penebalan lapisan terluar kulit yang paling sering disebabkan karena kekurangan vitamin A.

Merriam-Webster Online Dictionary
hyperkeratosis (noun)
of the corneous layer of the skin - hypertrophy
Hyperkeratosis (Wikipedia)
Lichen simplex chronicus - low mag.jpg
Micrograph showing hyperkeratosis. H&E stain.
Classification and external resources
Specialty dermatology
ICD-10 L85.9
ICD-9-CM 701.1
DiseasesDB 20624

Hyperkeratosis is thickening of the stratum corneum (the outermost layer of the epidermis), often associated with the presence of an abnormal quantity of keratin, and also usually accompanied by an increase in the granular layer. As the corneum layer normally varies greatly in thickness in different sites, some experience is needed to assess minor degrees of hyperkeratosis.

It can be caused by vitamin A deficiency or chronic exposure to arsenic.

Hyperkeratosis can also be caused by B-Raf inhibitor drugs such as Vemurafenib and Dabrafenib.

It can be treated with urea-containing creams, which dissolve the intercellular matrix of the cells of the stratum corneum, promoting desquamation of scaly skin, eventually resulting in softening of hyperkeratotic areas.