Teaching Case

A 44-year-old man with no known comorbidities presented with bilateral lower limb oedema and right-sided proptosis associated with decreased vision for the last year. Loss of appetite and weight loss were present for three months. On examination, he had ascites. Laboratory tests showed no remarkable findings

Xanthelasma of right eyelid noted (Figure 1). Orbit-MRI revealed heterogeneously enhancing T2WI-hypointense soft-tissue thickening involving bilateral extraocular muscles, intraconal spaces with right-sided proptosis and compression of bilateral optic nerves (Figures 2a, 2b). Axial post-contrast T1WI image showed an enhancing focus in left peridentate nucleus region (Figure 2b) and enhancing thickening involving bilateral tentorium cerebelli (Figure 2c). Optic disc drusens were noted in both eyes (Figures 3a, 3b). Axial-CT demonstrated sclerotic bone thickening of bilateral ethmoidal and sphenoidal sinuses (Figure 3a). T2WI-hypointense soft-tissue and wall thickening of paranasal sinuses (Figures 4a, 4c) showed heterogeneous post-contrast enhancement (Figures 4b, 4d). T2WI-hypointense lobulated lesion (Figure 5a) with increased FDG-uptake (Figure 5b) involving choroid plexus in right occipital horn showing homogenous post-contrast enhancement (Figure 5c) was noted. Sagittal non-contrast T1WI image demonstrated absence of posterior pituitary bright spot (Figure 6). USG-neck showed perivascular thickening in right carotid bulb (Figure 7). Cardiac-MRI showed soft-tissue thickening involving walls of both atria, atrioventricular groove, right coronary artery and left circumflex artery (Figure 8a), showing late gadolinium enhancement (Figure 8b). FDG-avid diffuse retroperitoneal soft-tissue thickening encasing kidneys and bilateral moderate hydroureteronephrosis (Figures 9a, 9b) was noted. Intense FDG-uptake was observed in bilateral testis (Figure 10). Radiographs of bilateral knee joints demonstrated FDG-avid symmetrical metadiaphyseal osteosclerosis (Figures 11a, 11b).

Erdheim-Chester Disease (ECD) is a multisystemic non-Langerhans cell histiocytic disorder seen in adults between 40 and 70 years [1], which manifests with diverse clinical symptoms like bone pain (most common) [2], exophthalmos, xanthomas, cerebellar signs, dyspnoea, diabetes insipidus and constitutional symptoms [3], posing a diagnostic dilemma for clinicians. Our case illustrates various imaging manifestations in all organ systems. Pathognomic features of skeletal involvement include bilateral symmetric-metadiaphyseal osteosclerosis, cortical thickening, and increased FDG-uptake in long bones, predominantly lower limbs, sparing epiphysis and axial skeleton [4,5]. Patients with neurologic involvement carry a poor prognosis and are an independent predictor of death [3,6]. The absence of high signal intensity of posterior pituitary on non-contrast sagittal T1W-image [7] was observed in our case. Meningeal lesions [8], bilateral symmetric T2-hyperintense lesions in the dentate and cerebellar hemisphere with no post-contrast enhancement [8,9] and involvement of choroid plexus of lateral ventricles [10] have been described in ECD. Increased meningeal enhancement and thickening in bilateral tentorium cerebelli, basitemporal region, along cavernous sinus and an asymmetric enhancing focus in the left peridentate nucleus along with T2WI hypointense lobulated lesion with increased FDG-uptake showing homogenous post-contrast enhancement involving choroid plexus of right occipital horn were noted in our case. Orbital involvement occurs in the form of bilateral enhancing intraconal/extraconal masses with/without optic nerve compression [11]. Paranasal sinus involvement occurs in the form of sinus wall osteosclerosis [8] and FDG-avid heterogeneously enhancing soft-tissue thickening [5]. Bilateral optic-drusens, as noted in our case, have been reported very rarely [3]. Cardiovascular involvement carries a poor prognosis, and it can manifest as pericardial infiltration, myocardial infiltration of the atrioventricular wall, atrial (predominantly right), interatrial septum with late gadolinium enhancement [12] and increased FDG-uptake. This was demonstrated in our case using cardiac-MRI. Vascular involvement, described in previous studies as form of periadventitial soft-tissue infiltration of the aorta, predominantly infra-renal abdominal aorta, bilateral common carotid arteries, subclavian arteries, pulmonary trunk and visceral arteries, predominantly renal artery [13], was also noted in our case. Pulmonary manifestations like nodules and interlobular septal thickening [14], as described in previous cases, were not seen in our case. Our study revealed only subsegmental atelectatic bands and pleural effusion as pleuropulmonary manifestations. Retroperitoneal involvement occurs in the form of bilateral symmetric perirenal and pararenal infiltration, resulting in the ‘hairy kidney sign’ and involvement of the proximal ureter [12]. Increased FDG-uptake noted in bilateral testis is very rare in ECD [15]. The final diagnosis of ECD was made based on a biopsy from upper tibial lesion with immunohistochemistry (CD68-positive and CD1a-negative) and a positive BRAF^V600E mutation [1]. The patient was treated with steroids and vinblastine, but unfortunately, the patient succumbed to sepsis after starting treatment.

All patient data have been completely anonymised throughout the entire manuscript and related files.