When this 45-year-old man was in third grade, he began to notice areas of hair loss in his scalp. The affected area was always round and the hair loss complete—but it would grow back entirely within weeks to months. There was never any rash or discomfort associated with these changes.
Since then, he has experienced numerous similar episodes of focal hair loss, sometimes in the beard, sometimes on the arms or legs, and most recently, in his eyebrows. Again, no symptoms accompany the process.
Although his personal health history is relatively uneventful, his family has not been as fortunate. There are numerous cases of lupus, rheumatoid arthritis, diabetes, and thyroid disease.
There are sharply defined, crescent-shaped, 2.5-cm divots at the superior borders of both eyebrows in which every hair is gone. No redness, swelling, or scaling are seen or felt, and there is no detectable adenopathy in the region.
Examination of hair-bearing regions reveals no other areas of hair loss.
What’s the diagnosis?