Unexpected Occurrence of Fetal Hemophagocytic Syndrome in a Patient with Hereditary Diffuse Leukoencephalopathy with Spheroids

Colony stimulating factor-1 receptor (CSF1R) plays important roles in the differentiation and proliferation of macrophage and microglia in systemic organs and the brain. A genetic defect in CSF1R causes hereditary diffuse leukoencephalopathy with spheroids (HDLS). HDLS mainly affects the cerebral white matter and shows pre-senile cognitive decline, motor disturbance, and epilepsy. However, systemic manifestations outside the brain have not yet been described in patients with HDLS. Here, we report the case of a 41-year-old man with HDLS carrying the p. K793T mutation in CSF1R, who unexpectedly died of sepsis and hemophagocytic syndrome shortly after the onset of HDLS. The fetal sequence of sepsis and hemophagocytic syndrome was triggered by enterocolitis. An autopsy revealed that focal inflammation in the intestine had almost resolved. Most strikingly, massive infiltration of cluster of differentiation (CD) 68- and CD163-immunopositive macrophages with hemophagocytosis was observed in the bone marrow, spleen, and liver. Less abundant infiltration of CD68- and CD204-immunopositive macrophages without hemophagocytosis was also seen in the lung and intestine. At present, the pathogenetic link between CSF1R mutation and hemophagocytic syndrome in this patient is unclear. Our case, however, clearly shows that even in patients with HDLS, aberrant activation of functional macrophages can be induced under certain conditions in visceral organs.

Clinicopathologic characterization and abnormal autophagy of CSF1R-related leukoencephalopathy

Background:CSF1R-related leukoencephalopathy,also known as hereditary diffuse leukoencephalopathy with spheroids(HDLS),is a rare white-matter encephalopathy characterized by motor and neuropsychiatric symptoms due to colony-stimulating factor 1 receptor(CSF1R)gene mutation.Few of CSF1R mutations have been functionally testified and the pathogenesis remains unknown.Methods:In order to investigate clinical and pathological characteristics of patients with CSF1R-related leukoencephalopathy and explore the potential impact of CSF1R mutations,we analyzed clinical manifestations of 15 patients from 10 unrelated families and performed brain biopsy in 2 cases.Next generation sequencing was conducted for 10 probands to confirm the diagnosis.Sanger sequencing,segregation analysis and phenotypic reevaluation were utilized to substantiate findings.Functional examination of identified mutations was further explored.Results:Clinical and neuroimaging characteristics were summarized.The average age at onset was 35.9±6.4 years(range 24–46 years old).Younger age of onset was observed in female than male(34.2 vs.39.2 years).The most common initial symptoms were speech dysfunction,cognitive decline and parkinsonian symptoms.One patient also had marked peripheral neuropathy.Brain biopsy of two cases showed typical pathological changes,including myelin loss,axonal spheroids,phosphorylated neurofilament and activated macrophages.Electron microscopy disclosed increased mitochondrial vacuolation and disorganized neurofilaments in ballooned axons.A total of 7 pathogenic variants(4 novel,3 documented)were identified with autophosphorylation deficiency,among which c.2342C>T remained partial function of autophosphorylation.Western blotting disclosed the significantly lower level of c.2026C>T(p.R676*)than wild type.The level of microtubule associated protein 1 light chain 3-II(LC3-II),a classical marker of autophagy,was significantly lower in mutants expressed cells than wild type group by western blotting and immunofluorescence staining.Conclusions:Our findings support the loss-of-function and haploinsufficiency hypothesis in pathogenesis.Autophagy abnormality may play a role in the disease.Repairing or promoting the phosphorylation level of mutant CSF1R may shed light on therapeutic targets in the future.However,whether peripheral polyneuropathy potentially belongs to CSF1R-related spectrum deserves further study with longer follow-up and more patients enrolled.