report.

RATIONALE: Thymoma is the most common primary tumor in the anterior mediastinum. All major subtypes of thymoma can be clinically aggressive. However, type A thymoma is usually benign and rarely invasive, let alone invasive to the trachea. There are no published reports of thymoma diagnosed in a "coughed up' tissue". Here, we report an 80-year-old man who coughed up a piece of tissue which was histopathologically diagnosed as type A thymoma. PATIENT CONCERNS: An 80-year-old man who had a history of thymoma for 8 years was admitted in our hospital with his severe cough and dyspnea and his "coughed up" something. He felt much better after coughing up the piece of tissue. He saved the tissue and sent it to the pathology department. DIAGNOSES: The clinical diagnosis was lung cancer. But the final pathological diagnosis was type A thymoma. INTERVENTIONS: The patient refused to get chemotherapy, or surgery, and only would like to get the traditional Chinese medicine. OUTCOMES: The patient is stable for 19 months after he coughed up some of the tumor tissue. LESSONS: The type A thymoma could be slowly aggressive. If left untreated, it would also invade into the trachea. When treat a patient with history of even a benign tumor, we should always bear the rare possibility in mind to avoid misdiagnosis. For an elderly patient, a "wait and see" policy may be acceptable.

ACTH-producing thymic neuroendocrine tumor initially presenting as psychosis: A case report and literature review.

A 32-year-old woman was referred to our hospital because of severe psychosis and was found to have an ectopic ACTH-producing thymic neuroendocrine tumor. Laboratory data revealed an elevated serum cortisol and plasma ACTH level, hypokalemia, and metabolic alkalosis. Chest computed tomography (CT) revealed an anterior mediastinal mass and multiple pulmonary nodules. As the patient was unable to communicate because of her consciousness disturbance, she was managed with artificial ventilation and deep sedation. Metyrapone and potassium supplementation were administered, and steroid psychosis gradually improved. Thoracic surgery was performed and the histopathological diagnosis was thymic neuroendocrine tumor with positive anti-ACTH immunohistochemical staining. Here we present details of the case and review the literature.

Verification of the diagnostic strategy for anterior mediastinal tumors.

BACKGROUND: For thymic epithelial tumors (TETs), the National Comprehensive Cancer Network guideline has suggested that complete excision of the tumor should be performed without a preoperative biopsy when resectable. However, little evidence has been provided to support this strategy. The purpose of this study was to review our diagnostic process and to evaluate the validity of radical resection of anterior mediastinal masses (AMMs) without pathological confirmation. METHODS: A total of 254 patients underwent surgical resection for AMMs between 2004 and 2015. This study included 181 patients with likely TETs according to clinical features, serum levels of tumor markers and autoimmune-antibodies, and radiological findings. In addition, AMMs likely TETs were classified into resectable or unresectable tumors. We retrospectively reviewed the diagnostic process of those patients and validated surgical resection of AMMs without a definitive diagnosis. RESULTS: Among 254 patients, 181 were suspected of having a TET based on the serum levels of tumor markers and autoimmune-antibodies and the radiological findings. Of them, 157 patients were deemed resectable and underwent surgical resection without histological confirmation, and 144 (92%) were diagnosed with TETs in the final pathological examinations. In 13 patients with non-TETs, the tumors were difficult to differentiate from TETs by imaging and clinical findings alone. CONCLUSIONS: A total of 92% of patients suspected of having a TET and who underwent complete resection without pathological confirmation were accurately diagnosed and properly treated. Surgical resection without a definitive diagnosis was feasible in patients suspected of having a TET when they were considered resectable.

Cytoreductive Pleurectomy and Intrathoracic Chemohyperthermia for Pleural Relapse of Thymomas.

Several surgical procedures, from debulking to extrapleural pneumonectomy, may be applied for stage IVa Masaoka thymomas, but their efficiency is still controversial. Case studies have favored R0 resection as the cornerstone of multimodal therapy for locoregional metastatic extension. This report describes a standardized procedure combining a cytoreductive surgical procedure and intrathoracic chemohyperthermia on a 46-year-old patient presenting with B2 thymoma and synchronous unilateral pleural metastasis.

