Hypercatabolism of IgG, IgA, IgM, and albumin in the Wiskott-Aldrich syndrome. A unique disorder of serum protein metabolism.

Abstract

The Wiskott-Aldrich syndrome is an immune deficiency disorder with an impairment of both humoral and cellular immune responses. Metabolic turnover studies of IgG, IgA, IgM, and albumin were conducted in seven patients with the Wiskott-Aldrich syndrome using purified radioiodinated proteins. The survival of each of the proteins studied was significantly shortened with a half-time of 7.5 days for IgG (normal 22.9 +/-4 SD), 3.0 days for IgA (normal 5.8 +/-1), 5.0 days for IgM (normal 10.1 +/-2.1), and 8.6 days for albumin (normal 17, range 13-20); the fractional catabolic rates were correspondingly elevated and the distribution of protein among the body compartments was normal. For three of the four proteins. IgG, IgA, and albumin, the steady-state synthetic rates were generally elevated leading to normal or even elevated serum proteins levels. Thus, in the case of IgA, the synthetic rate averaged five times normal while the fractional degradative rate was twice normal. The resulting serum concentration was, therefore, significantly elevated, IgM represented an exception to this pattern in that the increased rate of degradation was not counterbalanced by an increased synthetic rate and, therefore, the serum levels were low. Albumin clearance studies using albumin-(51)Cr showed gastrointestinal protein loss in these patients to be slightly greater than normal, but this could account for only a small fraction of the hypercatabolism observed. There was no proteinuria or abnormalities of thyroid, adrenal, renal, or liver function. Thus, none of the previously recognized causes of increased serum protein catabolism were present. Patients with the Wiskott-Aldrich syndrome, therefore, have a unique disorder of serum protein metabolism characterized by endogenous hypercatabolism of at least four major serum proteins. This phenomenon may be related to reticuloendothelial hyperfunction since the Wiskott-Aldrich syndrome is associated with reticuloendothelial hyperplasia and accelerated clearance of colloidal materials from the plasma.