# Pulmonary Langerhans Cell Histiocytosis in an African Lion: A Rare Case Report

## TL;DR

This paper reports a rare case of a lung disease in an African lion, confirmed through pathological and immunohistochemical analysis.

## Contribution

This is the first documented case of pulmonary Langerhans cell histiocytosis in an African lion, providing new insights into this rare feline disease.

## Key findings

- The African lion exhibited severe respiratory failure and lung infiltration by Langerhans cells.
- Histopathological and immunohistochemical analyses confirmed the diagnosis of PLCH.
- The case highlights the disease's impact on multiple organs beyond the lungs.

## Abstract

Feline pulmonary Langerhans cells histiocytosis (PLCH) is a rare disease that results in respiratory failure due to the infiltration of Langerhans cells (LCs) in the lungs. A diagnosis of PLCH is proposed based on the clinical signs and pathological findings and confirmed based on the infiltrating histiocytic cells. Here, we present a rare case of PLCH in an African lion. The disease mainly affected the lungs with variable and limited involvement of other organs. While a definite clinical diagnosis is difficult, the pulmonary pathological changes with nodular appearance and infiltration of LCs, together with the immunohistochemistry results, are sufficient for diagnostic confirmation of PLCH. To our knowledge, this is the first reported PLCH case in an African lion, and this case report could present new information and aspects of this feline histiocytic disease.

Background: Feline pulmonary Langerhans cells histiocytosis (PLCH) is a rare disorder that results in progressive respiratory failure secondary to pulmonary parenchymal infiltration with Langerhans cells (LCs). A diagnosis of PLCH is proposed based on the clinical features and pathological findings and confirmed based on the infiltrating histiocytic cells. There are few documented cases of feline PLCH, and this case report of PLCH in an African Lion could present new information and aspects of this feline histiocytic disease. Case presentation: An African lion at Hohhot Zoo showing severe hyporexia and dyspnea with subsequent mental depression and emaciation died of exhaustion after a 35-day course of illness. Empirical treatment did not have a significant effect. An autopsy revealed that the lungs were enlarged and hardened due to infiltrative lesions, with many yellowish-white foci in all the lobes and sections. Furthermore, the kidneys were atrophied and had scattered grayish-white lesions on the surface. At the same time, congestion was widely distributed in various locations, including the liver, subcutaneous loose connective tissues, serosal surface and other tissues and organs. Histologically, proliferative histiocytic cells (PHCs) were scattered in the alveolar cavities, bronchioles and submucosa of bronchioles, with evident cellular and nuclear pleomorphism, and thus the alveolar septa were obliterated. The histopathological changes in other organs included chronic sclerosing glomerulonephritis, proliferated Kupffer cells in the liver, adrenal edema and interstitial connective tissue hyperplasia, as well as atrophy of the small intestines and spleen. Furthermore, immunohistochemical analysis results were strongly positive for CD1a, vimentin, S100 and E-cadherin in the membrane or cytoplasm of PHCs, supporting an LC phenotype. Conclusions: Here, we present a rare pulmonary Langerhans cell histiocytosis case in an African lion.