Posterior fossa progressive multifocal leukoencephalopathy: first presentation of an unknown autoimmune disease

Cerebellar progressive multifocal leucoencephalopathy identified by the shrimp sign

Progressive multifocal leucoencephalopathy (PML) is a demyelinating disease caused by the John Cunningham (JC) virus, which may get reactivated under certain immunosuppressive states such as AIDS, immunomodulatory therapy and haematological malignancies. PML has been reported rarely even in immunocompetent individuals where no immunodeficiency was present. PML characteristically involves periventricular and juxtacortical white matter. Isolated cerebellar or brainstem PML may be seen rarely. We present a case of a man in his 70s who presented with rapidly progressive cerebellar ataxia, ptosis and bipyramidal signs. Investigations excluded a direct viral cerebellar infection, acute disseminated encephalomyelitis, paraneoplastic cerebellar degeneration or any structural cerebellar lesion. MRI PET study revealed the classical shrimp sign which raised the possibility of cerebellar PML, and the same was confirmed by a positive JC virus PCR in the cerebrospinal fluid. Our patient had no known immune-compromising state, but further workup revealed a low CD4 count suggestive of idiopathic CD4 lymphopenia. The case illustrates the importance of the shrimp sign on MRI, the possibility of cerebellar involvement of PML as well as the need to consider a differential diagnosis of PML even in individuals with no obvious immunocompromised state.

Characteristics of Progressive Multifocal Leukoencephalopathy Associated With Sarcoidosis Without Therapeutic Immune Suppression

Importance

Progressive multifocal leukoencephalopathy can occur in the context of systemic sarcoidosis (S-PML) in the absence of therapeutic immune suppression and can initially be mistaken for neurosarcoidosis or other complications of sarcoidosis. Earlier recognition of S-PML could lead to more effective treatment of the disease.

Objective

To describe characteristics of patients with S-PML.

Design, Setting, and Participants

For this case series, records from 8 academic medical centers in the United States were reviewed from 2004 to 2022. A systematic review of literature from 1955 to 2022 yielded data for additional patients. Included were patients with S-PML who were not receiving therapeutic immune suppression. The median follow-up time for patients who survived the acute range of illness was 19 months (range, 2-99). Data were analyzed in February 2023.

Exposures

Sarcoidosis without active therapeutic immune suppression.

Main Outcomes and Measures

Clinical, laboratory, and radiographic features of patients with S-PML.

Results

Twenty-one patients with S-PML not receiving therapeutic immune suppression were included in this study, and data for 37 patients were collected from literature review. The median age of the 21 study patients was 56 years (range, 33-72), 4 patients (19%) were female, and 17 (81%) were male. The median age of the literature review patients was 49 years (range, 21-74); 12 of 34 patients (33%) with reported sex were female, and 22 (67%) were male. Nine of 21 study patients (43%) and 18 of 31 literature review patients (58%) had simultaneous presentation of systemic sarcoidosis and PML. Six of 14 study patients (43%) and 11 of 19 literature review patients (58%) had a CD4+ T-cell count greater than 200/μL. In 2 study patients, a systemic flare of sarcoidosis closely preceded S-PML development. Ten of 17 study patients (59%) and 21 of 35 literature review patients (60%) died during the acute phase of illness. No meaningful predictive differences were found between patients who survived S-PML and those who did not.

Conclusions and Relevance

In this case series, patients with sarcoidosis developed PML in the absence of therapeutic immune suppression, and peripheral blood proxies of immune function were often only mildly abnormal. Systemic sarcoidosis flares may rarely herald the onset of S-PML. Clinicians should consider PML in any patient with sarcoidosis and new white matter lesions on brain magnetic resonance imaging.

