VIII. VITAIMIX A DEFICIENCY IN HUMAN BEINGS l67 



avitaminosis A may occur separately as well as concurrently either in chil- 

 dren or adults. Their acceptance as typical, when isolated, phenomena 

 should be based upon their disappearance within 1 to 2 months under mod- 

 erate dosage of vitamin A concentrate and, if possible, on supporting evi- 

 dence of low plasma vitamin A levels or low dietary intake over prolonged 

 periods. Where subjects exhibit angular stomatitis as well, vitamin B- 

 complex therapy is often prerequisite to an adequate response to vitamin A 

 therapy.-'-' ^° 



Conclusions based upon those studies where the greatest care has been 

 exercised in dermatologic diagnosis, biopsy examination, and correlation 

 with other evidence of avitaminosis A indicate that infants and children 

 up to 4 to 5 years of age rarely show more than generalized xerosis of the 

 epidermis, and that during later childhood and adolescence there may be 

 superimposed upon this a mild type of follicular hyperkeratosis indistin- 

 quishable from, but less pronounced than, that characterizing avitaminosis 

 A in adults. 



3. HiSTOPATHOLOGY 



The cutaneous lesions of avitaminosis A represent a primary hyper- 

 keratinization and hyperplasia of the epidermis, including the lining of the 

 hair follicles and sebaceous glands. In a strict sense this is not a true meta- 

 plasia, as is seen in other epithelial surfaces affected by lack of vitamin A, 

 but rather an accentuation of a process of progressive keratinization nor- 

 mally inherent in this epithelial layer. Decreased function of sweat glands 

 and the follicular eruption which is so prominent a gross feature are the 

 later results of this primary process. 



In infants and young children under 5 years of age, before the piloseba- 

 ceous follicle has fully matured, there is usually only a simple xerosis, or 

 xeroderma. However, there may be moderate hyperkeratinization of the 

 follicle lining. The superficial epidermis is sometimes reduced in thickness'*'' 

 rather than hyperplastic. The stratum corneum is usually several times 

 its normal thickness and may cause blockage of sweat ducts. 



A more exaggerated picture is seen in adults with advanced keratoma- 

 lacia, as described first by Pillat^^ and studied microscopically by 

 Radhakrishna Rao.^^ The stratum corneum forms a broad network, or 

 even horny plates, and gives rise to a rather abundant des(iuamation of fine 

 scales. The stratum lucidum and stratum granulosum show no appreciable 

 change. Melanin increases in the basal layers, and the epidermis may be 

 thinned rather than hypertrophic. This atrophic thinning, often associated 

 with flattening of the papillary layer of the dermis, may reflect general 

 undernutrition. Sebaceous glands are greatly reduced in number; sweat 

 ducts are occluded by keratinous material, but the coiled glands are usually 



