Hyperkeratosis

Tretinoin COOH Topical 0.025-0.1% Gels or creams Acne vulgaris, parakeratosis, hyperkeratosis Photoaging, actinic keratosis... 

May appear clinically as a cutaneous horn due to the significant hyperkeratosis. 

Lawrence et al. [66] in a split face study, compared the efficacy and safety of Jessner s solution and 35% TCA with 5% fluorouracil in the treatment of widespread facial actinic keratoses. Fifteen patients were treated. Both treatments reduced the number of visible actinic keratoses by 75%. Similarly, both caused equivalent reductions in keratinocyte atypia, hyperkeratosis, and parakeratosis. Compared to fluorouracil, only one application of the peel was necessary. 

Rabbit Ear Bioassay for Acnegenic Activity. Acnegenic activity of 2-7-DCDD, 1,2,3,4-TCDD, 2,3,7,8-TCDD, HCDD, and OCDD was tested by applying 0.1 ml of either a solvent solution or the supernatant of a solvent suspension of each compound to the inner surface of the rabbit s ears five days a week for four weeks. The ears were examined weekly for signs of chloracne, inflammation, and hyperkeratosis. The responses were divided into five categories (1) none, (2) very slight, (3) slight, (4) moderate, and (5) severe. 

In humans and rabbits contamination of the skin with TCDD produces chloracne-like lesions (3, 4). This disease is characterized by the appearance of hyperkeratosis, papules, comedones, and cysts. 

A number of skin diseases, mainly characterized by blistering, have been found to be due to mutations in genes encoding various keratins. Three of these disorders are epidermolysis bullosa simplex, epidermolytic hyperkeratosis, and epidermolytic pahnoplantar kerato-derma. The blistering probably reflects a diminished capacity of various layers of the skin to resist mechanical stresses due to abnormalities in microfilament strucmre. 

Keratinocyte proliferation is central to the clinical presentation of psoriasis. Keratinocytes are skin cells producing keratin which act as a skin barrier. Increased keratinocyte cell turnover (hyperkeratosis) results in the characteristic thick scaly skin lesions seen in patients with psoriasis.10,11 Hyperkeratosis results from immune derangements. 

Salicylic acid is one of the most commonly used keratolytics. It causes a disruption in corneocyte-to-corneocyte cohesion in the abnormal horny layer of psoriatic skin. This serves to remove scales, smooth the skin, and decrease hyperkeratosis. The keratolytic effect enhances penetration and... 

Dermal Effects. No studies were located regarding dermal effects in humans after exposure to disulfoton. Dermal lesions consisting of acanthosis, hyperkeratosis, ulceration of the skin, exudate formation, and epithelial inclusion cysts were found in male and female rats exposed chronically to the high dietary concentration of disulfoton (Hayes 1985). However, in intermediate- duration studies,... 

Nonneoplastic proliferative lesions of the forestomach were observed in high-dose Osborne-Mendel rats in the chronic gavage study of 1,2-dibromoethane conducted by the National Cancer Institute (NCI 1978). These consisted of acanthosis and hyperkeratosis of forestomach squamous epithelium. Similar lesions occurred in high-dose B6C3Fi mice. These dose levels are not plotted and recorded in Figure 2-2 and Table 2-2, respectively, since these doses also caused forestomach squamous cell tumors. 

Deficienqr of vitamin A results in night blindness (rod cells are responsible for vision in low light), metaplasia of the corneal epithelium, dry eyes, bronchitis, pneumonia, and follicular hyperkeratosis. 

Practolol (Figure 8.13) was the prototype cardioselective p-adrenoceptor blocking agent. Selectivity was achieved by substitution in the para position with an acetyl anilino function. The similarity of this drug with those outlined above is obvious. Practolol caused severe skin and eye lesions in some patients which led to its withdrawal from the market [6]. These lesions manifested as a rash, hyperkeratosis, scarring, even perforation of the cornea and development of a fibrovascular mass in the conjunctiva, and sclerosing peritonitis. Some evidence is available that the drug is oxidatively metabolized to a reactive product that binds irreversibly to tissue pro-... 

In a study of five workers exposed for 7-12 years to concentrations of 80-2 00 ppm at peaks, the principal findings were blackening and hyperkeratosis of the skin of the hands, conjunctivitis (but no corneal damage), bronchitis and pharyngitis, and erosion of the exposed teeth (incisors and canines). Digestive disorders with pyrosis and constipation have also been reported at unspecified prolonged exposures." ... 

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