More than Just Langerhans Cell Histiocytosis: A Radiologic Review of Histiocytic Disorders

Abstract

Although Langerhans cell histiocytosis (LCH) is a familiar entity to most radiologists and to pediatric radiologists in particular, it is but one of a group of disorders caused by the overproduction of histiocytes, a subtype of white blood cells. Other less familiar diseases in this category are Erdheim-Chester disease (ECD), juvenile xanthogranuloma (JXG), Rosai-Dorfman disease (RDD), and hemophagocytic lymphohistiocytosis (HLH). This review describes the classification system, clinical manifestations, and pathophysiology of each disease, with particular attention to differential radiographic findings, including typical locations of involvement and varying appearances at radiography, computed tomography, magnetic resonance imaging, ultrasonography, and nuclear medicine imaging. Although LCH has a wide variety of manifestations and appearances, classic imaging findings include vertebra plana, skull lesions with a beveled edge, the "floating tooth" sign, bizarre lung cysts, and an absent posterior pituitary bright spot with infundibular thickening. The classic imaging findings of ECD are a perirenal rind of soft tissue and patchy long bone osteosclerosis. RDD has more nonspecific imaging findings, including lymphadenopathy (most commonly cervical) and intracranial lesions. Imaging findings in HLH are broad, with the most common abnormalities being hepatosplenomegaly, cerebral volume loss, and periventricular white matter abnormalities. JXG can manifest at imaging, but radiology does not play a major role in diagnosis. Familiarity with these disorders and their associated imaging findings facilitates correct and timely diagnosis. Imaging also features prominently in the assessment of treatment response.

Review of Rosai-Dorfman Disease: New Insights into the Pathogenesis of This Rare Disorder

“…A reversal in peripheral CD4:CD8 ratio has also been observed [6]. Imaging manifestations of RDD are also nonspecific [7], but FDG-PET/CT can be used to evaluate the exact extent of dissemination [8]. …”

Cardiothoracic manifestations of primary histiocytoses

“…5 In the past, various nomenclatures were used to describe the various patterns of disease encountered including histiocytosis X, eosinophilic granuloma, Letterer-Siwe disease and Hand-Schüller-Christian disease; however, these terms are now considered obsolete. 6 Systemic LCH is divided into three different disease forms based on the number of lesions and systems affected. 6,7 Unifocal LCH is the most common manifestation (70% of cases), almost exclusively involves the skeletal structures and can be either monostotic or polyostotic.…”

“…6 Systemic LCH is divided into three different disease forms based on the number of lesions and systems affected. 6,7 Unifocal LCH is the most common manifestation (70% of cases), almost exclusively involves the skeletal structures and can be either monostotic or polyostotic. The lungs may also occasionally be affected.…”

“…The diagnosis of systemic LCH is based on clinical, histopathologic, radiologic and immunohistochemical data. 6 In the lungs, multiple small nodules with early signs of cavitation and thin-walled air cysts (,10 mm) are the primary findings (Figure 1). Spontaneous pneumothorax may occur in cases of ruptured peripheral cysts.…”

“…In the chest, ribs are frequently involved, particularly in adults. 6,11 The vertebral bodies are also commonly affected. 11 Uniform collapse of the vertebral body with preservation of the intervertebral disc space has been termed vertebra plana or Calve disease ( Figure 2).…”