What skin condition is caused by insufficient vitamin A in the diet?

Vitamin A plays a crucial role in maintaining healthy skin as it is essential for cell differentiation and turnover. Insufficient levels of vitamin A can lead to hyperkeratinisation, which is the excessive production of keratin, the protein that makes up the outer layer of skin. This condition results in thick, dry, and scaly patches on the skin, as the skin cells do not shed properly and accumulate.

The other options represent different skin conditions that arise from various causes. Hyperpigmentation is an uneven skin tone resulting from excess melanin production, which is not directly linked to vitamin A deficiency. Dermatitis refers to inflammation of the skin that can occur due to many factors like allergens or irritants, rather than a vitamin deficiency. Alopecia is the loss of hair, which can stem from numerous reasons such as hormonal changes or autoimmune disorders, but it is not a direct consequence of inadequate vitamin A intake. Thus, hyperkeratinisation is clearly associated with low levels of vitamin A in the diet.