Differential Diagnosis for Acne on the Lateral Neck

The patient's presentation of acne primarily on the left side of the lateral neck, inferior to the ear lobe, with slight involvement on the right side, suggests several potential diagnoses. These can be categorized as follows:

• Single Most Likely Diagnosis
  • Acne vulgaris: This is the most common form of acne and can occur on various parts of the body, including the neck. The location and description provided are consistent with acne vulgaris, which is often seen in areas with a high concentration of sebaceous glands.
• Other Likely Diagnoses
  • Folliculitis: An inflammatory condition affecting the hair follicles, which can be caused by bacterial, viral, or fungal infections. The symptoms can resemble acne and may occur on the neck.
  • Keratosis pilaris: A condition characterized by small, rough, sandpapery bumps on the skin, often on the arms, legs, buttocks, and occasionally the neck. While it doesn't typically present as acne, it could be considered in a differential diagnosis for skin lesions on the neck.
  • Seborrheic dermatitis: A skin condition causing scaly patches, red skin, and stubborn dandruff, often affecting oily areas of the body like the face and, less commonly, the neck.
• Do Not Miss Diagnoses
  • Lymphoma or other malignancies: Although rare, certain types of lymphoma or skin cancers can initially present with skin lesions that might be mistaken for acne. It's crucial to consider these possibilities, especially if the lesions are persistent, growing, or accompanied by other systemic symptoms.
  • Tuberculosis (TB) or atypical mycobacterial infections: These infections can cause skin lesions that might resemble acne, particularly in immunocompromised individuals. A high index of suspicion is necessary, especially if there are systemic symptoms or risk factors for TB.
• Rare Diagnoses
  • Sarcoidosis: A condition that can affect multiple parts of the body, including the skin, and might present with lesions that could be confused with acne.
  • Granuloma faciale: A rare skin condition characterized by single or multiple, soft, brownish to purple plaques or nodules, typically on the face but could potentially occur on the neck.
  • Halogenoderma or bromoderma: Rare conditions caused by exposure to halogens (like bromine or iodine), leading to skin lesions that might resemble acne.

Each of these diagnoses has a different set of implications for treatment and management, emphasizing the importance of a thorough evaluation to determine the underlying cause of the patient's symptoms.