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.

Giant cell myositis associated with metastatic thymoma and granulomatous hypercalcaemia.

Giant cell myositis (GCM) is a rare inflammatory myopathy associated with myasthenia gravis and thymoma. Here, we report on a woman in her late 50s with a history of myasthenia gravis, systemic lupus erythematosus and stage IV thymoma with pleural metastases, who presented with proximal weakness, neuromuscular respiratory failure and hypercalcaemia. She was diagnosed with GCM via muscle biopsy and screened for myocarditis but showed no evidence of myocardial involvement. Her hypercalcaemia was consistent with a granulomatous process, likely driven by her GCM. Her strength gradually improved, and her hypercalcaemia did not recur after treatment with high dose steroids, intravenous immune globulin and plasma exchange. Her course was complicated by several opportunistic infections in the setting of her immunosuppression. Despite the high morbidity associated with GCM, she demonstrated clinical improvement after initiating immunosuppressive therapy and continues to be managed in the outpatient setting.

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.

Case of thymoma-associated cutaneous graft-versus-host disease-like disease successfully improved by narrowband ultraviolet B phototherapy.

Thymoma-associated graft-versus-host disease (GVHD)-like disease is a rare paraneoplastic disease seen in patients with thymoma. Here, we describe the first case of thymoma-associated GVHD-like disease localized to the skin that was successfully improved by a combination of systemic corticosteroids and whole-body narrowband ultraviolet (UV)-B phototherapy. The patient had developed toxic epidermal necrolysis-like erosive skin lesions over the whole body. Although systemic corticosteroids were effective up to a point, we were unable to begin the steroid taper. The addition of systemic narrowband UV-B phototherapy improved the skin manifestation of this disease, allowing corticosteroids to be reduced to a third of the original dose. Histopathologically, it was confirmed that the proportion of Foxp3-positive lymphocytes in the skin increased after narrowband UV-B irradiation. We propose that whole-body narrowband UV-B phototherapy is a good therapeutic option for the skin manifestation of thymoma-associated GVHD-like disease.

Clinical and immunological predictors of prognosis for Japanese patients with thymoma-associated myasthenia gravis.

There are no immunological markers to predict the prognosis of thymoma-associated myasthenia gravis (MG). Clinical and immunological factors associated with thymoma recurrence or MG relapse were examined by logistic analyses in 56 Japanese patients with thymoma-associated MG. Patients with anti-Kv1.4 antibodies showed higher frequencies of thymoma recurrence and MG relapse compared to those without. Anti-Kv1.4 antibody, Masaoka stage 4, World Health Organization type B3, and adjuvant radiotherapy were associated with thymoma recurrence. Multivariate analyses showed that anti-Kv1.4 antibody was the only independent factor associated with MG relapse. Anti-Kv1.4 antibody is a useful predictor of the prognosis of thymoma-associated MG.

Antibodies to CRMP3-4 associated with limbic encephalitis and thymoma.

We present a case with subacute limbic encephalitis (LE) and thymoma. Neither classical onconeural antibodies nor antibodies to voltage gated potassium channels (VGKC) were detected, but the serum was positive for anti-glutamic acid decarboxylase (GAD). The patient serum also stained synaptic boutons of pyramidal cells and nuclei of granule cells of rat hippocampus. The objective of the study was to identify new antibodies associated with LE. Screening a cDNA expression library identified collapsin response mediator protein 3 (CRMP3), a protein involved in neurite outgrowth. The serum also reacted with both CRMP3 and CRMP4 by Western blot. Similar binding pattern of hippocampal granule cells was obtained with the patient serum and rabbit anti-serum against CRMP1-4. The CRMP1-4 antibodies stained neuronal nuclei of a biopsy from the patient's temporal lobe, but CRMP1-4 expression in thymoma could only be detected by immunoblotting. Absorption studies with recombinant GAD failed to abolish the staining of the hippocampal granule cells. Our findings illustrate that CRMP3-4 antibodies can be associated with LE and thymoma. This has previously been associated with CRMP5.

