Pellagra 



WAED J. MAcNEAL 



NEW YORK 



Definition 



Pellagra is a specific disease of man characterized by clinical signs and 

 symptoms, by geographical location and by seasonal relationships. The 

 clinical features include inflammation of the digestive tract, various grades 

 of toxic nervous disorders, and a peculiar cutaneous eruption which is 

 the most characteristic feature of pellagra. This is a symmetrical ery- 

 thema which involves especially the backs of the hands and passes regularly 

 through a stage of erythema, a stage of hyperkeratosis, a desquamative 

 stage to restitution with more or less atrophy of the skin. The location, 

 nature and evolution of this eruption has the same importance in the 

 diagnosis of pellagra as has the eruption of measles or of smallpox in the 

 diagnosis of these diseases. 



Etiology 



Specific Causation. Roussel in 1866 concluded that pellagra is caused 

 by two groups of factors. One of these, the extrinsic factor, is altered 

 maize, which is the specific cause of pellagra, giving to the disease its 

 character as a disease entity and without which there can be no pellagra. 

 However, there is required in addition certain conditions of vitality within 

 the body of the victim, just as seeds require suitable soil for their de- 

 velopment. All causes of enfeeblement create this necessary vital con- 

 dition of susceptibility. Such, says Roussel, is the dual basis indispensable 

 as a solid foundation for the etiologic theory of pellagra. This view of 

 Roussel contains much that is admirable and still deserving of re- 

 "spectful consideration. For nearly forty years it remained almost un- 

 challenged. Sambon in 1905 launched a most successful attack against 

 this maize theory, and numerous other investigators, following him, have 

 shown that pellagra occurs in those who do not eat maize, the possibility 

 of .which was absolutely denied by Roussel. Unfortunately, Sambon 

 coupled with his refutation of the maize theory the conception that pellagra 

 is an infectious disease transmitted by a biting fly of the genus Simuliam, 

 a theory which has been unable to withstand later investigation. 



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