Median Canaliform Nail Dystrophy

In dermatology, median canaliform nail dystrophy refers to an abnormal change in the nail plate characterised by a midline longitudinal furrow or split transverse ridges in a fir-tree pattern that are angled backwards.

Median canaliform nail dystrophy can affect anyone at any age, including children. Men and women are affected equally. Familial cases of median canaliform nail dystrophy have also been reported.

Microtrauma of the nail matrix is responsible for causing median canaliform nail dystrophy. It results in a temporary defect in keratinocyte adhesion, which affects the nail plate's tensile strength.

Cases are generally classified as either sporadic or idiopathic.

Habitual picking of the nail fold can cause a similar but distinct nail dystrophy. In rare cases, these conditions co-exist.

Generally, median canaliform nail dystrophy involves both thumbnails, but the condition can also be unilateral. Other fingernails and toes can be affected as well.

The longitudinal split extends from the proximal nailfold to the free edge of the nail. It is usually found within the midline but may occur off-centre.

The transverse ridges or splits are parallel and angled back towards the nailfold.

Median canaliform nail dystrophy is diagnosed based on clinical features. However, further investigations may be undertaken in order to exclude an underlying tumour.

Active treatment is not always required. General measures are recommended, such as applying a bandage to an affected nail to prevent further trauma. If an implicated medication such as isotretinoin is being taken, discontinuation is advised.

No specific treatment has been found to be effective for median canaliform nail dystrophy. Suggested treatments include topical steroids, topical tacrolimus, and phototherapy.

Median canaliform nail dystrophy usually arises spontaneously over months or years and can recur several times over a person's lifetime.