An Unknown Reducing Urinary Substance in Myasthenia Gravis.

Abstract

In the course of the determination of urinary inorganic phosphate by the method of Fiske and Subbarow 1 in a case of myasthenia gravis it was observed that the phosphomolybdic acid became reduced and an intense blue color developed before the reducing agent, aminonaphtholsulfonic acid, was added. The same immediate reduction of the phosphomolybdic acid did not take place after the acid digestion in the course of the total phosphorus determination. It was also observed that occasionally in this particular urine the inorganic phosphate figures slightly exceeded the values for total phosphorus. Attempts to elucidate this phenomenon have led to our present conception that we deal with a hitherto unknown reducing urinary substance.

We have obtained the same color reaction from the urines of two other cases of myasthenia gravis, but have failed to demonstrate the same in one case of muscular dystrophy and in one case of muscular atrophy, diseases in which as in myasthenia gravis a creatinuria is or may be present. Of our second and third cases of myasthenia gravis, which at the present show a milder clinical picture than our first case and from which only random samples of urine were obtained, none developed as deep a color as our first case. In one we designate the color as weak but definite, in the other as of moderate intensity. In normal urines we have never observed this reaction, which also must be in accordance with the experiences of Fiske and Subbarow. The only other condition in which we have observed a similar behavior is alkaptonuria.