Affects: Cats
'Human eosinophilic granuloma is characterized by abnormal proliferation of Langerhans cells (LCs). LCs are antigen-presenting cells derived from dendritic cells. In humans, eosinophilic granulomas are considered to be benign tumors that occur mainly in children and adolescents. EG is a quite rare condition, and its incidence is higher in white than in black population, also slightly more affecting males than females. EG develops in 4-5 children (aged under 15) per million/year and in 1 or 2 adults per million/year.
The etiology of EG is not fully understood yet. However, the onset of abnormal LC proliferation may be triggered by viral stimuli (EBV, Human Herpes virus 6), bacterial toxins or defective regulation of IL-1 and IL-10 production. Another possible explanation may be a defect in Ras/MAPK signaling pathway due to mutation of signaling proteins. Particularly, it was published that about 50% of the EG cases had mutated BRAF V600 E gene and about 21% displayed a mutation in MAP2K1.
Signs And Symptoms: CEG usually manifests as a plaque on the palate, gums, lips or tongue. These are proliferative white or reddish lesions that may be painful and can be the cause of halitosis and hemorrhage that are often present. Loss of appetite is the most obvious symptom indicating the illness. The lesions may spontaneously appear and wane. Biopsy is usually required for confirmation of the diagnosis.
Diagnosis: Diagnostic options of EG comprise X-ray, CT and MR. Histopathological examination of the bioptic sample is focused on the presence of mononuclear LCs with prominent nuclear grooves (coffee bean shaped nuclei) with addition of eosinophils. Such examination also utilizes CD1 and CD207 (Langerin) staining. Electron microscopy examination of the sample is based on detection of Birbeck granules, specific "tennis racquet" shaped inclusion within cytoplasm of LCs.
Treatment: Although the etiology of the disease is not understood completely, it is believed that the most relevant triggers of the autoimmune reaction are various environmental stimuli, especially food allergens and insect bites. Thus, the treatment usually includes transition to hypoallergenic diet and protection from ectoparasites. Medication includes immunosuppressives (prednisone, azathioprine) either alone, or in combination with antibiotics or other drugs (cytostatics - chlorambucil). Remission of the lesions may occur in some cases, but in the others low doses of life-long immunosuppression may be necessary. Recent publications mention electrochemotherapy as a novel therapeutical method of CEG providing selective disappearance of the granuloma mass.