desquamation

Desquamation is the shedding or peeling of the outermost layer of the skin, the corneocytes of the stratum corneum. It is a normal part of skin renewal but can be accelerated or abnormal in disease. The process involves the breakdown of corneodesmosomes, the junctions that hold corneocytes together, by proteolytic enzymes, allowing cells to detach and shed. In healthy adults, epidermal turnover takes about 28 days, and desquamation is a regulated, gradual event.

Mechanistically, keratinocytes proliferate in the basal layer and migrate outward as they differentiate. The corneocytes are linked by corneodesmosomes; proteases such as kallikreins cleave these connections, and their activity is balanced by inhibitors and environmental factors like humidity, pH, and skin hydration. Disruptions in this balance can lead to increased or abnormal shedding.

Clinical contexts include both physiologic and pathologic desquamation. Physiologic shedding occurs during wound healing, after sunburn, or in newborns who shed vernix-covered skin. Pathologic desquamation is associated with conditions that produce excessive scaling or epidermal turnover, such as exfoliative toxins in staphylococcal scalded skin syndrome, toxic epidermal necrolysis, severe contact dermatitis, psoriasis, ichthyoses, fungal infections, and drug reactions.

Diagnosis relies on history and physical examination; investigations are guided by suspected underlying causes and systemic involvement. Management targets the underlying condition and supportive skin care, including gentle cleansing and regular moisturization. Severe or widespread desquamation, particularly with systemic symptoms or mucous membrane involvement, warrants urgent medical evaluation and appropriate treatment.