Neuronal cytoplasmic inclusion bodies in the brain of Lagotto Romagnolo dogs: A qualitative and quantitative histologic evaluation.

Abstract

Four neurologic diseases affect dogs of the Lagotto Romagnolo (LR) breed, namely benign familial juvenile epilepsy (BFJE), vacuolar storage disease, and 2 forms of cerebellar cortical degeneration. Intraneuronal inclusion bodies in cerebellar Purkinje cells were first described in the BFJE phenotype. Upon further characterization of these diseases, similar inclusions were also noted in the brain of LRs used as controls. This study investigated the clinical, histologic, and electron microscopic findings in 23 LRs to determine the nature of their neuronal inclusions and whether the presence, distribution, or number of inclusions is associated with neurologic signs. Electron microscopy of the inclusions revealed a cytoplasmic aggregate without a limiting membrane. The inclusions appeared proteinaceous on histochemical staining and positive on phosphotungstic-acid-hematoxylin (PTAH) stain for proteins rich in basic amino acids. Markers of commonly known proteinopathies of humans (ubiquitin, p62, LC3, α-synuclein, and β-amyloid) were not detected in the inclusions when assessed by immunohistochemistry. The overall presence of inclusion bodies was not significantly associated with the dog's neurologic status. The results show an association between inclusions in the cerebral cortex and an absence of clinical neurologic disease in LRs. There was no significant difference in the quantitative inclusion body burden when compared in LRs with or without neurologic signs. Although PTAH-positive proteinaceous neuronal inclusions are a common finding in LRs regardless of neurologic signs, these inclusions may be a protective response when present in the cerebral cortex.