Castleman disease (CD) is a rare lymphoproliferative disease that is clinically classified into unicentric Castleman disease (UCD) and multicentric Castleman disease (MCD). According to the status of human herpes virus-8 (HHV-8) infection, MCD is further classified into HHV-8-positive MCD, and HHV-8-negative MCD, which is also called idiopathic multicentric Castleman disease (iMCD). There are standard treatment options for both UCD and HHV-8-positive MCD, but there has been no uniform standard of diagnosis and treatment for iMCD, which mainly relied on the experience of clinicians. In recent years, Castleman Disease Collaborative Network (CDCN) has newly defined the concept and diagnostic criteria of iMCD, and a comprehensive guidance on the treatment of iMCD was established in November 2018. In this paper, we try to review the current treatment options and advances of iMCD, which might help Chinese clinicians to diagnose and treat this rare disease.

Objective: To improve the understanding of rare anti-myelin-associated glycoprotein (MAG) positive IgM monoclonal gammopathy related peripheral neuropathy (IgM-PN) . Methods: Eleven cases of IgM paraproteinemia and anti-MAG antibody positive neuropathy diagnosed since 2014 in Peking Medical Union College Hospital were summarized. The medical records including clinical manifestation, lab results, treatment and prognosis were analyzed. Results: Among the 11 patients (8 male and 3 female) , the median onset age is 63 years old (range from 52 to 77 years old) . The peripheral neuropathy of 9 patients were characterized by distal onset of numbness, 6 patients suffered from muscle weakness. The nerve conduction velocity study indicated that all 11 patients had demyelinating peripheral nerve damage, which was sensory predominant and more severe in lower limbs, 6 of them had secondary axonal damage. Monoclonal IgM gammopathy was identified in all 11 patients, among which 6 were IgM κ, 2 IgG κ and IgM κ bi-clonal, 3 IgM λ. Three patients were diagnosed with Waldenström’s macroglobulinaemia. The anti-MAG-IgM antibody was positive in all 11 cases. After diagnosis, 9 patients received combination chemotherapy including rituximab or rituximab treatment alone. The monoclonal IgM level declined significantly in 7 patients. The neuropathy was stable or improved. Conclusions Anti-MAG antibody positive IgM-PN is a rare M protein related disease. In peripheral neuropathy with undetermined etiology, we suggest to screen M protein and anti-MAG antibody. Chemotherapy including rituximab or rituximab alone is recommended as first-line therapy.