BACKGROUND: The Triggering Receptor Expressed on Myeloid Cells 2 protein (TREM2) plays a crucial role in various biological processes, including osteoclast differentiation, and disease-associated microglia (DAM) activation to regulate neuroinflammation, and phagocytosis in the brain. Genetic variations in TREM2 are implicated in neurodegenerative disorders, such as Nasu-hakola disease (NHD), characterized by bone lesions, neuropsychiatric disorders, and early-onset dementia.
METHODS: We studied 3 siblings with suspected NHD. Whole-exome sequencing was conducted on the proband to identify the possible genetic cause(s) and by Sanger sequencing to validate the identified variants in the two other affected siblings, a healthy sister, and the parents.
RESULTS: We identified a novel homozygous deletion (c.549del; p.(Leu184Serfs*5)) in TREM2. Our literature review reveals 16 TREM2 mutations causing early-onset dementia and bone lesions.
CONCLUSIONS: These findings, alongside previous research, elucidate the clinical spectrum of TREM2-related diseases, aiding accurate diagnosis and patient care. This knowledge is vital for understanding TREM2-dependent DAM and its involvement in the pathogenesis of neurodevelopmental disorders which can help to develop targeted therapies and improve outcomes for TREM2-affected individuals.

UNASSIGNED: Subacute Sclerosing Panencephalitis (SSPE) typically presents with periodic myoclonus; however, a spectrum of movement disorders including dystonia, chorea, tremor, and parkinsonism have also been described. This review aims to evaluate the array of movement disorders in SSPE, correlating them with neuroimaging findings, disease stages, and patient outcomes.
UNASSIGNED: A comprehensive review of published case reports and case series was conducted on patients with SSPE exhibiting movement disorders other than periodic myoclonus. PRISMA guidelines were followed, and the protocol was registered with PROSPERO (2023 CRD42023434650). A comprehensive search of multiple databases yielded 37 reports detailing 39 patients. Dyken\'s criteria were used for SSPE diagnosis, and the International Movement Disorders Society definitions were applied to categorize movement disorders.
UNASSIGNED: The majority of patients were male, with an average age of 13.8 years. Approximately, 80% lacked a reliable vaccination history, and 39% had prior measles infections. Dystonia was the most common movement disorder (49%), followed by parkinsonism and choreoathetosis. Rapid disease progression was noted in 64% of cases, with a disease duration of ≤6 months in 72%. Neuroimaging showed T2/FLAIR MR hyperintensities, primarily periventricular, with 26% affecting the basal ganglia/thalamus. Brain biopsies revealed inflammatory and neurodegenerative changes. Over half of the patients (56%) reached an akinetic mute state or died.
UNASSIGNED: SSPE is associated with diverse movement disorders, predominantly hyperkinetic. The prevalence of dystonia suggests basal ganglia dysfunction.

BACKGROUND: Subacute sclerosing panencephalitis (SSPE) is a complication of measles, occurring after a latency of 4-10 years. It continues to occur in developing countries although resurgence is being reported from developed countries. Characteristic features include progressive neuropsychiatric issues, myoclonus, seizures, movement disorders and visual impairment. Electroencephalography (EEG) typically shows periodic generalized discharges, and elevated CSF anti-measles antibodies are diagnostic. Movement disorders are being increasingly recognized as part of the clinical spectrum, and range from hyperkinetic (chorea, dystonia, tremor, tics) to hypokinetic (parkinsonism) disorders and ataxia.
OBJECTIVE: This article aims to comprehensively review the spectrum of movement disorders associated with SSPE.
METHODS: A literature search was conducted in PubMed and EMBASE databases in December 2023 and articles were identified for review.
RESULTS: Movement disorders reported in SSPE included hyperkinetic (chorea, dystonia, tremor and tics), hypokinetic (parkinsonism), ataxia and extraocular movement disorders. Myoclonus, a core clinical feature, was the most frequent \"abnormal movement.\" Movement disorders were observed in all clinical stages, and could also be a presenting feature, even sans myoclonus. Hyperkinetic movement disorders were more common than hypokinetic movement disorders. An evolution of movement disorders was observed, with ataxia, chorea and dystonia occurring earlier, and parkinsonism later in the disease. Neuroradiological correlates of movement disorders remained unclear.
CONCLUSIONS: A wide spectrum of movement disorders was observed throughout the clinical stages of SSPE. Most data were derived from case reports and small case series. Multicentric longitudinal studies are required to better delineate the spectrum and evolution of movement disorders in SSPE.

