Teaching Case

A 46-year-old female patient with a history of diabetes insipidus suspicious for hypophysitis in 2008, complained about overall fatigue, night sweats and muscle aches. Laboratory evaluation revealed a mild leukocytosis and increased erythrocyte sedimentation rate.

Initial MR imaging in 2008 showed an enhancing mass of the pituitary stalk (Fig. 1) with a differential diagnosis of hypophysitis, lymphoma, histiocytosis, neurosarcoid and germinoma. Additional contrast-enhanced CT of the chest and abdomen to look for other signs of lymphoma or sarcoid was unremarkable.

Abdominal ultrasound in 2016 demonstrated bilateral perirenal fluid and dilatation of the renal pelvis. Additional CT of the chest and abdomen revealed the presence of pericardial effusion, circumferential infiltration of the thoracic aorta and its main branches (Fig. 2), symmetric soft-tissue infiltration of the perirenal fat, with the presence of “hairy” kidneys, and bilateral adrenal enlargement (Fig 3.).
Because diagnosis of Erdheim-Chester disease was suspected, X-rays of the extremities (Fig. 4a), bone scan (Fig. 4b) and MRI of the orbits (Fig. 5) and the heart (Fig. 6) where made, which all revealed abnormalities compatible with Erdheim-Chester disease.

Erdheim-Chester disease (ECD) is a rare form of non–Langerhans cell histiocytosis of unknown origin affecting mainly patients of middle age. It has a slight male predominance. Histologically there is a mixture of tissue infiltration by foamy histiocytes and fibrosis. It is a multisystemic disease and takes an indolent clinical course in some patients and a life-threatening course in others.

Patients may present with general symptoms like fever and weight loss. The most common clinical manifestations are mild bone pain, diabetes insipidus, bilateral exophthalmos and xanthelasmata. Other symptoms depend on organs involved including neurological symptoms, involvement of the cardiovascular system, dyspnoea, and retroperitoneal fibrosis with perirenal and/or ureteral obstruction.

Image characteristics:
- Bones: Symmetric osteosclerosis of the diaphysis and metaphysis of the long bones on X-rays with increased tracer uptake in the lesions on bone scintigraphy. [2]
- Meningeal lesions and multiple enhancing intra-axial masses, best seen on MRI. The location and size of the lesion determine the symptoms. [1]
- Hypothalamic-Pituitary Axis: nodular infundibular stalk mass or absent pituitary bright spot on T1 weighted MR images. [1]
- Orbits: Uni- or bilateral enhancing intraconal masses (30%). [1]
- Lungs: Ground-glass opacities, smooth interlobular septal thickening, centrilobular nodular opacities and pleural thickening or effusions [3].
- Cardiovascular: The most frequent manifestation is periaortic fibrosis with smooth circumferential infiltration of the thoracic and abdominal aorta (“coated aorta”). It frequently spreads around the main aortic branches and can cause renovascular hypertension. Other abnormalities include infiltration of the right heart, which can appear as a pseudo-mass, and pericardial thickening or effusions. [4, 5].
- Renal and perirenal involvement: symmetric, perirenal tissue infiltration that encases the kidneys (“hairy kidney”). In some cases, extension to the renal hilum and proximal ureters causes hydronephrosis. [4, 6] Infiltration may extend upward to the adrenal fossae with associated adrenal hypertrophy.

Diagnosis is usually based on the characteristic histological findings and skeletal abnormalities on X-rays or bone scintigraphy. [5] Because of the low frequency and the broad spectrum of clinical manifestations of this disease, it is easily misdiagnosed. The presence of bone pain and diabetes insipidus, along with characteristic abnormalities on imaging, should raise suspicion for ECD.

In the past treatment options included steroids, radiotherapy, chemotherapy and surgery but none of these treatments showed to improve survival with a mean survival after diagnosis of 19.2 months. In recent years there has been progress with the use of interferon-a and BRAF inhibition with a five-year survival of 68%. [5, 7]