Alopecia Areata: This is an autoimmune condition that leads to patchy hair loss, often on the scalp. It's a common cause of hair loss in young adults and can be triggered by stress, genetics, or other autoimmune diseases.

Androgenetic Alopecia (Female Pattern Hair Loss): This condition is influenced by genetics and hormonal factors, leading to thinning of hair over the scalp. It's common in women, especially after puberty.
Tinea Capitis (Ringworm of the Scalp): A fungal infection that can cause patches of hair loss, often accompanied by redness, itching, and scaling.
Telogen Effluvium: A condition that causes excessive hair shedding after a major body stress, such as severe illness, psychological stress, or major surgery.

Thyroid Disease (Hypothyroidism or Hyperthyroidism): Both underactive and overactive thyroid glands can lead to hair loss among other symptoms. Early detection is crucial for treatment and prevention of long-term complications.
Syphilis (Secondary Syphilis): This sexually transmitted infection can cause patchy hair loss, among other systemic symptoms. It's critical to diagnose and treat to prevent further complications and transmission.
Lupus: Systemic lupus erythematosus is an autoimmune disease that can cause hair loss, along with a variety of other symptoms including skin rashes, joint pain, and kidney problems.

Alopecia Monolocularis: A rare form of alopecia areata that affects one area of the scalp.
Trichotillomania: A psychological disorder characterized by an irresistible urge to pull out one's own hair, leading to noticeable hair loss.
Discoid Lupus Erythematosus: A chronic skin condition of sores with inflammation and scarring favoring the face, ears, and scalp but can occur on other body areas, leading to hair loss in the affected areas.