A keloid refers to a chronic, persistent scar-like plaque or nodule that extends beyond the site of an original skin injury due to excessive deposition of collagen in the dermis by fibroblasts. A hypertrophic scar is confined to the site of the original wound and can self-resolve. Keloids can be very itchy and painful. Patients also seek treatment for the psychosocial impact they can have related to the appearance. Simple excision is rarely effective, as they almost always recur.
Keloids are more common, and tend to grow larger, in people with dark skin and Asians. They typically occur between ages 20-30 years in both women and men. The elderly and young children are rarely affected. Sometimes, keloids occur in families.
It’s unknown why some individuals tend to develop keloids and others do not. The pro-fibrotic cytokine, transforming growth factor beta (TGF-beta) plays a key role. Keloids tend to occur after trauma, but not always.
Common triggers of keloids:
Keloids are well-demarcated, firm, scar-like, irregularly-shaped, plaques or nodules, usually arising in a site of previous skin injury. The overlying epidermis is shiny and thin. Lesions often progress from pink to red to purple with surrounding erythema, and telangiectasias and can be itchy, tender or painful.
A patient will often have more than one lesion. They range in size from a few millimetres to more than 10 centimetres. Keloids can be linear, often bulbous at the ends with central regression, or spherical. They are distinguished from a hypertrophic scar by extending beyond the margins of the original injury, sometimes with claw-like extensions.
Keloids can occur anywhere, but favour sites with increased skin tension such as:
The main differential diagnosis to consider is a hypertrophic scar. For atypical lesions, without preceeding injury, consider keloidal forms of morphea, and scleroderma, as well as dermatofibroma, or rarely, dermatofibrosarcoma protuberans. Complications include hyperpigmentation, ulceration and draining sinus tracts.
Keloids are mainly a clinical diagnosis. If the history or clinical findings are not classic for a keloid, or if there are any doubts, consider taking a biopsy of the lesion for histopathology to rule out a malignancy. Under the microscope, a keloid shows large thick, hyalinized collagen bundles in the dermis, pushing other structures aside.
Treating keloids is challenging, as they have a poor response to interventions, and — unlike hypertrophic scars — they rarely self-resolve. Many options are available and there is no single best treatment. It is difficult to predict which one a patient may respond to and combinations are often more helpful than any one therapy. Key components include patient education and prevention.
Strategies for prevention:
Treatment options for keloids
Charles Lynde, MD, FRCP(C) is an assistant professor of dermatology at the University of Toronto.
John Kraft, MD, is in his third year of the Dermatology Residency Program at the University of Toronto.