Significant improvement in paraneoplastic neurological syndromes without identifiable anti-neural antibodies in patients with breast cancer after breast surgery.

Paraneoplastic neurological syndromes (PNS) are neurological disorders that occur in close association with tumors without direct metastasis or invasion of the tumors and in which anti-neural antibodies may be present. Cerebellar ataxia is a common form of PNS in patients with breast cancer. However, reports of symptom improvement with breast cancer treatment are more common in patients with positive anti-neural antibodies and are rarely seen in those with negative anti-neural antibodies. In addition, there have been few quantitative evaluations of symptom improvement. We report a case in which neurological symptoms significantly improved after surgical treatment for breast cancer. The patient was a 78-years-old woman with subacute progressive cerebellar ataxia. A subsequent diagnosis of breast cancer led to the diagnosis of "PNS probable". A comprehensive search for anti-neural antibodies was negative in all cases. The quantitative index of the Scale for the Assessment and Rating of Ataxia (SARA) score, a standard evaluation method for ataxia in spinocerebellar degeneration, improved after breast cancer surgery. This case may provide a rationale for treating breast cancer patients negative for anti-neural antibodies, with the possibility of improving neurological symptoms.

Nonspecific inflammatory pseudotumor of the maxillary and temporal fossa: a study of seven cases.

OBJECTIVE: Inflammatory pseudotumor (IPT) is a rare, locally aggressive, benign neoplasm of unknown etiology. Because of its aggressive clinical behavior and locally destructive or infiltrative features, it may be mistaken for a malignant tumor. Approximately 5%-44% of extrapulmonary IPT occur in the head and neck, primarily affecting the orbit. STUDY DESIGN: Between 2008 and 2021, our hospital received referrals for seven patients (three men and four women, aged 42-73 years) with pain, swelling, mass, and trismus. Computed tomography, magnetic resonance imaging, and biopsy were performed on all patients to diagnose IPT. RESULTS: Of the seven patients, four received low-dose prednisolone (PSL), one underwent surgery, and two were left untreated. The IPT disappeared in one of the two untreated cases, whereas it improved and later deteriorated in the other. The surgical patient had no recurrence. Low-dose PSL was effective in two patients; however, high-dose PSL and immunosuppressants were required in the remaining two cases owing to infiltration into each orbit or brain region. CONCLUSIONS: Low-dose PSL treatment was applicable in IPT cases affecting the maxillary to temporal fossa region, wherein symptoms did not improve without treatment. However, when low-dose PSL was ineffective, high-dose PSL and immunosuppressants were required.

Intracerebral transplantation of MRI-trackable autologous bone marrow stromal cells for patients with subacute ischemic stroke.

BACKGROUND: Ischemic stroke is one of the leading causes of death and neurological disability worldwide, and stem cell therapy is highly expected to reverse the sequelae. This phase 1/2, first-in-human study evaluated the safety, feasibility, and monitoring of an intracerebral-transplanted magnetic resonance imaging (MRI)-trackable autologous bone marrow stromal cell (HUNS001-01) for patients with subacute ischemic stroke. METHODS: The study included adults with severe disability due to ischemic stroke. HUNS001-01 cultured with human platelet lysates and labeled with superparamagnetic iron oxide was stereotactically transplanted into the peri-infarct area 47-64 days after ischemic stroke onset (dose: 2 or 5 × 107 cells). Neurological and radiographic evaluations were performed throughout 1 year after cell transplantation. The trial was registered at UMIN Clinical Trial Registry (number UMIN000026130). FINDINGS: All seven patients who met the inclusion criteria successfully achieved cell expansion, underwent intracerebral transplantation, and completed 1 year of follow-up. No product-related adverse events were observed. The median National Institutes of Health Stroke Scale and modified Rankin scale scores before transplantation were 13 and 4, which showed improvements of 1-8 and 0-2, respectively. Cell tracking proved that the engrafted cells migrated toward the infarction border area 1-6 months after transplantation, and the quantitative susceptibility mapping revealed that cell signals at the migrated area constantly increased throughout the follow-up period up to 34% of that of the initial transplanted site. CONCLUSIONS: Intracerebral transplantation of HUNS001-01 was safe and well tolerated. Cell tracking shed light on the therapeutic mechanisms of intracerebral transplantation. FUNDING: This work was supported by the Japan Agency for Medical Research and Development (AMED; JP17bk0104045 and JP20bk0104011).

