Hypotrichosis is a medical condition characterized by the absence or reduction of hair growth. It can be congenital, meaning present at birth, or can develop later in life. The condition can affect any part of the body, though it's often noticed on the scalp. Hypotrichosis differs from Alopecia, which refers to hair loss where hair previously grew. The cause of Hypotrichosis can vary and may be due to genetic factors underlying medical conditions or unknown reasons.