Keloid

Definition: Keloids are hypertrophic, smooth, hard growths or scars that occur on the skin as a result of excessive scar formation. Keloids may rarely occur spontaneously. They may develop on any part of the body and extend beyond the original wound margins. The upper chest, shoulders, ears and neck are especially prone to keloid scar development.

Etiology: Keloids result from abnormal wound healing in response to skin trauma or inflammation. Their development is dependent on genetic or environmental factors. Keloids are most common in wounds that heal by secondary intention and can arise months to years following injury. The pathogenesis may involve dysregulation of the normal healing process, resulting in excessive production of collagen, elastin, proteoglycans and extracellular matrix proteins. In keloid scars, there is a defect in growth factors and cytokines, with increased TNF-alpha, interferon- beta and interleukin- 6.

Epidemiology: There is a higher incidence of keloids in darker-skinned individuals of African, Asian and Hispanic descent (Fitzpatrick skin types III-VI). Caucasian and Albino individuals appear to be less affected. A genetic association with HLA haplotypes and blood group A has also been identified. Spontaneously arising keloids have been associated with a variety of conditions like Noonan syndrome and Rubinstein-Taybi syndrome.

Signs: Keloid scars are benign, derma growths that may appear 1- 12 months following injury. They can develop anywhere but most commonly appear on the deltoid, pre- sternal chest, upper back and ear.  They present as firm, rubbery nodules which project above the underlying skin further than 4 millimeters. They may be pedunculated, or develop into a broad-base plaque. Colour ranges from flesh-coloured, erythematous or hyperpigmented and may change with the evolution of the lesion. 

Symptoms: Keloids are benign but frequently symptomatic. Patients may experience pruritus, pain, tenderness and burning.

Differentials: Hypertrophic scars, dermatofibroma, dermatofibrosarcoma protuberans, keloidal variants (morphea and scleroderma), xanthoma disseminatum, lobomycosis.

Diagnosis: Diagnosis of a keloid is primarily clinical based on the history and features. A biopsy is not required unless the diagnosis is unclear. 

Treatment: Primary prevention is key. Keloids are difficult to treat as incomplete therapy may result in worsening and growth of the scar. Several modalities alleviate symptoms of existing keloids such as intralesional corticosteroids, cryotherapy, surgical excision, radiotherapy and laser therapy. 

References:

1.     Keloids and hypertrophic scars | DermNet NZ. dermnetnz.org. https://dermnetnz.org/topics/keloid-and-hypertrophic-scar

2.     McGinty S, Siddiqui WJ. Keloid. In: StatPearls. Treasure Island (FL): StatPearls Publishing; July 17, 2023.