[Diffuse normolipidemic plane xanthomatosis and monoclonal dysglobulinemia. A case with anti-lipoprotein activity of monoclonal immunoglobulin and hypocomplementemia].

INTRODUCTION

Diffuse normolipaemic plane xanthomatosis associated with monoclonal dysglobulinaemia has been recognized as a clinical entity for more than 30 years. Antilipoprotein activity has been reported in certain cases with monoclonal immunoglobulinaemia or hypocomplementaemia.

CASE REPORT

A 64-year-old woman developed simultaneously diffuse normolipaemic plane xanthomatosis and monoclonal IgG kappa dysglobulinaemia. This paraprotein was initially associated with monoclonal gammapathy of undetermined signification (called "benign") before evolving into a myeloma. This aggravation was associated with an expansion of the skin lesions. Immunological exploration demonstrated the presence of IgG-lipoprotein complexes in the plasma and hypocomplementaemia suggesting incomplete activation of the classical pathway (low CH50 and fraction C4).

DISCUSSION

According to the literature, the most probable hypothesis for the pathogenesis of the xanthomatosis-dysglobulinaemia association is a specific interaction between the monoclonal immunoglobulin and lipoprotein metabolism. In normolipaemic forms, the immunoglobulin-lipoprotein complexes are recognized by "waste-receptors" and accumulate in the dermal macrophages while the mechanism of lipoprotein captation in the other types of cells remains normal, explaining the absence of hyperlipidaemia.