Keloids are a type of raised scar that grows beyond the boundaries of the original wound site. This excessive growth is caused by an overproduction of collagen during healing, often leading to a firm, rubbery lesion that can cause pain or itching. Intralesional injection therapy is a first-line medical approach for managing these scars. This method involves delivering medication directly into the scar tissue to help flatten and soften the lesion.
The Mechanism of Intralesional Steroid Injections
The substance most commonly injected into keloids is a corticosteroid, specifically triamcinolone acetonide (TAC). The term “intralesional” means the drug is placed directly within the dense, collagen-rich tissue of the keloid, bypassing the outer skin layer. This delivery method allows a high concentration of the drug to reach the target site, maximizing its effect while minimizing potential systemic side effects.
TAC works by disrupting the abnormal healing cycle that creates the keloid. The corticosteroid decreases inflammation, which drives excessive tissue growth, and suppresses the proliferation of fibroblasts. Fibroblasts are the cells responsible for synthesizing collagen.
By inhibiting fibroblast activity, the injection reduces the synthesis of new collagen and glycosaminoglycans, the components that give the keloid its bulk. TAC also enhances the breakdown of existing collagen within the keloid. This combination of reduced production and increased degradation ultimately leads to the flattening and softening of the scar over time.
The Treatment Protocol and Procedure
The procedure for intralesional injection is tailored to the individual keloid, but it follows a standard protocol. The medication is injected using a fine-gauge needle (typically 26 to 30-gauge), which can be challenging due to the toughness and density of the keloid tissue. The goal is to inject the substance into the middle layer of the dermis within the scar until the tissue visibly blanches, or turns pale, indicating proper drug saturation.
The concentration of triamcinolone acetonide ranges from 10 mg/mL for moderate scars to 40 mg/mL for thicker, more mature lesions. The total dosage per session is carefully monitored, typically ranging from 20 mg to 80 mg depending on the size of the lesion. To aid in drug dispersion and reduce the discomfort associated with injecting into dense tissue, the corticosteroid is sometimes diluted with a local anesthetic.
Patients typically receive injections in a series, with sessions scheduled every four to eight weeks. A full course of treatment often requires between three and seven sessions before the maximum benefit is achieved. The exact number of treatments depends on how the keloid responds, with clinical improvement often becoming noticeable after the second or third injection.
Anticipated Results and Recurrence Rates
Intralesional steroid injections show initial keloid flattening or regression rates ranging from 50% to 100% of treated lesions. Beyond cosmetic changes, the treatment is highly successful in relieving associated symptoms, such as the pain and persistent itching (pruritus) that often accompany keloids. Patients experience significant softening and a reduction in the height and redness of the lesion.
Despite the high initial success, a challenge with this therapy is the rate of recurrence. When used as a standalone treatment, keloids can regrow, with recurrence rates reported between 9% and 50% over a period of one to five years. Recurrence is influenced by factors such as the keloid’s original size, its location on the body, and the total duration of the treatment course.
Because of the risk of recurrence, injections are often incorporated into a combination therapy approach, particularly following surgical excision of the keloid. Adjuvant therapy, such as post-operative injections, has been shown to significantly lower the recurrence rate. For lesions that do not respond well to corticosteroids alone, combining the injection with other agents like 5-fluorouracil can yield superior results.
Managing Potential Side Effects
While intralesional injections are localized to the scar, the introduction of a corticosteroid can lead to specific side effects in the surrounding skin. The most common adverse reactions include changes to the skin and subcutaneous tissue near the injection site. Skin atrophy, or thinning of the skin, can occur, which may present as a slight indentation or dimple.
Other frequent side effects are pigmentary changes, which include both hypopigmentation (lightening of the skin) and hyperpigmentation (darkening of the skin). The injection can also cause telangiectasias, which are small, visible, spider-like blood vessels that appear on the skin surface. These localized side effects are more likely to occur with higher drug concentrations or if the injection is inadvertently placed too superficially outside the dense keloid tissue.
Systemic side effects are uncommon because the drug is delivered directly into the lesion in small, controlled doses. However, pain and bruising at the injection site are common immediate effects. The risk of side effects is a factor that medical professionals weigh carefully when determining the appropriate concentration and frequency for each patient.