Fourteen patients with idiopathic thrombocytopenic purpura (ITP) have been followed for one year after plasma exchange therapy. Exchange was performed prior to splenectomy in eight of nine patients with acute ITP and following splenectomy in five patients with chronic ITP. None with chronic ITP showed a response in platelet count as a result of exchange therapy. Four of the nine with acute ITP had poor responses and required splenectomy because of persistent severe thrombocytopenia. Three of these have responded completely and are in remission. One patient with acute ITP had an equivocal response, with a most recent platelet count of 93,000/microliter. The remaining four patients with acute ITP had prompt and complete responses and now have platelet counts above 100,000/microliter without steroid treatment. Although the good responses were temporally associated with the use of plasma but not albumin, the data are not sufficient to conclude that a plasma factor must be infused to obtain a satisfactory result. The overall response after one year was about that expected for acute ITP patients treated with prednisone and early splenectomy. Exchange plasmapheresis may be of value in decreasing the number of patients who require splenectomy, but a randomized, prospective study is needed to adequately assess this possibility.

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When blood plasma proteins are depleted by bleeding with return of red cells suspended in saline (plasmapheresis) it is possible to bring dogs to a steady state of hypoproteinemia and a constant level of plasma protein production if the diet nitrogen intake is controlled and limited. Such dogs are outwardly normal but have a lowered resistance to infection and intoxication and probably to vitamin deficiency. When the diet nitrogen is provided by certain mixtures of the ten growth essential amino acids plus glycine, given intravenously at a rapid rate, plasma protein production is good. The same mixture absorbed subcutaneously at a slower rate may be slightly better utilized. Fed orally the same mixture is better utilized and associated with a lower urinary nitrogen excretion. An ample amino acid mixture for the daily intake of a 10 kilo dog may contain in grams dl-threonine 1.4, dl-valine 3, dl-leucine 3, dl-isoleucine 2, l(+)-lysine·HCl·H2O 2.2, dl-tryptophane 0.3, dl-phenylalanine 2, dl-methionine 1.2, l(+)-histidine·HCl·H2O 1, l(+)-arginine·HCl 1, and glycine 2. Half this quantity is inadequate and not improved by addition of a mixture of alanine, serine, norleucine, proline, hydroxyproline, and tyrosine totalling 1.4 gm. Aspartic acid appears to induce vomiting when added to a mixture of amino acids. The same response has been reported for glutamic acid (8). Omission from the intake of leucine or of leucine and isoleucine results in negative nitrogen balance and rapid weight loss but plasma protein production may be temporarily maintained. It is possible that leucine may be captured from red blood cell destruction. Tryptophane deficiency causes an abrupt decline in plasma protein production. No decline occurred during 2 weeks of histidine deficiency but the urinary nitrogen increased to negative balance. Plasma protein production may be impaired during conditions of dietary deficiency not related to the protein or amino acid intake. Skin lesions and liver function impairment are described. Unidentified factors present in liver and yeast appear to be involved.