[Histiocytoses: General classification and molecular criteria]

Bone Marrow Infiltration in Rosai-Dorfman Disease

Rosai-Dorfman disease (RDD) is a rare and benign nonLangerhans cell histiocytosis. RDD commonly affects children and young adults typically presenting with massive, painless, and bilateral cervical lymphadenopathy. Extranodal involvement is present in about 40% of cases, and bone marrow infiltration is rare and unusual. RDD prognosis is usually good, however, involvement of bone marrow is associated with poor prognosis. We report a case of RDD with bone marrow involvement occurring in a 5-year-old female. She was admitted for asthenia, gingival bleeding, and diffuse bone pain without fever. Physical examination showed pallor, petechiae over the abdomen, painless and bilateral cervical lymphadenopathy, and several bony nodules, without splenomegaly or hepatomegaly. Cell blood count revealed microcytic hypochromic anemia with thrombocytopenia. Bone marrow aspiration showed infiltration by large histiocytes with hypochromatic nuclei and abundant vacuolated cytoplasm without emperipolesis. Biopsies of bone marrow, lymph node, and bone revealed immunohistochemical features of RDD: the histiocytes were positive for CD68 and S100 protein, but negative for CD1a. The patient initially received symptomatic treatment. One week after admission, she died of septic shock before the final establishment of RDD diagnosis. This case report highlights that bone marrow involvement in RDD is rare and associated with poor prognosis. We also aim to emphasize the obligation of bone marrow exploration in patients with RDD and presenting cytopenias in order to make an early diagnosis of bone marrow infiltration.

Juvenile xanthogranulomas in Asian children

Juvenile xanthogranuloma (JXG) is the most common non-Langerhans cell histiocytic disorder. It can rarely be associated with systemic involvement. There is a paucity of literature on JXG in Asian children. We aim to describe the epidemiology, clinical features, systemic associations, histological features and outcome of a cohort of Asian children with JXG, and review the literature on the condition. We retrospectively reviewed the demographic, clinical and histological data of patients less than 16 years of age, diagnosed with JXG at our tertiary pediatric hospital between January 2002 and April 2019. A total of 147 children with JXG were identified, with a slight male preponderance of 53.1%. The median age of the onset was 15.5 months, with 69.4% presenting before 2 years of age. There was no racial predilection. The most frequently involved site was the head and neck region (44.2%). The majority of patients (76.2%) presented with a solitary lesion. Spontaneous resolution was documented in 57.7% of our patients with mean duration to resolution of 18.8 months. The proportion and speed of resolution did not differ in children with single or multiple lesions. No ophthalmologic complications were detected in our study cohort. JXG in children is generally limited to the skin and is rarely associated with systemic involvement, including the eye. Unless clinically indicated, the results from our study does not support routine screening for juvenile myelomonocytic leukemia, eye or systemic complications, even in the setting of multiple cutaneous JXGs.

[Erdheim-Chester disease presenting with bilateral orbital involvement: Report of three cases]

PURPOSE

To report treatment outcomes of orbital tumors associated with Erdheim-Chester disease and to highlight the importance of systemic work-up in patients presenting with bilateral proptosis.

PATIENTS AND METHODS

Three patients with Erdheim-Chester disease, whose initial manifestation was bilateral proptosis, were retrospectively studied. The course of onset, clinical, imaging and histopathological features, systemic associations and response to treatment were reviewed. The main outcome measures were Hertel measurements and orbital tumor regression on imaging studies.

RESULTS

All patients presented with bilateral non-pulsatile proptosis resistant to retropulsion and headeache without specific localization. Magnetic resonance imaging studies showed bilateral intraconal orbital tumors. Incisional biopsy of these tumors demonstrated CD68+, CD1a-, and S100- histiocytic infiltrates consistent with the diagnosis of Erdheim-Chester disease. The BRAFV600E mutation was found in all cases. Systemic work-up revealed asymptomatic bony involvement in the lower extremities, perirenal fibrosis, central nervous system and cardiac involvement. All patients initially received pegylated interferon-α2a, which resulted in excellent responses except for the orbital tumors. Two patients were then treated with vemurafenib, which resulted in rapid regression of the orbital lesions.

CONCLUSION

Pegylated interferon-α was highly effective in the control of cardiac, perirenal, skeletal and cerebral involvement but not the orbital tumors. The infiltrative orbital lesions of Erdheim-Chester disease would appear more responsive to vemurafenib.