A retrospective study of autoimmune cerebellar ataxia over a 20-year period in a single institution.

BACKGROUND: It is important to differentiate autoimmune cerebellar ataxia (ACA) from neurodegenerative CA, but this is sometimes difficult. We performed a retrospective study in a single institution in Japan over a 20-year period to reveal the clinical features of ACA. METHODS: Patients with CA as the primary neurological symptom were enrolled from those admitted to the Department of Neurology, Hokkaido University Hospital between April 2002 and March 2022. ACA was diagnosed retrospectively according to the following criteria: (1) CA being the predominant symptom; (2) identification of cancer within 2 years of onset; (3) improvement in cerebellar symptoms following immunotherapy; and (4) ruling out alternative causes of CA. Patients fulfilling criteria (1), (2), and (4) were classified as paraneoplastic cerebellar degeneration (PCD), while those fulfilling (1), (3), and (4) were classified as non-PCD and enrolled as patients with ACA. Neurodegenerative diseases, e.g., multiple system atrophy (MSA), were confirmed retrospectively based on generally used diagnostic criteria and enrolled. Furthermore, the ACA diagnostic criteria proposed by Dalmau and Graus were applied retrospectively to the ACA patients to examine the validity of the diagnoses. RESULTS: Among the 243 patients with CA, 13 were enrolled as ACA; five were PCD and eight were non-PCD. Eight of these cases met the proposed diagnostic criteria by Dalmau and Graus. MSA was the most prevalent disease among CA patients, with 93 cases. The incidence of cerebellar atrophy was significantly lower in ACA (3/13) than in MSA (92/92). Cerebrospinal fluid (CSF) pleocytosis was significantly more frequent in ACA than in MSA (4/13 vs. 2/55, respectively). However, there was no significant difference in the presence of oligoclonal bands, increased protein in CSF, and laterality differences in ataxia. CONCLUSION: ACA was present in ~ 5% of Japanese CA patients. The absence of cerebellar atrophy, despite the presence of CA, strongly supports ACA over MSA. While CSF pleocytosis was observed more often in ACA, the positivity rate was only ~ 30%. Since ACA is treatable, further studies are needed to identify additional clinical features and accurate diagnostic biomarkers.

Lambert-Eaton Myasthenic Syndrome Complicated by anti-GABAB Receptor Encephalitis.

A 74-year-old man experienced diplopia, generalized muscle weakness, and acute respiratory failure. He was diagnosed with Lambert-Eaton myasthenic syndrome (LEMS) and treated with immunotherapy, but no improvement was observed, and additional symptoms, including central apnea and hallucinations, appeared. Subsequent serum and cerebrospinal fluid (CSF) analyses confirmed the presence of GABAB receptor antibodies, indicating the coexistence of autoimmune encephalitis. Although there were no findings of malignancy, it is highly likely that occult small-cell lung carcinoma was present. When atypical symptoms occur in patients with LEMS, it is important to consider the possibility of concomitant autoimmune encephalitis.

Assessment for the timing of comprehensive genomic profiling tests in patients with advanced solid cancers.

Comprehensive genomic profiling (CGP) tests have been covered by public insurance in Japan for patients with advanced solid tumors who have completed or are completing standard treatments or do not have them. Therefore, genotype-matched drug candidates are often unapproved or off-label, and improving clinical trial access is critical, involving the appropriate timing of CGP tests. To address this issue, we analyzed the previous treatment data for 441 patients from an observational study on CGP tests discussed by the expert panel at Hokkaido University Hospital between August 2019 and May 2021. The median number of previous treatment lines was two; three or more lines accounted for 49%. Information on genotype-matched therapies was provided to 277 (63%). Genotype-matched clinical trials were ineligible because of an excess number of previous treatment lines or use of specific agents were found in 66 (15%) patients, with the highest proportion in breast and prostate cancers. Many patients met the exclusion criteria of one to two or more treatment lines across cancer types. In addition, previous use of specific agents was a frequent exclusion criterion for breast, prostate, colorectal, and ovarian cancers. The patients with tumor types with a low median number (two or fewer) of previous treatment lines, including most rare cancers, primary unknown cancers, and pancreatic cancers, had significantly fewer ineligible clinical trials. The earlier timing of CGP tests may improve access to genotype-matched clinical trials, with their proportion varying by cancer type. Each relevant society needs to advocate the desirable timing of CGP testing nationwide.

