Chromonychia

Chromonychia is the presence of abnormal nail color. The natural nail plate is translucent and derives its apparent color from the underlying structures. Certain internal diseases and medications can cause color abnormalities in the nail plate. External factors can stain and discolor the nail plate. When the pigmentation is caused by external factors, the change in pigmentation parallels the contour of the proximal nail fold and, when caused by internal factors, the change usually follows the lunula contour.

Brachyonychia

In brachyonychia, or short nails, the longitudinal dimension of the nail is shorter than normal, giving the fingernail an unusually broad appearance. This can occur as an isolated finding and there may be shortening of the terminal phalanx. The thumbs are commonly affected (racket nails) and this may be familial (Figures 7 and 8).

Beau’s lines

Beau’s lines are horizontal grooves in the nail plate that represent an arrest or slow-down in the growth of the nail matrix. A severe medical event such as surgery, allergic reaction to medication or serious trauma to the system can trigger Beau’s lines. The depth and width of the line speak to the abruptness and duration of the event. Beau’s lines move distally as the nail grows over time (Figure 6).

Anonychia

Anonychia is the absence of nail. It can occur as the end result of scarring (onychatrophy) (Figure 4) and in congenital disorders, often when there is malformation of the corresponding digit (Figure 5).

Nail Biopsy

When history and clinical features alone do not yield a diagnosis, a biopsy of the nail should be considered. The location of the nail biopsy is dependent upon which part of the nail unit is responsible for the pathological features of the nail. When the nail plate is abnormal, the pathological process is often located in the nail matrix or is a space occupying lesion in the nail fold. Nail bed and nail fold changes require biopsy of the appropriate area. If the clinician is not experienced or comfortable with the procedure of nail biopsy, a referral to a dermatologist should be considered.