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Wyprysk z hiperkeratozą - Objawy, Diagnoza i Leczenie
Pathophysiology
The skin is composed of three layers: the epidermis, the dermis (composed of the superficial papillary and deeper reticular dermis), and the hypodermis. The skin has structural differences among the different areas of the body in terms of epidermal and dermal thickness, distribution of appendages, and pigmentation. The epidermis is composed of multiple layers of maturing keratinocytes: the basal layer (stratum basale), the squamous layer (stratum spinosum), the granular layer (stratum granulosum), and the cornified layer (stratum corneum). This stratified epithelium is in a constant process of self-renewing and exfoliation that takes 20-40 days to complete. The cells in the outer layer are the most differentiated in the keratinocyte line, composed almost entirely of keratin lamels of high molecular weight, and those are the ones that undergo desquamation, completing the maturation cycle.
When the epidermis is exposed to repetitive injury, it usually elicits an increased proliferative rate of the keratinocytes and accelerates their maturation. Keratinocytes also tend to produce more keratin, thus increasing the stratum corneum's thickness.
Genetic mutations resulting in hyperkeratosis is seen in ichthyoses and keratoderma. There are several damages in keratin-encoding genes such as KRT1 and KRT10, which cause defects in keratin structure. Defective keratin causes irregular aggregates of intermediate filaments, which leads to cellular collapse and blistering. The barrier function is then compromised, and the skin reacts with compensatory hyperproliferation, which leads to hyperkeratosis.
Evaluation
Dermoscopy is noninvasive and allows visualization of the skin structures in the epidermis, dermo-epidermal junction, and superficial dermis.
A biopsy is essential in cases in which the clinical setting is overlapping with different entities having distinctive histopathologic findings. For an ideal full-thickness biopsy, it is important to include the hypodermis. This can be performed with a simple 3 mm punch that minimizes scarring in the affected area. Any smaller size is at risk of being non-diagnostic.
Patch tests can be useful for identifying the causative allergen if an allergic dermatitis is suspected. Clinical clues are the presence of persistent, pruritic, eczematous eruptions in which any other identifiable cause has been excluded. If the patient tests positive, they should be encouraged to avoid the specific allergen. A follow-up after a few weeks of allergen avoidance is strongly recommended.
Types of Hyperkeratosis
"Hyperkeratosis" is an umbrella term for skin conditions that develop from excess amounts of keratin. There are various types of hyperkeratosis, each marked by its cause.
Hereditary Types of Hyperkeratosis
Some types of hyperkeratosis develop due to a hereditary component. Examples include:
- Epidermolytic hyperkeratosis
- Multiple minute digitate hyperkeratosis (MMDH)
- Focal acral hyperkeratosis
- Lamellar ichthyosis
- X-linked ichthyosis (XLI)
- Keratosis pilaris, otherwise known as follicular hyperkeratosis
Acquired Hyperkeratosis
Other forms of hyperkeratosis are acquired later in life. It’s not always clear what the cause of each type is. Some acquired hyperkeratosis conditions include:
Acquired vs. Hereditary
Hereditary conditions are passed down through families. Often if a person is related by blood to someone with a genetic disorder, their risk of getting it is a lot higher. Acquired conditions, on the other hand, develop for many reasons unrelated to genetics.