[Diagnosis of cryoglobulinemic vasculitis based on B symptoms and peripheral neuropathy: a case report].

A man in his 50s presented with a 2-month history of paresthesia and hypoesthesia of the extremities and B symptoms including low-grade fever, weight loss, and night sweats. He also reported a 3-year history of skin discoloration in cold weather. Laboratory test results showed a high white blood cell count and elevated serum C-reactive protein and rheumatoid factor (RF) levels. Complement levels were low, and tests for cryoglobulin showed positive results. Computed tomography revealed generalized lymphadenopathy, and 18F-fluorodeoxyglucose-positron emission tomography showed increased uptake; therefore, we performed cervical lymph node and muscle biopsies. The patient was diagnosed with nodular marginal zone lymphoma and cryoglobulinemic vasculitis (CV) and received chemotherapy and steroid treatment with improvement in symptoms. CV is a rare immune complex small-vessel vasculitis. It is important to measure RF and complement levels and consider infections, collagen diseases, and hematological disorders in the differential diagnosis in patients with suspected vasculitis or CV.

Novel partial deletions, frameshift and missense mutations of CSF1R in patents with CSF1R-related leukoencephalopathy.

BACKGROUND AND PURPOSE: Colony-stimulating factor 1 receptor (CSF1R)-related leukoencephalopathy is an adult-onset leukoencephalopathy caused by mutations in CSF1R. The present study aimed to explore the broader genetic spectrum of CSF1R-related leukoencephalopathy in association with clinical and imaging features. METHODS: Mutational analysis of CSF1R was performed for 100 consecutive patients with adult-onset leukoencephalopathy. Sequence and copy number variation (CNV) analyses of CSF1R were performed. The genomic ranges of the deletions were determined by long-read sequencing. Ligand-dependent autophosphorylation of CSF1R was examined in cells expressing the CSF1R mutants identified in this study. RESULTS: CSF1R mutations were identified in 15 patients, accounting for 15% of the adult-onset leukoencephalopathy cases. Seven novel and five previously reported CSF1R mutations were identified. The novel mutations, including three missense and one in-frame 3 bp deletion, were located in the tyrosine kinase domain (TKD) of CSF1R. Functional assays revealed that none of the novel mutations in the TKD showed autophosphorylation of CSF1R. Two partial deletions of CSF1R were identified that resulted in lack of the C-terminal region, including the distal TKD, in two patients. Various clinical features including cognitive impairment, psychiatric symptoms and gait disturbance were observed. Various degrees of the white matter lesions and corpus callosum abnormalities on magnetic resonance imaging and characteristic calcifications on computed tomography were observed as imaging features. CONCLUSIONS: Our results highlight the importance of examining the CNV of CSF1R even when Sanger or exome sequencing reveals no CSF1R mutations. Genetic examination of sequences and CNV analyses of CSF1R are recommended for an accurate diagnosis of CSF1R-related leukoencephalopathy.

Skin biopsies for diagnosing neuronal intranuclear inclusion disease: A retrospective study of 12 cases.

Neuronal intranuclear inclusion disease (NIID) is a progressive neurodegenerative condition. Skin biopsies taken from the lower leg were reported to be a standard diagnostic procedure for NIID; however, no studies have addressed the optimal skin biopsy locations. We retrospectively analyzed 12 cases in which skin biopsies were performed for diagnosing NIID. We collected clinical information including age, sex, skin biopsy site, the presence of nuclear inclusion bodies, the results of p62 immunostaining, the final diagnosis from the department of neurology, and the presence of abnormal GGC repeats in the NOTCH2NLC gene. Four of the 12 cases had a final diagnosis of NIID. One of the four cases was biopsied from the lower leg, whereas the other three cases were biopsied from the abdomen or thigh. Biopsy specimens of the four definite NIID cases revealed the average rates of nuclear inclusion body-positive cells in adipocytes, sweat gland cells, and fibroblasts to be 13.2%, 10.3%, and 6.3%, respectively. GGC repeat abnormalities in the NOTCH2NLC gene were observed in two of the four cases. The present study indicates that sites with ample subcutaneous fat tissue could be promising for diagnostic skin biopsies for NIID.

[A Case of Bing-Neel Syndrome With Repeated Long Spinal Cord Lesions].

