Leukonychia totalis is a nail condition characterized by complete whitening of the entire nail plate. It is usually inherited in an autosomal dominant manner. Less commonly, it may be inherited in an autosomal recessive manner, or acquired (not inherited) during a person's lifetime. The inherited forms can be caused by mutations in the PLCD1 gene and generally involve the entire plate of all 20 nails. In some cases, leukonychia totalis has been associated with various other abnormalities or syndromes. Treatment may focus on the underlying cause when it is associated with another condition.

The condition is usually inherited, following either an autosomal dominant or autosomal recessive inheritance pattern. These inherited forms can be caused by mutations in the PLCD1 gene.

In some cases, leukonychia occurs in association with other underlying abnormalities or syndromes. Conditions that have been reported include palmoplantar keratoderma; certain types of cysts; severe keratosis pilaris; pili torti; hypotrichosis (lack of hair growth); onychorrhexis (brittle nails); koilonychia (spoon-shaped nails); Bart-Pumphrey syndrome; and Buschkell-Gorlin syndrome, when it occurs with sebaceous cysts and kidney stones. It has also reportedly been associated with typhoid fever, leprosy, cirrhosis, nail biting, trichinosis, and cytotoxic drugs (drugs that are toxic to cells). In a few cases, the cause of leukonychia is unknown (idiopathic).

Autosomal dominant inheritance means that having a change (mutation) in only one copy of the disease-causing gene is enough to cause signs or symptoms. When a person with an autosomal dominant condition has children, each child has a 50% (1 in 2) risk to inherit the mutated copy of the gene.

Autsomal recessive inheritance means that a person must have mutations in both copies of the disease-causing gene to have the condition. Usually, one mutated copy is inherited from each parent, who are each referred to as a carrier. Carriers of an autosomal recessive condition typically do not have any signs or symptoms.

There is no universally successful treatment for the whitening of the nails in people with leukonychia totalis. However, if the condition is known to have an underlying cause, treating that cause (when possible) may improve the condition.