Haploinsufficiency of CSF-1R and clinicopathologic characterization in patients with HDLS.

OBJECTIVE: To clarify the genetic, clinicopathologic, and neuroimaging characteristics of patients with hereditary diffuse leukoencephalopathy with spheroids (HDLS) with the colony stimulating factor 1 receptor (CSF-1R) mutation. METHODS: We performed molecular genetic analysis of CSF-1R in patients with HDLS. Detailed clinical and neuroimaging findings were retrospectively investigated. Five patients were examined neuropathologically. RESULTS: We found 6 different CSF-1R mutations in 7 index patients from unrelated Japanese families. The CSF-1R mutations included 3 novel mutations and 1 known missense mutation at evolutionarily conserved amino acids, and 1 novel splice-site mutation. We identified a novel frameshift mutation. Reverse transcription PCR analysis revealed that the frameshift mutation causes nonsense-mediated mRNA decay by generating a premature stop codon, suggesting that haploinsufficiency of CSF-1R is sufficient to cause HDLS. Western blot analysis revealed that the expression level of CSF-1R in the brain from the patients was lower than from control subjects. The characteristic MRI findings were the involvement of the white matter and thinning of the corpus callosum with signal alteration, and sequential analysis revealed that the white matter lesions and cerebral atrophy relentlessly progressed with disease duration. Spotty calcifications in the white matter were frequently observed by CT. Neuropathologic analysis revealed that microglia in the brains of the patients demonstrated distinct morphology and distribution. CONCLUSIONS: These findings suggest that patients with HDLS, irrespective of mutation type in CSF-1R, show characteristic clinical and neuroimaging features, and that perturbation of CSF-1R signaling by haploinsufficiency may play a role in microglial dysfunction leading to the pathogenesis of HDLS.

CSF1R mutations in hereditary diffuse leukoencephalopathy with spheroids are loss of function.

Hereditary diffuse leukoencephalopathy with spheroids (HDLS) in humans is a rare autosomal dominant disease characterized by giant neuroaxonal swellings (spheroids) within the CNS white matter. Symptoms are variable and can include personality and behavioural changes. Patients with this disease have mutations in the protein kinase domain of the colony-stimulating factor 1 receptor (CSF1R) which is a tyrosine kinase receptor essential for microglia development. We investigated the effects of these mutations on Csf1r signalling using a factor dependent cell line. Corresponding mutant forms of murine Csf1r were expressed on the cell surface at normal levels, and bound CSF1, but were not able to sustain cell proliferation. Since Csf1r signaling requires receptor dimerization initiated by CSF1 binding, the data suggest a mechanism for phenotypic dominance of the mutant allele in HDLS.

Parkinsonian features in hereditary diffuse leukoencephalopathy with spheroids (HDLS) and CSF1R mutations.

Atypical Parkinsonism associated with white matter pathology has been described in cerebrovascular diseases, mitochondrial cytopathies, osmotic demyelinating disorders, leukoencephalopathies leukodystrophies, and others. Hereditary diffuse leukoencephalopathy with spheroids (HDLS) is an autosomal dominant disorder with symptomatic onset in midlife and death within a few years after symptom onset. Neuroimaging reveals cerebral white matter lesions that are pathologically characterized by non-inflammatory myelin loss, reactive astrocytosis, and axonal spheroids. Most cases are caused by mutations in the colony-stimulating factor 1 receptor (CSF1R) gene. We studied neuropathologically verified HDLS patients with CSF1R mutations to assess parkinsonian features. Ten families were evaluated with 16 affected individuals. During the course of the illness, all patients had at least some degree of bradykinesia. Fifteen patients had postural instability, and seven had rigidity. Two patients initially presented with parkinsonian gait and asymmetrical bradykinesia. These two patients and two others exhibited bradykinesia, rigidity, postural instability, and tremor (two with resting) early in the course of the illness. Levodopa/carbidopa therapy in these four patients provided no benefit, and the remaining 12 patients were not treated. The mean age of onset for all patients was about 45 years (range, 18-71) and the mean disease duration was approximately six years (range, 3-11). We also reviewed HDLS patients published prior to the CSF1R discovery for the presence of parkinsonian features. Out of 50 patients, 37 had gait impairments, 8 rigidity, 7 bradykinesia, and 5 resting tremor. Our report emphasizes the presence of atypical Parkinsonism in HDLS due to CSF1R mutations.

Adult-onset leukoencephalopathy with axonal spheroids and pigmented glia: report on a case with morphometric studies.

