Erdheim-Chester disease with bilateral orbital masses and multi-systemic symptoms: two case reports

BACKGROUND

Erdheim-Chester disease (ECD) is a rare histiocytic disorder characterized by multisystem xanthogranulomatous infiltration by lipid-laden histiocytes. We report two cases of ECD involving the orbit and describe their clinicopathologic factors, treatments, and prognosis. One was a rare case of ECD complicated with primary thrombocytosis.

CASE PRESENTATION

This study describes two patients with bilateral orbital ECD. Both presented with proptosis and visual loss; imaging findings showed bilateral intraorbital masses. Both had different degrees of systemic symptoms (pleural effusion, pericardial effusion, ascites, and heart failure) before the ocular symptoms and did not find the cause before ophthalmic tumor resection and pathological biopsy. The diagnosis of ECD was confirmed after pathological biopsy and detection of BRAF^V600E mutation. Patient 2 also with primary thrombocytosis and had a CALR mutation as well as the BRAF^V600E mutation. Both patients were recommended to receive targeted therapy. Patient 1 refused targeted therapy for financial reasons and was discharged after local radiotherapy only. The patient had no light perception in either eye and no improvement in systemic symptoms. Patient 2 began targeted treatment after diagnosis and reached the discharge criteria 2 weeks later. He is in good condition at present, but unfortunately, his eyesight has not improved because of the irreversible damage to his visual function.

CONCLUSION

ECD is easily misdiagnosed and missed because of its rarity and diverse clinical manifestations. Orbital involvement is common in ECD, and surgery is the most frequently employed approach. Despite the surgical resection is not curative, its significance lies in biopsy to establish diagnosis and/or surgical debulking to relieve mass effect, minimizing further impairment of visual function. Targeted therapy is the most effective treatment for patients with a positive BRAF mutation gene. Evaluation of a concomitant myeloid neoplasm is also critical before initiating targeted therapies for refractory ECD.

[Elucidated pathogenesis and therapeutic prospects in Langerhans cell histiocytosis]

Langerhans cell histiocytosis (LCH) is characterized by immature dendritic cell proliferation, which is currently classified as an inflammatory myeloid neoplasm. Clinical features and outcomes vary from spontaneously regressing isolated bone disease to fatal liver, spleen, or hematopoietic system (risk organ) involvement-positive multisystem disease. LCH cells have the only mutation in the mitogen-activated protein kinase (MAPK) signaling pathway gene, represented by the BRAF V600E mutation, which is the driver mutation. The type of disease depends on the stage of hematopoietic cell differentiation at which the mutation occurs. LCH cells acquire anti-apoptosis and senescence-associated secretory phenotype by oncogene-induced senescence, with migration failure to lymph nodes. These cause LCH cell accumulation and various inflammatory cell recruitment in the lesion, resulting in severe inflammation. Tissue damage in LCH is due to this inflammation, not the LCH cell proliferation. Patients with a risk of organ involvement without the initial treatment response may be rescued by allogeneic hematopoietic stem cell transplantation after reducing the disease activity with MAPK inhibitors. Intravenous zoledronic acid and intrathecal cytarabine injections have been introduced into the ongoing clinical trial in Japan to reduce bone recurrence and prevent neurodegeneration as sequelae.