Radiological manifestations
On standard radiographs, Langerhans cell histiocytosis demonstrates a dynamic pattern. In adult patients, the pathology most commonly affects flat bones.
Key radiological patterns:
- Appearance of lytic lesions (e.g., in the region of the distal humerus).
- Formation of the endosteal scalloping phenomenon (endosteal scalloping), where the lesion "erodes" the inner contour of the cortical layer.
- Variable outcomes: over time, lesions may undergo sclerosis or completely resolve (disappear).
MRI presentation of active lesions
Magnetic resonance imaging allows for a detailed assessment of the bone marrow and surrounding tissues. Lesions in histiocytosis typically have indistinct margins.
| Scanning sequence | Signal characteristics |
|---|---|
| T1-weighted imaging | Intermediate intensity |
| T2-weighted images and STIR | Hyperintense signal |
| With contrast enhancement | Active contrast uptake |
It is important to note that active lesions are always accompanied by pronounced reactive changes: bone marrow edema, adjacent soft tissue edema, and periostitis (often found in the diaphyses, e.g., of the fibula). At the same time, destruction of the cortical layer itself and the extension of a massive soft-tissue component beyond the bone are described extremely rarely.
Erdheim-Chester disease
Erdheim-Chester disease is a rare form of histiocytosis, manifesting predominantly in adulthood (on average at 55–60 years of age). The pathology has a pronounced systemic nature:
- Skeleton: involvement occurs in more than 95% of cases.
- Cardiovascular system: involved in half of patients (50%).
- Retroperitoneal space: development of retroperitoneal fibrosis is observed in approximately 30% of cases.
- Head and CNS: diabetes insipidus, exophthalmos, and other CNS lesions are recorded in 20–30% of patients.
Radiological semiotics of Erdheim-Chester disease
Unlike Langerhans cell histiocytosis, this form has its own strict diagnostic criteria.
- Radiography: bilateral and strictly symmetric sclerosis (cortical and medullary) is revealed. Typical localization is the metadiaphyses of large long tubular bones. The most specific sign is epiphyseal sparing (epiphyseal sparing).
- MRI: T1-weighted images show heterogeneous signal intensity reduction from the bone marrow, while on T2-weighted images and STIR, the signal remains variable.
- Radionuclide methods: bone scintigraphy and PET-CT show high specificity, demonstrating pathologically increased radiopharmaceutical uptake in the affected areas.
Briefly: answers to topical questions
Which skeletal bones are most frequently affected in Langerhans cell histiocytosis in children?
In Langerhans cell histiocytosis, the cranial bones, mandible, ribs, pelvic bones, femur, and vertebrae are affected. For solitary lesions (eosinophilic granuloma), the favored localization is flat bones: the skull, mandible, ribs, and pelvic bones. A classic manifestation of spinal involvement is vertebra plana (vertebra plana). Radiolucent lesions may be detected in the cranial bones and femur.
What changes in the lungs are detected in Langerhans cell histiocytosis on high-resolution CT?
On high-resolution CT, Langerhans cell histiocytosis reveals nodules, cysts, and reticular opacities predominating in the upper lung lobes.
- Nodules (Nodules) — ranging in size from a few millimeters to 2 cm, of subsolid and solid density.
- Cysts — thin-walled, often bizarrely shaped, formed as a result of natural cavitation of nodules.
- Reticular opacities — appear in later stages against the background of cystic changes as a sign of concurrent pulmonary fibrosis.
Polymorphism is characteristic — the simultaneous coexistence of various types of nodules and cysts.
What classic clinical syndromes and forms of Langerhans cell histiocytosis are distinguished in medicine?
In medicine, localized and multifocal forms of Langerhans cell histiocytosis are distinguished, as well as classic clinical syndromes.
- Localized form — involvement of one or several bones.
- Multifocal form — bone involvement combined with extraskeletal manifestations.
- Eosinophilic granuloma (Eosinophilic granuloma) — solitary bone lesions.
- Hand-Schüller-Christian syndrome — a storage disease manifested by the Christian triad (cranial bone defects, exophthalmos, diabetes insipidus), as well as involvement of the skeleton, endocrine system, internal organs, skin, and oral cavity.
Class and exam questions
Which imaging modality is prioritized for detecting multiple lesions?
For a qualitative assessment of multifocal involvement, it is recommended to use whole-body MRI, which in modern practice should replace traditional scintigraphy.
Is Langerhans cell histiocytosis accompanied by destruction of the cortical layer?
Cortical destruction and the formation of a pronounced soft-tissue component are rare and infrequently described in this pathology. Endosteal scalloping is observed more frequently.
What is the main radiological difference of Erdheim-Chester disease in tubular bones?
A key specific sign is epiphyseal sparing (epiphyseal sparing) against the background of symmetric bilateral metaphyseal-diaphyseal sclerosis.
What else to study on this topic
- Pathophysiology of endosteal scalloping development in lytic processes
- Whole-body MRI scanning protocols for detecting multifocal lesions
- Differential diagnosis of retroperitoneal fibrosis
- The link between CNS involvement and the development of diabetes insipidus in histiocytoses
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