The patient was a 45-year-old man. Since 2019, he had exhibited repeated steroid-improved dysuria and long spinal cord lesions. At the time of recurrence in June 2020, he exhibited a marked increase in serum IgM levels, suggesting hematopoietic disease. We found an MYD88 L265P mutation in cerebrospinal fluid cells, which subsequently led to the diagnosis of Bing-Neel syndrome (BNS). The patient was treated with Burton's tyrosine kinase inhibitors and his condition progressed without dysuria or worsening of the imaging findings. This case was challenging to differentiate from intractable inflammatory diseases; however, the identification of hyper-IgM helped in the diagnosis. BNS should be differentiated from central nervous system lesions through the identification of hyper-IgM.

Practice of Hereditary ATTR Amyloidosis in Non-endemic Areas of Japan.

Objective Hereditary ATTR (ATTRv) amyloidosis was once an incurable disease; however, in recent years, disease-modifying therapies, such as tafamidis and patisiran, have become available. We herein report the medical care situation in an ATTRv amyloidosis non-endemic area of Japan. Methods We confirmed the information in the medical records of our department and analyzed the data retrospectively. Patients Patients with ATTRv amyloidosis who were treated in our department between 2010 and 2021 were included. Results A total of 15 ATTRv amyloidosis cases (8 men and 7 women) were treated in our department during the study period; 9 patients had a family history, and the transthyretin V30M (p.V50M) gene mutation was present in 66% of cases. The average age of the onset was 57 years old, with 73% of the initial symptoms being dysesthesia and 13% being autonomic dysfunction. Ten patients were treated with tafamidis and nine with patisiran. Although it took a long time to start treatment among our experienced cases, there were some cases in which treatment could be introduced relatively early. Conclusion ATTRv amyloidosis is treatable and should be included in the differential diagnosis of neuropathy so that it can be diagnosed early and introduced into treatment. In the near future, the presymptomatic diagnosis of ATTRv amyloidosis and genetic counseling will become more important.

Current status and challenges of neurosurgical procedures for patients with myelomeningocele in real-world Japan.

BACKGROUND: Little is known about the real-world status of neurosurgical treatment of myelomeningocele patients. OBJECTIVE: To investigate the real-world status of neurosurgical treatment of myelomeningocele patients, medical claims data provided by the Japan Medical Data Center (JMDC) were analyzed. METHODS: The health claims data of 556 patients with myelomeningoceles from January 2005 to March 2020 were examined. The number of neurosurgical procedures, including myelomeningocele repair, tethered cord release, cerebrospinal fluid (CSF) shunt, CSF drainage, and endoscopic third ventriculostomy (ETV), was determined. RESULTS: A total of 313 neurosurgical procedures were performed for 135 patients in 74 institutions during the study period. The shunt survival rate was most affected by shunts that were revised when the patient was less than 1 year old, which had a significantly lower survival rate than all of the initial shunts performed when the patient was less than on1 year old; the 1-year shunt survival rate was 35 vs 64% (P = 0.0102). The survival rate was significantly lower in patients younger than 1 year who had CSF drainage before shunting compared to those younger than 1 year who did not have CSF drainage before shunting; the 1-year shunt survival rate was 27 vs 59% (P = 0.0196), and 81% of patients remained free of tethered cord release 10 years later. CONCLUSIONS: In this study, a revised shunt of less than 1 year of age and CSF drainage before shunting were the factors that lowered the shunt survival rate in the real world for CSF shunts for hydrocephalus associated with myelomeningocele.

Smoking and younger age at onset in anti-acetylcholine receptor antibody-positive myasthenia gravis.

Smoking is a known risk factor for the development and progression of several autoimmune diseases. Previous studies have pointed out the association of smoking with the development and worsening of symptoms in myasthenia gravis (MG), but further investigation is necessary to confirm this association. Smoking history was investigated in a cross-sectional study of 139 patients with anti-acetylcholine receptor antibody-positive MG, and the association of smoking history with the age at the onset of MG was analyzed. Patients who had been smoking at the onset of MG were significantly younger compared with those who had never smoked or had quit before the onset of MG. A linear regression analysis adjusting for sex and the presence/absence of thymoma showed a significant association between smoking at onset and younger age at onset (regression coefficient -9.05; 95% confidence interval, -17.6, -0.51; p = 0.039). Among patients with smoking exposure within 10 years prior to or at the onset of MG, women were significantly younger at the onset of MG compared with men. Our results suggest that smoking is an independent risk factor for the earlier development of anti-acetylcholine receptor antibody-positive MG and further support the putative link between smoking and MG.

