2256 



MISCELLANEOUS DISEASES 



THE HYPERKERATOSES. 



Definition. — A hyperkeratosis is any cutaneous condition in 

 which the cells of the horny layer have a greater coherence than 

 normal, as tested with pepsin and hydrochloric acid, and thus tend 

 to pile themselves up in the form of horny scales. 



Remarks. — ^^As defined above, a hyperkeratosis is more a symptom 

 than a disease, and most of the so-called primary hyperkeratoses are 

 probably induced by some chemical change produced by an altered 

 metabolic condition brought about by some infection. 



Thus syphilis and framboesia tropica are often believed to be the 

 disturbing element which lays the foundation of these changes, even 

 though no sign of their specific germs can be found in the lesions, 

 which may appear long after the disappearance of other features of 

 the disease, while the specific treatment for these complaints has 

 little or no influence on the hyperkeratosis. 



Further, syphilis can certainly act upon the foetus in utero and 

 lay the bases of changes of metabolism, which may result in the 

 so-called congenital hyperkeratosis, and the same remarks, to a 

 certain extent, appear to apply also to tuberculosis. 



Classification. — ^With the above provisos, the hyperkeratoses may 

 be classified into: — 



A. Hyperkeratoses obviously associated with a causal disease : — 



1. Non-jollicular : — 



Found in leprosy, arsenical poisoning, and hyperi- 

 drosis, 



2. Follic'ular : — ■ 



Found in various tubercular and syphilitic affections, 

 and some forms of lichen and acne. 



B. Hyperkeratoses oj unknown origin or remotely associated 



with syphilis, yaws, tuberculosis, etc.:- — 



[a) Develops during intra-uterine lije : — 



Hyperkeratosis universalis congeniic. 



(b) Develops during post-uterine life : — 



1. Generalized affections:- — 



Of these, ichthyosis and pityriasis rubra pilaris 

 are met with in the tropics. 



2. Localized affections: — 



(i.) Non-jollicular : — 



(1) Without acanthosis or markedly dilated 



papillary vessels' — K^f^^todermia. 



(2) Without acanthosis, but with markedly 



dilated papillary vessels — Angiokerato- 

 dermia. 



(3) With acanthosis, but without markedly 



dilated papillary vessels — Acantho- 

 keratodermia. 

 (ii.) Follicular — Keratosis, 



