[Neuropathies associated with monoclonal IgM anti-MAG antibodies]. / Neuropathies associées à une IgM monoclonale anti-MAG.

Monoclonal IgM anti-MAG associated peripheral neuropathies are part of demyelinating dysimmune peripheral neuropathies. The hematological disease probably does not influence the outcome of the neuropathy. Neuropathies associated with IgM anti-MAG antibodies are predominantly sensory and distal polyneuropathies associated with ataxia, unsteadiness and tremor. The neurophysiological features include a symmetric sensorimotor demyelinating neuropathy with more slowing of conduction in the distal than in the proximal nerve segments, a length-dependence, and a variable degree of denervation. High titers of IgM anti-MAG antibodies confirm the diagnosis. The natural history is mostly slow with mild to moderate functional impairment. However, some patients have a faster evolution associated with a more severe handicap. Immunotherapies studies have failed to demonstrate significant efficacy of these treatments. Furthermore, severe adverse effects are not uncommon with any of these therapies. Thus, the risk of possible severe adverse effects must be balanced against any possible benefits. More research is needed to improve the management of anti-MAG neuropathies: research on treatment, on prognostic factors, and development of specific assessment scales adapted to the particularities of anti-MAG neuropathies.

Two cases of disseminated Mycobacterium avium infection associated with a new immunodeficiency syndrome related to CXCR4 dysfunctions.

Disseminated Mycobacterium avium complex (MAC) infection is a rare but severe disease mostly seen in patients with AIDS. It has been previously described in patients suffering from other kinds of immunodeficiency (e.g. primary immunodeficiency diseases in children or hairy cell leukaemia). We report two cases of disseminated MAC disease in young women with extended granulomatosis that revealed a new form of severe immunodeficiency syndrome. Both clinical observations initially appeared to be very similar to WHIM syndrome (Warts, Hypogammaglobulinemia, Infection, Myelokathexis), a rare immunodeficiency disease correlated with CXC chemokine receptor 4 (CXCR4) mutation leading to an impaired internalization of the receptor upon its ligand CXCL12. We investigated the CXCR4 status of the lymphocytes in both patients and found a severe defect in CXCL12-promoted internalization but no mutation of its gene. Moreover, myelokathexis was not noted in bone marrow biopsies and therefore a diagnosis of WHIM syndrome could not be assessed. This immunodeficiency syndrome associated with CXCR4 dysfunction was responsible for severe MAC infection in our patients, with a fatal outcome in one case. It may be possible that these patients would have benefited from early antimycobacterial infection or azythromycin prophylaxis.