Differential Diagnosis for Pink Macule with Bruising Underneath
Single Most Likely Diagnosis
- Psoriatic plaque with excoriation and bruising: Given the patient's history of psoriasis, a pink macule with bruising underneath could represent a psoriatic plaque that has been excoriated, leading to bruising. Psoriasis can cause erythematous plaques, and if these are scratched or picked, they can bleed and bruise.
Other Likely Diagnoses
- Eczema (atopic dermatitis) with excoriation and bruising: Similar to psoriasis, eczema can cause itchy, erythematous lesions that, when scratched, can lead to excoriations and bruising.
- Seborrheic dermatitis with excoriation and bruising: This condition causes a red, itchy rash, typically on the scalp, but it can also occur on oily areas of the body. Scratching can lead to bruising.
- Contact dermatitis with excoriation and bruising: An allergic or irritant reaction to a substance can cause a pink macule that, if scratched, can bruise.
Do Not Miss Diagnoses
- Malignancy (e.g., basal cell carcinoma, squamous cell carcinoma): Although less likely, a new, unexplained lesion with bruising could potentially be a sign of skin cancer. It's crucial to consider this possibility, especially in older adults or those with a history of skin cancer.
- Vasculitis: Certain types of vasculitis, such as leukocytoclastic vasculitis, can present with purpura (bruising) and may initially appear as a pink macule.
- Infection (e.g., cellulitis, erysipelas): Bacterial infections of the skin can cause redness, swelling, and bruising. It's essential to consider infection, especially if there are signs of systemic illness or if the lesion is rapidly progressing.
Rare Diagnoses
- Mastocytosis: This condition is characterized by an accumulation of mast cells in the skin and can cause lesions that are prone to bruising due to mast cell degranulation.
- Amyloidosis: Certain types of amyloidosis can cause skin lesions and purpura due to the deposition of amyloid proteins in the skin.
- Scurvy: Vitamin C deficiency can lead to poor collagen synthesis, resulting in fragile blood vessels that are prone to bruising. Skin lesions in scurvy can appear as pink macules with surrounding bruising.