Teaching Case

A 43-year-old male patient was admitted in our hospital for palpitations, cervical pain and dyspnoea. The patient complained of several transient episodes of disorientation in the last two months. Also, the patient reported myoclonus, intrusive thoughts and the symptoms of central diabetes insipidus as polyuria and polydipsia.

The brain CT described multiple hypodense lesions localized in the pons, which show a diffuse and inhomogeneous contrast enhancement. The orbits were occupied by hypodense, bilateral, pseudotumoral masses, with intraconal extension. The same lesions displaced the extrinsic muscle and the optic nerves. After the injection of contrast medium, the orbital masses showed a homogenous and rapid enhancement (Fig. 1).

For a better definition of brain involvement, we performed also the brain MRI, which showed multiple areas of high intensity signal in T2 sequences, localized in the hippocampus, parahippocampal gyri, pons and middle cerebellar peduncoles. The lesions infiltrated also the hypothalamus with extension to tuber cinereum. All of these lesions enhanced after the injection of gadolinium (Fig. 2). The brain MRI confirmed the presence of bilateral pseudotumoral masses in the orbits, which appeared hypointense in T1 and T2 sequences with homogeneous contrast enhancement (Fig. 3).

Erdheim-Chester disease (ECD) is a rare non-Langherans cell histiocytosis, first described in 1930. The disease is characterized by the infiltration of tissues by foamy non Langerhans-cell histiocytes CD68+, CD1a-, S-100-, with middle aged male predominance [1].
The most common site of involvement is the distal diaphysis of long bones, in particular the femurs [2]. However, the disease may infiltrate the retroperitoneum, the lungs, the cardiovascular system and the central nervous system [3].

The brain infiltration occurs in about 40% of patients. The most frequent intracranial site involved is the hypothalamic-pituitary axis. The MRI is the modality of choice to identify hypothalamic and pituitary lesions. They appear hyperintense in T2 sequences and enhance after the injection of gadolinium. The hyperintensity of the posterior pituitary lobe on T1 sequences may be absent. The pituitary involvement may cause the central diabetes insipidus, frequently seen in Erdheim-Chester disease [4].
Other intracranial parenchymal lesions occur more frequently in the infratentorial region. They are hypodense at CT and hyperintense in T2 sequences at MRI, with variable enhancement and localizations. They may occur in the brainstem, cerebellum, hippocampus, mammillary bodies, fornix, cerebellar peduncles and parahippocampal gyri [5]. The supratentorial infiltration is less commonly observed [1]. The clinical manifestations are dependent on the anatomical localization of the lesions and the cerebellar ataxia and the pyramidal signs are the most frequent symptoms [4]. The meningeal lesions are sometimes observed and are often single or multiple dural meningioma-like masses or stellate formations [4-6]. The spinal cord lesions are very rare [7].
About 30-40% of patients with Erdheim-Chester disease have orbital involvement, which may cause exophthalmos. The orbital lesions are usually bilateral, intraconal xanthogranulomatosus pseudotumours, but unilateral masses are also reported. At MRI, they appear hypointense in T1 and T2 sequences with homogeneous enhancement after injection of gadolinium [8].

In our case, along the neuroradiological evaluation, we performed also a thoraco-abdominal CT study, which showed the involvement of cardiovascular system, lungs and the presence of retroperitoneal fibrosis. These features and the brain infiltration direct us towards the diagnosis of a systemic infiltrative disease, like Erdheim-Chester disease. To support this hypothesis, we performed also the bone scintigraphy, which demonstrated the infiltration of the distal right femur. However, we performed a CT guided biopsy of retroperitoneal mass and the histological proofs showed the tissue infiltration by non-Langerhans cell histiocytes. This finding confirmed the diagnosis of Erdheim-Chester disease.
The patient was treated with steroids and interferon alpha with a good clinical response.