906 WARD J. MAcKEAL 



Diagnosis 



The diagnosis has to be made by examination of the patient and may 

 be supported by subsequent demonstration of- the typical anatomical 

 changes in the tissues. Of the accessory facts, the most important is a 

 history of. having lived in a pellagrous district. The dietary history is of 

 considerable importance, also, but the inexperienced usually attach too 

 much, rather than too little, importance to this feature. Some authors 

 regard emaciation and physical weakness as evidence of pellagra, but 

 these signs are, of course, common to very many pathological conditions. 



Only the typical cutaneous eruption on the backs of the hands warrants 

 a definite and certain diagnosis of pellagra. The localization on the backs 

 of the hands and forearms, the approximate bilateral symmetry, its 

 sudden appearance as an erythema, gradual evolution to hyperkeratosis, 

 with or without hyperpigmentation, the subsequent desquamation and 

 restitution, with or without persistent atrophy, are important in the 

 recognition of the pellagrous eruption. A dermatitis due to molds may 

 simulate the pellagrous eruption, but such a dermatitis usually occurs else- 

 where than on the backs of the hands. Roussel, however, mentions cases 

 in which the differential diagnosis was finally decided only by the micro- 

 scopic demonstration of mycelial threads in lesions on the backs of the 

 hands. The developmental course of a mild dermatitis is usually differ- 

 ent,, also, so that continued observation may alone suffice for its differ- 

 entiation. 



A tentative diagnosis of pellagra is often justified without observa- 

 tion of the eruption. Certainly the disease is usually still present after 

 the eruption has disappeared, and there is abundant evidence that the 

 patient suffers from pellagra when the eruption is absent. However, 

 such a tentative diagnosis should be abandoned if the patient does not 

 subsequently present the eruption or confess to its earlier presence. 



Prophylaxis 



Preventive measures may be grouped in two classes ; first, those which 

 enhance the individual resistance to the disease, and, second, those which 

 diminish the opportunity for the specific causative factor to attack the 

 individual. In its endemic centers pellagra attacks only a small propor- 

 tion of the population at any one time, and the physically vigorous escape 

 it to a very large extent. The maintenance of robust physical vigor u, 

 therefore, an excellent insurance against pellagra. In every natural 

 cpmmunity, however, there will be some tender young children, some chil- 

 dren occasionally sick with measles or gastro-intestinal derangement, some 



