Chinese Erdheim-Chester disease: clinical-pathology-PET/CT updates

Erdheim-Chester disease (ECD), one type of systemic non-Langerhans cell histiocytosis, has been rarely seen and is characterized by the accumulation of foamy CD68+CD1a- histiocytes. We reported a case of ECD and reviewed the clinical features of 13 cases of ECD reported so far in China. A 53-year-old male was diagnosed with central diabetes insipidus in March 2014, followed by fever, splenomegaly and anemia in July 2014. His initial pituitary magnetic resonance imaging (MRI) revealed the absence of high signal at T1-weighted image in posterior pituitary without any lesion. A further positron emission tomography/computer tomography (PET/CT) images showed elevated metabolic activity of (18)F-2-fluro-D-deoxy-glucose (FDG) and low (13)N-NH3 uptake in the posterior pituitary, and multi-organ involvement. Biopsy at right femur lesion revealed that granulomatous infiltration of foamy histiocytes and Touton giant cells surrounded by fibrosis tissues. Immunohistochemistry stain was positive for CD68, negative for CD207/Langerin and S-100. The diagnosis of ECD was confirmed and the treatment with pegylated interferon was effective. ECD was a possible immune-related disorder concluding from the IgG4 immunohistochemistry results. We summarized the pathological manifestations for ECD and its differential diagnosis from Langerhans cell histiocytosis (LCH) and Rosai-Dorfman disease (RDD). ECD should be considered by both pathologists and clinicians in the differential diagnosis when central diabetes insipidus is accompanied with multi-organ involvement, especially skeletal system involvement, or recurrent fever. LEARNING POINTS: ECD should be considered when central diabetes insipidus is accompanied with multisystem involvement, especially symmetric/asymmetric bone lesions, or recurrent fever. PET/CT scanning was helpful for locating pituitary lesion, discovering multiple system involvement and indicating the biopsy sites. Conducting proper immunohistochemistry stains was important for diagnosing ECD. ECD might be correlated with immune disorder.