Two previously distinct leukodystrophies, pigmentary orthochromatic leukodystrophy and hereditary diffuse leukoencephalopathy with spheroids, have recently been interpreted as variants of the same disease, adult-onset leukoencephalopathy with spheroids and pigmented glia (ALSP). We report a sporadic case of a 56-year-old male with ALSP presenting as frontotemporal dementia behavioral variant (FTD-bv). He had a history of depression and developed socially inappropriate behaviors consistent with FTD-bv. His first neurological exam was normal, but he developed new symptoms in the next 1.5 years: executive functional difficulties, anosognosia, urinary incontinence, epilepsy, extrapyramidal syndrome, severe gait disturbance, dysarthria, dysphagia and mutism. He died of pneumonia 20 months after initial presentation. MRI revealed increased T2-FLAIR signal in periventricular white matter and corpus callosum atrophy. Histology showed extensive demyelination of the centrum semiovale, most severe in frontal and temporal lobes, sparing U-fibers. There was no cortical neuronal loss, but selective loss of thalamic neurons. Histopathological hallmarks were cortical neuronal ballooning, white matter orthochromasia, pigmented macrophages, oligodendroglial loss, and axonal spheroids, some myelinated and some vacuolated. Morphometric studies for myelin, spheroids, oligodendrocytes and astrocytes showed that: 1) spheroids were most abundant in areas of partial demyelination rather than areas of extensive demyelination, being absent in normal appearing areas, 2) oligodendrocyte loss only occurred in regions of extensive demyelination and not in partial demyelination, and 3) there was no statistically significant change in number of astrocytes. There were also many more spheroids than physiologically expected in the gracile and cuneate nuclei. These findings suggest that the formation of spheroids is an early-stage event in disease progression. *These authors contributed equally to this work.

[Rehabilitation on functional amblyopia in Morning Glory Syndrome]. / Rééducation de la part fonctionnelle de l'amblyopie dans un Morning Glory syndrome.

INTRODUCTION: Morning Glory syndrome, characterized by an enlarged dysplasic optic disc with glial tissue, is one of the congenital anomalies of the optic nerve. This syndrome is rare, prevalent in the girls, and generally unilateral. It can be revealed with nystagmus, strabismus, or amblyopia. OBSERVATION: We report the clinical observation of a 2.5-year-old girl, referred for the diagnosis of Morning Glory syndrome in the left eye with severe amblyopia (1/10 Rossano 1/20) and esotropia. This syndrome has associated central nervous system anomalies with a basal encephalocele. Treated with functional amblyopia therapy, visual acuity was 7/10 Rossano 1/2 after 1 year. DISCUSSION: Rehabilitation on functional amblyopia in organic optic nerve anomalies is essential. A child with a Morning Glory syndrome, detected during the period of sensory maturation, must be treated with occlusion therapy, followed by maintenance treatment. This part of the treatment can prevent deep amblyopia. Moreover, regular ophthalmologic follow-up to detect complications of retinal detachment and multidisciplinary follow-up to detect a cytogenetic disease, CHARGE syndrome, or association with endocrine and central nervous system anomalies are necessary. CONCLUSION: The author recommends occlusion therapy for children with Morning Glory syndrome or other organic asymmetric optic nerve anomalies, during the period of amblyopia reversibility. Most patients' vision improves after treatment. This case is an illustration.

Correlation of EEG, neuroimaging and histopathology in an epilepsy patient with diffuse cortical dysplasia.

The correlation between scalp EEG, intraoperative electrocorticogram, neuroimaging and histopathology was examined in an epileptic child with diffuse cortical dysplasia. The 6-year-old girl with moderate mental retardation had suffered from intractable complex partial and generalized epilepsies since the age of 2 years. MR images demonstrated unilateral large macrogyria/polymicrogyria and schizencephaly in the right occipital lobe. The epileptic focus was detected on the macrogyria by EEG and single photon emission tomography. However, the intraoperative electrocorticogram showed frequent spikes from the polymicrogyria and no paroxysmal activity in the macrogyria. The polymicrogyria and the macrogyric lesion were resected, using an image-guided system. The histological findings revealed that the macrogyria was covered with and separated by glial bundles. It has been reported that epileptogenicity is produced from abnormal neurons and their arrangement in cortical dysplasia; in this case, however, the major dysplastic lesion had no epileptogenicity; rather the focus might be in the polymicrogyria around the lesion.