[Relationship between thymectomy and syndrome differentiation-typing treatment of myasthenia gravis].

According to the theory of traditional Chinese medicine, 37 patients suffering from myasthenia gravis were Syndrome-differentiated into following types preoperationally: (1) Both Qi-Yin Deficiency of Kidney-Spleen, 21 cases. (2) Yang Deficiency of Kidney-Spleen, 15 cases. (3) Qi Deficiency of Spleen only, one case. Thymectomy were done in all cases. Among them, 19 cases had thymoma. The results showed the relationship between the types and the resectionability rate and post-operative crisis rate. On the first two types, they were 95.2% and 9.5%, 46.7% and 73.3% respectively. It was considered that Syndrome differentiation-typing in TCM in the myasthenia gravis patients would provide an positive and reliable index for predicting the resectionability and prognosis of the patient.

[Neuromuscular complications of D-penicillamine in rheumatoid arthritis]. / Complications neuromusculaires de la D. pénicillamine dans la polyarthrite rhumatoïde.

Between 1979 and 1990 we have seen 8 patients (7 females) with rheumatoid arthritis (RA) who developed a neuro-muscular involvement while on D-penicillamine (D.P.). Five of them had a drug-induced myasthenia. D.P. withdrawal led to a complete recovery in 1.5 to 5 months. Another patient presented with a myopathy which led to the diagnosis of Grave's disease. She was treated with D.P. for 4 months. D.P. was reintroduced and 5 months later a myasthenic syndrome developed. A thymoma was discovered 1 year later. In the last 2 patients D.P. induced polymyositis which, in one, was associated with features of systemic lupus erythematosus. In the other patient, the evolution was fatal in spite of D.P. withdrawal, high dose steroids and plasma exchanges. A literature survey has shown 150 D.P. induced myasthenia and 38 D.P. induced polymyositis cases.

Selective uptake of 75Se-selenomethionine by thymoma with pre red cell aplasia.

Red cell aplasia and an enlarging anterior mediastinal mass developed in a patient being followed for thyroid carcinoma. Differential diagnosis included thymoma and metastatic thyroid carcinoma. Preoperative scanning demonstrated significant uptake of 75Se-selenomethionine whereas 67Ga-galiium citrate failed to visualize the mass. Subsequent thoracotomy revealed a lymphocytic thymoma which was resected, resulting in reversal of the red cell aplasia. The use of 75Se-selenomethionine scanning maybe a useful adjunct in the preoperative evaluation of suspected thymomas.

B lymphocytes lacking surface IG in patients with immune deficiency: initiation of IG synthesis in culture in cells of a patient with thymoma.

A 64-year-old woman with a syndrome of thymoma, severe hypogammaglobulinemia, seemingly normal cell-mediated immunity and aplastic anemia, was found to have virtually no immunoglobulin- (Ig) bearing peripheral blood lymphocytes (PBL). However, 7.8 +/- 3.4% of the PBL were positive for another B-cell marker, the receptor for aggregated IgG, while the remaining cells bound sheep erythrocytes. Those cells which were aggregate-reactive appeared to be immature or incomplete B cells. Cultures of peripheral blood leukocytes from the patient in various serum-containing media were studied by 3 independent technics for the development of lymphocyte surface Ig and for Ig in the culture supernatants. In vitro the patient's cells were able to develop surface Ig in media supplemented with fetal calf serum (FCS) or normal serum; in media supplemented with autologous serum, the cells developed no surface Ig. During the cultures in FCS, human Ig determinants became detectable in the medium, and both medium and cell-surface Ig underwent a shift from mu determinants early in the culture period to gamma and alpha determinants later. The development of Ig on the cells was not inhibited by the presence of autologous serum if FCS was included in the medium. These data support the concept that a factor, missing from this patient's serum, is required at an early stage in the maturation of the B cell. A patient with X-linked agammaglobulinemia had a population of circulating lymphocytes with surface characteristics similar to the B cells of the thymoma case. In contrast, no Ig synthesis by this patient's cultured cells could be demonstrated, indicating a different level of block in the 2 cases despite their similarity at the level of the cell surface.