PubMed · 7375786
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J Leibowitch. 1980-03-01. [Complement in human disease: hypocomplementemias].. https://pubmed.ncbi.nlm.nih.gov/7375786/
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The complement system has been shown to play a pathogenic role in only a small number of muscle diseases. A complement-induced microangiopathy is important in dermatomyositis and in the rare disorder, necrotizing myopathy with pipestem capillaries. Recent studies demonstrate the reversibility of microvascular damage in dermatomyositis by intravenous immune globulin which appears to intercept the assembly and deposition of membrane attach complex. In myasthenia gravis, complement-mediated lysis directed at the acetylcholine receptor leads to a cascade of events reducing the number of receptors, simplifying the complex architecture of the junctional folds and decreasing the available surface for the insertion of new receptors. The newest condition in which a role for complement has been demonstrated is X-linked vacuolated myopathy. The condition is of interest because membrane attack complex deposits result in shedding of complement-laden membrane fragments in contrast to a cytolytic process as the consequence of assembly of the terminal complement components.
Deficiencies of individual complement proteins may be accompanied by SLE or related syndromes. Deficiencies of the classic activation pathway are often involved. In cases of C4 and C2 deficiency, there is evidence that this association occurs more frequently than would be expected by chance. The clinical picture differs from classic SLE. There is an increased frequency of skin involvement, a decreased frequency of renal disease, low or absent levels of antibody to native DNA, and increased levels of anti-Ro (SS-A). The mechanism for the association probably involves the effects of C3 and C4 on the precipitation of immune complex solubility, or on their processing through cell surface c4b/c3b receptors on phagocytes. Disseminated or recurrent Neisseria infections are common in patients lacking the constituents of the terminal MAC that are important in killing these organisms.
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.