Plasma Cell Dyscrasia Associated With the Production of Incomplete (? Deleted) IgG_λ Molecules, Gamma Heavy Chains, and Free Lambda Chains Containing Carbohydrate: Description of the First Case

The clinical, hematologic, and immunoglobulin features of a new form of plasma cell dyscrasia (deleted H and L chain disease) are described. The clinical manifestations are periodic fever and weakness, lymphadenopathy, and hepatosplenomegaly. The hematologic abnormalities are anemia, leukopenia, lymphocytosis, thrombocytopenia, and increased plasma cells in lymph nodes and bone marrow. The protein abnormalities have been identified as (1) monoclonal IgG₁λ A serum globulin (5-6 g/100 ml) with deletions in both H and L chains and an estimated mol wt of 110,000; (2) free γ Fc fragment in serum and urine; (3) urinary excretion (10-20 g/day) of deleted λ-chains (Uλ) with an estimated mol wt of 15,000. Uλ and the λL chains of the IgG are apparently identical. Uλ was shown to contain approximately 26 moles of carbohydrate, with an average of 2.2 moles of sialic acid per 15,000 mol wt. Uλ displayed marked electrophoretic heterogeneity which was related to a variable number of sialic acid residues. The N terminus of Uλ is blocked (PCA). The deletions of both the λ- and the H chains were localized to their respective V regions and are of similar magnitudes (approximately 10,000 daltons). Possible genetic mechanisms to explain apparently comparable H- and L-chain deletions in a single IgG molecule are considered.