Measles inclusion-body encephalitis (MIBE) is rare, with insights largely from case studies. We systematically analyzed subacute Sclerosing Panencephalitis (SSPE) cases in immunocompromised patients, identifying distinctive clinical and neuroimaging features. These findings could facilitate MIBE diagnosis without the need for brain biopsies. Our systematic review on MIBE and HIV-related SSPE adhered to PRISMA guidelines and was registered with PROSPERO. We searched multiple databases and followed a detailed inclusion process with independent reviews and quality assessment. Data on patient demographics, clinical features, and outcomes were compiled. A review of 39 studies on 49 MIBE patients and 8 reports on HIV-positive SSPE patients was conducted. Acute lymphoblastic leukemia, HIV, organ transplants, and malignancies were common precursors to MIBE. Perinatal HIV was prevalent among SSPE cases. Seizures were the primary symptom in MIBE, often drug-resistant and progressing to status epilepticus or epilepsia partialis continua, whereas periodic myoclonus was universal in SSPE. Neuroimaging showed distinct patterns for each group, and histopathology confirmed measles virus presence in 39% of MIBE cases. MIBE patients typically progressed to coma and death. In conclusion, MIBE and SSPE in HIV-infected patients present with distinct clinical pictures but identical brain pathological abnormalities.

Subacute sclerosing panencephalitis is a rare complication due to persistent measles infection, characterized by cognitive and motor deterioration. Because subacute sclerosing panencephalitis is considered a potentially fatal complication of measles and usually presents in young populations, particularly those with measles infection under the age of 2 years, new approaches to implement vaccination programs must be devised to help avoid the worsening of patient outcome. Until the disease is eradicated globally, children in all regions of the world remain at risk of measles infection and its respective complications, and therefore, the vaccine is considered the optimal preventative measure. The legacy of measles virus goes beyond the immediate complications. Our study, therefore, aims to provide a comprehensive review on the updated insights into subacute sclerosing panencephalitis as a complication, as well as the extent and future considerations pertaining to vaccination programs in the pediatric population.

Data related to psychiatric manifestations in subacute sclerosing panencephalitis (SSPE) is currently available only in the form of isolated case reports. In this systematic review, we evaluated the spectrum of psychiatric manifestations and their impact on the course and outcome of SSPE. Data were obtained from 4 databases (PubMed, Embase, Scopus, and Google Scholar), with the most recent search conducted on March 27, 2023. The PRISMA guidelines were followed, and the PROSPERO registration number for the protocol is CRD42023408227. SSPE was diagnosed using Dyken\'s criteria. Extracted data were recorded in an Excel spreadsheet. To evaluate the quality of the data, the Joanna Briggs Institute Critical Appraisal tool was employed. Our search resulted in 30 published reports of 32 patients. The mean age was 17.9 years. Schizophrenia, catatonia, and poorly characterized psychotic illnesses were the 3 most common psychiatric presentations that were seen in 63% (20/32) of cases. Catatonia was seen in 4 patients. Affective disorders, mania, and depression were reported among 22% (7/32) cases. In approximately 81% (26/32) cases, the course of SSPE was acute fulminant. Treatment with antipsychotic drugs had poor or no response. Out of 17 patients, who received antipsychotic drugs, 6 patients noted severe extrapyramidal adverse effects. SSPE often masquerades as a psychiatric disorder. Unresponsive psychiatric symptoms, early extrapyramidal signs, and progressive encephalopathy indicate SSPE.

Vision loss is a presenting complaint in many patients with subacute sclerosing panencephalitis (SSPE). Data related to vision loss in SSPE is available only in the form of case reports. In this systematic review, we evaluated characteristics of vision loss, affected anatomic site, and patient course and outcome. We extracted data from four databases: PubMed, Embase, Scopus, and Google Scholar. The last search was done on October 26, 2022. We adhered to Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. The protocol was registered with PROSPERO (CRD42022362652). Dyken\'s criteria were used for the diagnosis of SSPE. The data were recorded in an Excel sheet. The Joanna Briggs Institute Critical Appraisal tool was used to assess the quality of data. The mean age of patients with SSPE was 17.9 years. Males outnumbered females (60:34). In 73 patients (76%), duration of illness/onset of vision loss was less than 6 months. In 76% patients (n = 73), visual manifestations appeared before encephalopathy. Involvement of the retina (58 of 96, 60.4%), optic nerve (9 of 96, 9.3%), or cerebral cortex (29 of 96, 30.2%) was responsible for vision loss. T2/fluid-attenuated inversion recovery (FLAIR) magnetic resonance imaging (MRI) parieto-occipital hyperintensities were the most frequent (71.4%) neuroimaging abnormality. Retinal biopsy revealed similar findings revealed by brain histopathology. All patients died and became akinetic mute during the follow-up period, which ranged from a few weeks to a few years. In conclusion, retinal involvement was the most common cause of vision loss. Vision loss often precedes encephalopathy. Cortical vision loss was associated invariably with T2/FLAIR MRI hyperintensities in the parieto-occipital region.