Is thymomectomy equivalent to complete thymectomy in non-myasthenic patients with early-stage thymoma?

A best evidence topic in thoracic surgery was written according to a structured protocol. The question addressed is whether thymomectomy can be equivalent to thymectomy for non-myasthenic early-stage thymoma in terms of recurrence and survival. Ten papers were chosen to answer the question. The authors, journal, date and country of publication, patient group studied, study type, relevant outcomes and results of these papers were tabulated. All studies included in this analysis are retrospective; most of them are small and from single-institution experiences, and only 3 used propensity-matched analysis to minimize the patients' selection bias. The choice of performing thymectomy or thymomectomy was based on surgeons' preference rather than on a standardized surgical approach. Most papers found that thymectomy was equivalent to thymomectomy in terms of outcomes, but these results could be affected by the intergroup differences in terms of follow-up length, administration of induction or adjuvant therapy, histological subtypes distribution and tumour size. Conversely, the studies of the Japanese Association for Research on the Thymus and the Chinese Alliance for Research in Thymoma found a higher rate of local recurrence in the thymomectomy group than in the thymectomy group. The National Comprehensive Cancer Network, National Cancer Institute and International Thymic Malignancy Interest Group recommend complete thymectomy in non-myasthenic patients with early thymoma; therefore, the identified studies in this review are not strong enough to change this recommendation.

Precise Diagnosis and Treatment of Thymic Epithelial Tumors Based on Molecular Biomarkers.

Thymic epithelial tumors (TETs), including thymoma and thymic carcinoma, are rare malignant tumors. The mainstay of treatment patients with TET is surgical resection, and chemotherapy is necessary for patients with tumor invasion or metastasis who are unable to undergo complete radical excision. However, for those patients who are resistant to chemotherapy, targeted therapy has become the most popular tumor treatment program, as well as for thymic tumors. Many genes implicated in tumorigenesis and metastasis have also been reported to be therapeutic targets in thymic malignancies. A significant advance in TET treatment may derive from the identification of novel molecular biomarkers that can improve the diagnosis, prognosis, and treatment of tumors. We review a number of case reports and small clinical trials reporting that a few inhibitors, such as sorafenib and sunitinib, are effective in the treatment of thymoma. In this review, we describe the current potential drug targets and their roles in the development of thymic malignancy.

[Successful treatment with rituximab in a patient with primary thymic MALT lymphoma complicated with acquired von Willebrand syndrome and Sjögren syndrome].

A 53-year-old female developed epigastric discomfort and back pain in 2007. Diagnostic imaging studies demonstrated a soft tissue tumor with heterogeneous enhancement in the anterior mediastinum and multiple nodules in the right lung. She underwent expanded thymectomy with subtotal resection of the right lung. The pathological diagnosis was primary thymic mucosa-associated lymphoid tissue (MALT) lymphoma. The patient complained of ocular discomfort, oral dryness and continuous nasal bleeding in 2007. Detailed examination led to a diagnosis of Sjögren syndrome and acquired von Willebrand syndrome. Rituximab treatment for residual disease achieved not only a reduction of the lung MALT lymphoma but also clinical and hematological remission of both syndromes. This is, to our knowledge, the first reported case of primary thymic MALT lymphoma accompanied by Sjögren and acquired von Willebrand syndromes.

Hypothermia in VGKC antibody-associated limbic encephalitis.

Voltage-gated potassium channel antibody (VGKC-Ab)-associated limbic encephalitis (LE) is a recently described syndrome that broadens the spectrum of immunotherapy-responsive central nervous system disorders. Limbic encephalitis is typically characterised by a sub-acute onset of disorientation, amnesia and seizures, but the clinical spectrum is not yet fully defined and the syndrome could be under-diagnosed. We here describe the clinical profile of four patients with VGKC-Ab-associated LE who had intermittent, episodic hypothermia. One of the patients also described a prodrome of severe neuropathic pain preceding the development of limbic symptoms. Both of these novel symptoms responded well to immunosuppressive therapy, with concurrent amelioration of amnesia/seizures.