Clinical features of anti-mitochondrial M2 antibody-positive myositis: case series of 17 patients.

OBJECTIVE: In 2012, a large number of myositis cases with anti-mitochondrial M2 (AMA-M2) antibody, which had well been known as the serological hallmark for primary biliary cholangitis (PBC), were reported in Japan. Recently, some case series from Japan, France, America, China and India have shown that approximately 2.5% to 19.5% of patients with myositis have AMA-M2 antibody. The objective of this study was to clarify the prevalence, clinical features, treatment outcome, and severity determinants of AMA-M2 positive myositis. METHODS: This study was a multicenter observational study. We enrolled patients who were diagnosed with myositis during a ten-year period between 2012 and 2021. RESULTS: Of the total of 185 patients with inflammatory myopathy, 17 patients were positive for AMA-M2 antibody. The typical symptoms were weakness mainly involving paravertebral muscles, weight loss, respiratory failure, and cardiac complications. Thirteen of the 17 patients had cardiac complications. A strong correlation was found between respiratory failure and modified Rankin Scale (mRS) score. A strong correlation was also found between respiratory failure and body weight, indicating that weight loss can be an indicator of potential progression of respiratory failure. Six of the 17 patients were complicated by malignancy. CONCLUSIONS: This study showed significant correlations between % vital capacity (VC), body mass index (BMI), and mRS score in patients with AMA-M2-positive myositis. Immunotherapy often improved CK level and respiratory dysfunction. We therefore propose that %VC and BMI should be monitored as disease indicators in treatment of AMA-M2-positive myositis.

Number of surgeries performed during the lifetime of patients with myelomeningocele.

OBJECTIVE: Patients with myelomeningocele often require multiple surgeries, but no study has clarified the kind of treatment given to these patients throughout their lives. The authors analyzed the type of surgery that was performed and at what age for Japanese patients with myelomeningoceles. METHODS: The Japanese health claims data of 556 patients with myelomeningocele for the period from January 2005 to March 2020 provided by the Japan Medical Data Center Co., Ltd., were examined to investigate the number of surgeries performed and the patient age at surgery for each specialty. The patients were divided into two groups (those ≤ 18 years old [group A] and those > 18 years old [group B]), and the way in which the types of surgery and the percentage of surgeries changed between these two groups was examined. RESULTS: The mean follow-up period was 4.4 years. The mean age at the end of the overall follow-up was 18.6 years (range 0-70.5 years), and 1033 surgeries were performed on 294 patients (0.42 surgeries performed per patient per year) during this period. The number of surgeries for patients in group A was 818 in 192 patients, with 0.62 surgeries per patient per year, and for patients in group B it was 215 in 102 patients, with 0.19 surgeries per patient per year. The number of surgeries and the mean age at the time of surgery were as follows: 313 neurosurgeries, 5.16 years; 280 orthopedic surgeries, 11.36 years; 70 urological surgeries, 14.57 years; and 202 dermatological/plastic surgeries, 16.19 years. In the surgeries related to myelomeningocele, the rates of CSF shunt placement, tethered cord release, muscle and tendon surgery, and other bone and joint surgery decreased significantly in group B, but they continued to undergo these surgeries. In group B, the rates of skin surgery, nephrostomy, ureterostomy, and cystostomy were significantly higher. CONCLUSIONS: A significant number of surgeries in multiple specialties related to myelomeningocele continue to be performed in adulthood, indicating that these patients require continuous care throughout their lives.

Rescue Extracranial-Intracranial Bypass for Ischemic Stroke Secondary to Progressive Human Immunodeficiency Virus-Associated Vasculopathy.

BACKGROUND: Human immunodeficiency virus (HIV) associated vasculopathy can cause ischemic cerebral stroke; however, there is limited evidence on optimal management. Herein, we report a case of acute ischemic stroke due to progressive internal carotid artery (ICA) stenosis in an HIV-positive patient. Superficial temporal artery to middle cerebral artery (STA-MCA) bypass, in addition to the best medical treatments, prevented stroke progression. CLINICAL DESCRIPTION: A 39-year-old man with HIV infection presented with a sudden onset of aphasia and right hemiparesis. Magnetic resonance imaging revealed an ischemic lesion in the left basal ganglia and concentric thickening of the vessel wall in the terminal portion of the bilateral ICAs. Despite maximal medical treatments for HIV-associated vasculopathy and possible opportunistic infections, bilateral ICA stenoses progressed, leading to a second hemodynamic stroke event. Because tissue plasminogen activator treatment failed, we performed STA-MCA bypass. A significant improvement in neurologic symptoms and cerebral blood flow was observed after surgery. No further stroke events occurred during the continuation of medical treatments. CONCLUSION: This is the first case of STA-MCA bypass performed in a patient with recurrent ischemic stroke caused by HIV-associated vasculopathy. Although further evidence is needed, such treatment options can shed new light on the management of progressive HIV-associated vasculopathy, which is refractory to maximal medical treatment.

