Acne vulgaris: This is the most common skin condition characterized by closed comedones (whiteheads) along the T-zone region of the face, which is greasy in nature due to the high concentration of sebaceous glands. The T-zone, including the forehead, nose, and chin, is particularly prone to acne due to its high sebaceous gland density.

Seborrheic dermatitis: While primarily known for causing a scaly, itchy rash, seborrheic dermatitis can also present with oily, greasy skin and may sometimes be confused with acne, especially in the T-zone area.
Keratosis pilaris: Although more commonly found on the arms and legs, keratosis pilaris can occasionally appear on the face, presenting as small, rough bumps that might be mistaken for closed comedones, especially if the skin is oily.

Rosacea: While rosacea is more commonly associated with redness, flushing, and visible blood vessels, some subtypes can present with oily skin and bumps that might resemble closed comedones. Missing this diagnosis could lead to inappropriate treatment and worsening of symptoms.
Folliculitis: An inflammatory condition affecting the hair follicles, folliculitis can present with bumps and oily skin, particularly if caused by bacterial or fungal infections. It's crucial to differentiate this from acne to provide appropriate antimicrobial treatment.

Trichoepithelioma: A rare skin condition characterized by the growth of benign tumors from hair follicles, trichoepithelioma can sometimes present as multiple small bumps on the face, potentially resembling closed comedones in the T-zone area.
Basal cell carcinoma: Although extremely rare to be mistaken for closed comedones, basal cell carcinoma can occasionally present as a solitary, pearly nodule. Given its potential for malignancy, it's essential to consider this in the differential diagnosis, especially in older adults or those with significant sun exposure history.