The nail changes observed in alopecia areata include diffuse fine pitting, onychorrhexis, Beau's lines, longitudinal ridging, onychodystrophy and trachyonychia. Nail changes may either precede, accompany or follow the hair loss. The presence of nail changes in alopecia areata is usually considered as an indicator of severity of the disease and reflects a more refractory disease as compared to patients without nail changes.
Ref: Modani S, Shapiro J. Alopecio areata update. J Am Acad Dermatol 2000; 42:549-566.