Elderly patients with suspected Charcot-Marie-Tooth disease should be tested for the TTR gene for effective treatments.

BACKGROUND AND AIMS: Some hereditary transthyretin (ATTRv) amyloidosis patients are misdiagnosed as Charcot-Marie-Tooth disease (CMT) at onset. We assess the findings to identify ATTRv amyloidosis among patients with suspected CMT to screen transthyretin gene variants for treatments. METHODS: We assessed clinical, cerebrospinal fluid, and electrophysiological findings by comparing ATTRv amyloidosis patients with suspected CMT (n = 10) and CMT patients (n = 489). RESULTS: The median (interquartile range) age at onset of neurological symptoms was 69 (64.2-70) years in the ATTRv amyloidosis vs 12 (5-37.2) years in CMT group (Mann-Whitney U, p < 0.01). The proportion of patients with initial sensory symptoms was 70% in the ATTRv amyloidosis group vs 7.1% in CMT group (Fisher's exact, p < 0.01). The proportion of patients with histories of suspected chronic inflammatory demyelinating polyneuropathy (CIDP) were 50% in the ATTRv amyloidosis group vs 8.7% in CMT group (Fisher's exact, p < .01). Other measures and outcomes were not different between the two groups. Five of the six patients with ATTRv amyloidosis received treatment and survived. INTERPRETATION: For effective treatments, the transthyretin gene should be screened in patients with suspected CMT with old age at onset of neurological symptoms, initial sensory symptoms, and histories of suspected CIDP.

Association of Smoking and Generalized Manifestations of Myasthenia Gravis.

Objective Smoking is a known risk factor for the development and progression of autoimmune diseases. Previous studies in ocular myasthenia gravis (MG) patients showed that smoking is associated with the severity of symptoms and progression to generalized MG. However, whether smoking affects MG symptoms in patients with a broader clinical spectrum of presentations is unknown. Therefore, in this study, the associations of smoking with the clinical characteristics of MG were analyzed in a cohort of patients including those with generalized, seronegative, and thymoma-associated MG. Methods The smoking history was investigated in a cross-sectional study of 187 patients with MG followed in a referral hospital for neurology. The association of smoking with MG-activities of daily living score at survey, the presence of generalized manifestations, and the age of onset was assessed using multiple regression models. Results Neither current nor prior smoking habit was associated with the MG-activities of daily living score at survey. However, smoking exposure after MG onset was significantly associated with the presence of generalized manifestations during the disease course (odds ratio, 3.57; 95% confidence interval, 1.04, 12.3). The smoking history before or at onset of MG was not associated with the age of onset. Conclusion Smoking exposure after the onset is associated with generalized manifestations of MG in our cohort of patients with a broad clinical spectrum of presentations.

Progressive multifocal leukoencephalopathy with mild clinical conditions and detection of archetype-like JC virus in cerebrospinal fluid.

Progressive multifocal leukoencephalopathy (PML) is a demyelinating disease of the central nervous system with a poor prognosis and is primarily caused by JC virus (JCV) with a mutation called prototype. We encountered a case of PML with moderate progression and analyzed the mutational patterns of JCV in the cerebrospinal fluid (CSF). A 19-year-old Japanese woman with mild neurological symptoms was diagnosed with combined immunodeficiency following pneumocystis pneumonia. Brain magnetic resonance imaging scan showed multiple brain lesions, and real-time polymerase chain reaction testing detected JCV in the CSF, leading to the diagnosis of PML. The disease course of PML was stable after administration of mefloquine and mirtazapine with immunoglobulin replacement therapy. In the JCV genome cloned from the patient CSF, DNA sequences of the gene encoding the capsid protein (VP1) and the non-coding control region exhibited small mutations. However, they were quite similar to those of the archetype JCV, which persists asymptomatically in healthy individuals. These findings provide insight into the mutational characteristics of JCV in PML with mild symptoms and progression.