Skin diseases and allergic reactions 

A congenital disorder characterized by the complete or partial absence of pigment (melanin) in the skin, hair and eyes.

Urticaria and angioedema are common hypersensitivity disorders characterized by recurrent episodes of transient wheals (hives) with or without deeper swelling of the skin and mucous membranes (angioedema). Urticaria results from the release of histamine and other inflammatory mediators from mast cells, leading to localized edema of the superficial skin. Angioedema involves deeper layers of the skin and subcutaneous tissues and commonly affects the lips, tongue, eyelids, and throat.

Post-herpetic neuralgia (PHN) is a chronic neuropathic pain condition that occurs as a complication of herpes zoster (shingles).

Dermoid cyst is a congenital benign cystic lesion that develops due to sequestration of ectodermal tissue during embryonic development. It contains skin structures such as hair follicles, sebaceous glands, and sweat glands and may also contain hair and sebaceous material.

Scleroderma is a chronic autoimmune connective tissue disease characterized by excessive collagen deposition leading to fibrosis of the skin and, in systemic disease, internal organs. The exact cause is unknown, but genetic susceptibility, immune dysregulation, and vascular injury contribute to disease development.