Histiocytosis is a set of distinct proliferative illnesses defined by the proliferation and infiltration of varied numbers of dendritic cells, macrophages, and monocytes in the afflicted tissues. The skin and other organs may be impacted by the inflammatory infiltration. It can occur at any age. The severity of the symptoms can range from mild to severe, depending on the degree and type of organ involvement. Although certain forms of histiocytosis can be fatal, others can be treated successfully without sequelae. Langerhans cell histiocytosis manifests itself clinically in both children and adults. A combination of clinical, histological, and radiological tests is required to achieve a diagnosis. A severe, multisystemic, acute form of Langerhans cell histiocytosis is called Letterer-Siewe illness, which usually affects infants in their first year of life. In this article, we provide a brief literature review and a case study of a 9-month-old girl who presented with recurring gastrointestinal problems as the first sign of Letterer-Siwe disease.