Short Anagen Syndrome.

A 10-year-old healthy, Caucasian girl presented in May 2021 with short and thin scalp hair since birth (Figures 1A-C). She had achieved all of her developmental milestones, and her parents denied any similar family history. She had only two hair cuts in the past, which were performed to trim long hair over the midscalp to have a uniform length. Hair at the front, back, and sides of the scalp were never trimmed. Examination revealed short, dark, and thin hair, varying in length from a few millimeters to 2 cm, over the frontal, parietal, and occipital areas. Longer hair were present over the midscalp, varying in length from 5 cm to 8 cm. The hairpull test was negative, and dermatoscopic examination of short hair demonstrated tapered ends, rather than cut ends. Microscopic examination revealed no hair shaft abnormality, and a trichogram of 50 parietal hair fibers demonstrated an anagen versus telogen ratio of 68:32. No associated skin, dental, or nail abnormalities were discovered.