Erdheim-Chester manifesting purely as a neurological disease: case report

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Case presentation: A 60-year-old male, with a history of hypertension and deep vein thrombosis, presented with vertigo, paraparesis, and dysarthria for three months. On physical examination he had dysarthria, grade 3 hip flexion (bilaterally) and grade 4 plantar flexion and dorsiflexion of the feet, no sensory deficits, truncal cerebellar ataxia, and more pronounced left-side appendicular dysmetria. Magnetic resonance imaging (MRI) showed nodular masses involving the pons, both peduncles and cerebellar hemispheres, and an expansive lesion in the left cerebellar hemisphere, suggesting metastatic neoplasm. A month later, he was submitted to a craniectomy. Pathological findings showed a dense proliferation of histiocytes with abundant cytoplasm, giant Touton cells, and a moderate lymphocytic infiltrate consistent with Erdheim-Chester disease (ECD). On cytogenetic analysis, BRAF V600 mutation-positive tumor status confirmed. Then, vemurafenib therapy was initiated. On the 6-month follow-up, still in immunotherapy, he maintained dyslalia and left hemiparesis. He eats without assistance but does not deambulate. Discussion: We report a case of ECD in a 60-year-old patient with pure neurological signs. ECD is a rare multi-system non-Langerhan cell clonal histiocytosis, with less than 1000 reported cases, that may affect the CNS. The mean age of diagnosis is 57 years with a male prevalence. Its etiology involves activation of the mitogen-activated kinase pathway, leading to tissular accumulation of histiocytes. It is clinically heterogeneous, with bone pain in distal extremities in almost all cases. The most common neurological manifestations are cerebellar and pyramidal syndromes and even though those present in almost 41% of the patients, pure neurological disease is rare, with 39 cases reported. At MRI, the lesions are T2-hyperintense masses affecting mostly the pons, and cerebellum. Classic histological features are foamy histiocytes, multinucleated giant cells, and Touton giant cells. Immunohistochemical staining is positive for CD68 and negative for CD1a. The gold standard for diagnosis is the detection of any MAPK pathway alterations, especially BRAF mutation, that was present in our patient, the treatment for which is BRAF-inhibitors such as vemurafenib. It is important to consider other histiocytic disorders, solid metastatic tumors, or primary central nervous system tumors in the differential diagnosis. In our case, the MRI suggested metastatic lesions, which were later proven a manifestation of the ECD. The prognosis is poor, as there is no known cure, and neurological involvement worsens its outcome. Final comments: ECD is a rare disease that may have only CNS symptoms, which greatly increases mortality. In patients with new-onset cerebellar and pyramidal syndromes with masses in imaging with unclear etiology, ECD should be considered as a differential diagnosis. Correlation of clinical features, histology, and radiological findings is essential.

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