Biopsy-Documented Myopathy and Vasculitis in Essential Mixed Cryoglobulinemia

A skeletal muscle involvement associated with skin, renal and liver pathology has been described in patients with essential mixed cryoglobulinemia. In some cases the muscle atrophy was consequence of a peripheral neuropathy but in such patients the muscle pathology has not been defined. Skin and skeletal muscle biopsies were performed in 6 patients with type II essential mixed cryoglobylinemia. They showed skeletal muscle weakness and atrophy and slight increase of CPK. Two patients showed clinical signs of peripheral neuropathy. Morphological studies revealed vasculitis and lymphoid perivascular infiltration in the skin and fascia! connective tissues. Vasculitis, perivascular lymphoid infiltration and muscle fibre necrosis were seen in all cases. Immunofluorescence showed IgM and IgG components and complement fractions in the arteriolar and capillary walls. At immunophenotyping, mononuclear T cells expressing CD4 and CDS antigen were intermingled with few polytypic B cells. This study suggest that necrotizing changes in skeletal muscle of patients with type II mixed cryoglobulinemia result from a cryoglobulin-mediated vasculitis and/or intravascular precipitation of cryoglobulins with consequent ischaemic changes on muscle fibres. These alterations may be overimposed on denervation atrophy seen in patients with documented peripheral neuropathy.