BACKGROUND: Subacute sclerosing panencephalitis (SSPE) is a devastating brain disease caused by persistent infection by the measles virus. Several cases of SSPE in pregnant ladies have been described. This systematic review is focused on maternal and foetal outcomes among pregnant women with SSPE.
METHODS: We searched four databases (PubMed, Embase, Scopus, and Google Scholar). We reviewed all relevant cases, published until 14 August 2022. The review was conducted following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. The protocol was registered with PROSPERO (CRD42022348630). The search items that we used were \"((Pregnancy) OR (delivery)) AND (Subacute sclerosing panencephalitis (SSPE))\". Dyken\'s criteria were used for the diagnosis of SSPE in pregnant women. The extracted data was recorded in an Excel sheet. The Joanna Briggs Institute Critical Appraisal tool for case reports was used to assess the quality of published cases.
RESULTS: We came across 19 reports describing details of 21 cases. The age of SSPE-affected women varied from 14 to 34 years (mean 23 years). In the majority (n=14), clinical manifestations were started in the antepartum period. Nine pregnant SSPE women presented with vision loss. After delivery, 13 SSPE-affected women died. On the contrary, 15 foetuses, though the majority were preterm, were alive. Five foetuses either died soon after birth or were still-born.
CONCLUSIONS: In conclusion, SSPE in pregnancy is often missed, as it mimics eclampsia. SSPE in pregnancy usually has a devastating course. Universal early childhood measles vaccination is the only way to fight this menace.

Primary microglial leukodystrophy or leukoencephalopathy are disorders in which a genetic defect linked to microglia causes cerebral white matter damage. Pigmented orthochromatic leukodystrophy, adult-onset orthochromatic leukodystrophy associated with pigmented macrophages, hereditary diffuse leukoencephalopathy with (axonal) spheroids, and adult-onset leukoencephalopathy with axonal spheroids and pigmented glia (ALSP) are different terms apparently used to designate the same disease. However, ALSP linked to dominantly inherited mutations in CSF1R (colony stimulating factor receptor 1) cause CSF-1R-related leukoencephalopathy (CRP). Yet, recessive ALSP with ovarian failure linked to AARS2 (alanyl-transfer (t)RNA synthase 2) mutations (LKENP) is a mitochondrial disease and not a primary microglial leukoencephalopathy. Polycystic membranous lipomembranous osteodysplasia with sclerosing leukoencephalopathy (PLOSL; Nasu-Hakola disease: NHD) is a systemic disease affecting bones, cerebral white matter, selected grey nuclei, and adipose tissue The disease is caused by mutations of one of the two genes TYROBP or TREM2, identified as PLOSL1 and PLOSL2, respectively. TYROBP associates with receptors expressed in NK cells, B and T lymphocytes, dendritic cells, monocytes, macrophages, and microglia. TREM2 encodes the protein TREM2 (triggering receptor expressed on myeloid cells 2), which forms a receptor signalling complex with TYROBP in macrophages and dendritic cells. Rather than pure microglial leukoencephalopathy, NHD can be considered a multisystemic \"immunological\" disease.

Subacute sclerosing panencephalitis (SSPE) is a slowly progressive neurodegenerative disease caused by the measles virus. This study investigated the magnetic resonance imaging (MRI) findings in SSPE by retrospective review of two cases diagnosed by typical periodic electroencephalographic (EEG) features, clinical symptoms and elevated measles antibody titre in cerebrospinal fluid (CSF). MRI revealed lesions of high signal intensity on T2-weighted images involving the periventricular or subcortical white matter in both the patients. Both these patients were given sodium valproate for seizures. However, the disease proved fatal in both these cases eventually.