254 P. SOUPART 
New provisional classification of aminoaciduria in pathological disorders 
Aminoaciduria of the common type, involving all urinary free amino acids. This type 
of pathological picture may be due either to congenital or acquired conditions. It 
is not, at first, generalized to all amino acids, but starts with hyperexcretion of the 
amino acids which are the less well reabsorbed in physiological conditions. When 
the disorder extends the hyperaminoaciduria progressively affects all amino acids. 
There is thus only a matter of degree which could distinguish the condition at its 
starting point and the situation when the condition has fully developed. Three sets 
of circumstances may lead to such amino acid excretion patterns: 
(1) Increased blood plasma amino acid concentrations, resulting in a true “over- 
flow” aminoaciduria. The urinary amino acid excretion pattern seems to be related 
to the type of cells specifically involved in the disorder, since tissues differ in their 
relative free amino acid composition. (2) The unusual process may not involve in- 
creased plasma amino acid concentration but, on the contrary, may result in lower 
plasma concentration, the intact reabsorption mechanism being overloaded by an 
increased glomerular filtration rate. Such an occurrence is found for instance in normal 
pregnancy. (3) Free amino acid levels in plasma are normal or even lowered, the 
glomerular filtration rate is normal, but there is still a generalized hyperamino- 
aciduria which is attributable to an impaired reabsorption function, as is the case 
in the so-called “De Toni-Debré-Fanconi syndrome”, among the congenital dis- 
orders, and possibly that of vitamin D deficiency, among acquired ones. 
These three processes do not depart very far from the three main categories of 
DEnT’s classification, although they do not show up in full development at first. 
Specific types of aminoaciduria involving a limited number of free amino acids. Here 
too, two different types of pathogenic mechanisms must be recognized: congenital 
and acquired conditions. Among the first category of situations one may rank 
genetic metabolic blocks, namely aromatic acid metabolic disturbances and essential 
cystinuria, as well as “maple-sugar-urine disease”. Among acquired disorders, all 
situations are characterized by a common feature, there is always a tissue break- 
down to be found resulting in taurine and BAIBA hyperexcretion. It is realized 
that the main distinction submitted here is only valid as a working hypothesis since 
in most cases, either sound information is not available or the available data have 
been provided by means of methods actually considered as unreliable. 
After these preliminary statements, one may reconsider a provisional but practical 
classification on the following basis: 
1) The anomaly is a congenital metabolic block, involving one or more amino 
acids and resulting in a hyperaminoaciduria of the generalized type. 
2) The anomaly results from a defect of the proximal convoluted tubule. The 
process may be either congenital or acquired and the resulting hyperaminoaciduria 
is still of the common generalized type. 
3) The primary pathogenic factor is congenital in nature but may also involve 
metabolic disturbance of substances other than amino acids. It results, nevertheless, 
in a secondary hyperaminoaciduria of the common generalized type. 
4) The anomaly results from an acquired condition, inducing either a generalized 
hyperaminoaciduria of the common type or an hyperexcretion of a limited number 
References p. 261/262 
