IgG Subclasses: Relationship to Clinical Aspects of Multiple Myeloma and Frequency Distribution among M‐Components

Abstract

The possible role of IgG subclasses in patients with M‐components or multiple myeloma was investigated. Among 900 patients with monoclonal proteins, the following IgG subclasses were identified: 77 % were IgG 1 ; 14 % were IgG 2 ; 6 % were IgG 3 ; and 3 % were IgG 4 . The IgG of normal sera consists of 64–70 % IgG 1 , 23–28 % IgG 2 , 4–7 % IgG 3 and 3–4 % IgG 4 . IgG 1 M‐components were seen more frequently and IgG 2 less frequently than had been expected. There were 389 patients with documented multiple myeloma assigned to four subgroups based upon IgG sub‐classification of their M‐components. These four groups resembled each other in many respects, but patients with IgG 2 myeloma tended to develop hypercalcaemia and anaemia more frequently than patients with IgG 1 or IgG 4 myeloma; patients with IgG 3 myeloma tended to develop anaemia and had azotaemia more frequently than patients with IgG 1 or IgG 4 myeloma.