PROCEEDINGS 
OF THE 
NATIONAL ACADEMY OF SCIENCES 
Volume 4 AUGUST 15, 1918 Number 8 
HEREDITARY TENDENCY TO FORM NERVE TUMORS 
By C. B. Davenport 
Station for Experimental Evolution, Carnegie Institution of Washington 
Read before the Academy, April 23, 1918 
The term multiple neurofibromatosis is applied to a rather rare condition 
characterized by the appearance of numerous sessile or pedunculated swell- 
ings or tumors of varying consistency and size. These may be present from 
birth, tend to grow larger and may even become confluent over a con- 
siderable area. Examination shows that they are fibrous tumors and fre- 
quently contain one or more nerve fibers or, if more deep seated, may be 
enlargements of the perineurium of nerve trunks. They are due to cell pro- 
liferations of the connective tissue sheaths of nerves. 
The course of the disease is influenced by metabolic changes in the body. 
Thus pregnancy frequently stimulates growth of the small tumors which have 
been present from birth. In other cases even the changes of puberty are 
associated with the first marked development of the tumors. After various 
zymotic diseases, arsenical and lead poisoning, rapid growth of the tumors 
has been observed. The numbers of tumors may be very great, as many 
as 2000 or 4000. The tumors may be stimulated to grow by external me- 
chanical agencies also, such as the irritation of a sword belt. 
Associated with the tendency to form tumors is the production of pig- 
mented spots or patches in the skin — of a cafe au lait color. Such patches 
when of small size may grow into colored moles or small tumors. On au- 
topsy tumors are frequently found on the deeper lying nerves. 
Multiple neurofibromatosis is a rare condition ; it is found in only about 1 in 
2000 cases that present themselves to medical clinics or private practitioners 
for skin diseases. Despite this there are many cases in the literature where 
2 to 6 members of a family show some of the symptoms. The fact that 
only blood relatives are affected indicates that the disease is not a communi- 
cable one and it is equally certain that it is not induced by infection through 
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