Treating sarcoidosis-associated progressive multifocal leukoencephalopathy with infliximab

Although most of the progressive multifocal leukoencephalopathy cases in sarcoidosis patients are explained by the treatment with immunosuppressive drugs, it is also reported in treatment-naive sarcoidosis patients, which implies a general predisposition of sarcoidosis patients for progressive multifocal leukoencephalopathy. Indeed, it was shown that active sarcoidosis patients have increased regulatory T cell frequencies which could lead to a subsequent systemic immunosuppression. However, if sarcoidosis with systemic changes of T cell subsets frequencies constitute a risk factor for the development of progressive multifocal leukoencephalopathy, which could then be counteracted by sarcoidosis treatment, is not known. In this cohort study, we included, characterized and followed-up six patients with bioptically confirmed definite progressive multifocal leukoencephalopathy and definite or probable sarcoidosis presenting between April 2013 and January 2019, four of them had no immunosuppressive therapy at the time of developing first progressive multifocal leukoencephalopathy symptoms. Analysis of immune cell subsets in these patients revealed significant imbalances of CD4⁺ T cell and regulatory T cell frequencies. Due to the progression of progressive multifocal leukoencephalopathy in four patients, we decided to treat sarcoidosis anticipating normalization of immune cell subset frequencies and thereby improving progressive multifocal leukoencephalopathy. Notably, by treatment with infliximab, an antibody directed against tumour necrosis factor-α, three patients continuously improved clinically, JC virus was no longer detectable in the cerebrospinal fluid and regulatory T cell frequencies decreased. One patient was initially misdiagnosed as neurosarcoidosis and died 9 weeks after treatment initiation due to aspiration pneumonia. Our study provides insight that sarcoidosis can lead to changes in T cell subset frequencies, which predisposes to progressive multifocal leukoencephalopathy. Although immunosuppressive drugs should be avoided in progressive multifocal leukoencephalopathy, paradoxically in patients with sarcoidosis treatment with the immunosuppressive infliximab might restore normal T cell distribution and thereby halt progressive multifocal leukoencephalopathy progression.

Progressive Multifocal Leukoencephalopathy: Current Insights

Cases of PML should be evaluated according to predisposing factors, as these subgroups differ by incidence rate, clinical course, and prognosis. The three most significant groups at risk of PML are patients with hematological malignancies mostly previously treated with immunotherapies but also untreated, patients with HIV infection, and patients using monoclonal antibody (mAb) treatments. Epidemiological data is scarce and partly conflicting, but the distribution of the subgroups appears to have changed. While there is no specific anti-JCPyV treatment, restoration of the immune function is the most effective approach to PML treatment. Research is warranted to determine whether immune checkpoint inhibitors could benefit certain PML subgroups. There are no systematic national or international records of PML diagnoses or a risk stratification algorithm, except for MS patients receiving natalizumab (NTZ). These are needed to improve PML risk assessment and to tailor better prevention strategies.

Susceptibility-Weighted MR Imaging Hypointense Rim in Progressive Multifocal Leukoencephalopathy: The End Point of Neuroinflammation and a Potential Outcome Predictor

BACKGROUND AND PURPOSE

Progressive multifocal leukoencephalopathy (PML) represents a life-threatening demyelinating disorder of the brain caused by reactivation of a rare opportunistic infection with JC Polyomavirus. The aims of this study were to describe the incidence of a susceptibility-weighted imaging hypointense rim in patients with multifocal leukoencephalopathy and to explore the histologic correlates and prognostic value of the rim with regard to the clinical outcome.

MATERIALS AND METHODS

This retrospective study included 18 patients with a definite diagnosis of progressive multifocal leukoencephalopathy. Ten patients were HIV-positive, 3 patients had natalizumab-associated progressive multifocal leukoencephalopathy, 1 patient had multiple myeloma, 3 patients had a history of lymphoma, and 1 was diagnosed with acute myeloid leukemia. Patients were divided into short- (up to 12 months) and long-term (>12 months) survivors. A total of 93 initial and follow-up MR imaging examinations were reviewed. On SWI, the presence and development of a hypointense rim at the periphery of the progressive multifocal leukoencephalopathy lesions were noted. A postmortem histologic examination was performed in 2 patients: A rim formed in one, and in one, there was no rim.

RESULTS

A total of 73 progressive multifocal leukoencephalopathy lesions were observed. In 13 (72.2%) patients, a well-defined thin, linear, hypointense rim at the periphery of the lesion toward the cortical side was present, while in 5 (27.8%) patients, it was completely absent. All 11 long-term survivors and 2 short-term survivors presented with a prominent SWI-hypointense rim, while 5/7 short-term survivors did not have this rim.

CONCLUSIONS

The thin, uniformly linear, gyriform SWI-hypointense rim in the paralesional U-fibers in patients with definite progressive multifocal leukoencephalopathy might represent an end-point stage of the neuroinflammatory process in long-term survivors.