Diagnosis
In countries where people are frequently infected, a person is considered to have leprosy if they have one of the following two signs:

Skin lesion consistent with leprosy and with definite sensory loss. Positive skin smears.Skin lesions can be single or many, and usually hypopigmented, although occasionally reddish or copper-colored. The lesions may be flat (macules), raised (papules), or solid elevated areas (nodular). Experiencing sensory loss at the skin lesion is a feature that can help determine if the lesion is caused by leprosy or by another disorder such as tinea versicolor. Thickened nerves are associated with leprosy and can be accompanied by loss of sensation or muscle weakness, but muscle weakness without the characteristic skin lesion and sensory loss is not considered a reliable sign of leprosy.In some cases, acid-fast leprosy bacilli in skin smears are considered diagnostic; however, the diagnosis is typically made without laboratory tests, based on symptoms. If a person has a new leprosy diagnosis and already has a visible disability caused by leprosy, the diagnosis is considered late.In countries or areas where leprosy is uncommon, such as the United States, diagnosis of leprosy is often delayed because healthcare providers are unaware of leprosy and its symptoms. Early diagnosis and treatment prevent nerve involvement, the hallmark of leprosy, and the disability it causes.There is no recommended test to diagnose latent leprosy in people without symptoms. Few people with latent leprosy test positive for anti PGL-1. The presence of M. leprae bacterial DNA can be identified using a polymerase chain reaction (PCR)-based technique.
This indicates that the defective gene responsible for a disorder is located on an autosome (chromosomes 12 and 17 are autosomes), and only one copy of the defective gene is sufficient to cause the disorder, when inherited from a parent who has the disorder. Diagnosis
Differential diagnosis
It is often mistaken for leukoplakia.The differential diagnosis also includes hyperplastic candidiasis and frictional keratosis

Classification
The ICD-10 lists WSN under "other congenital malformations of mouth". It could be classified as a skin condition, or more precisely as a genodermatosis (a genetically determined skin disorder). Treatment
There is no treatment, but because this is a benign condition with no serious clinical complications, prognosis is excellent. See also
Oral melanosis
List of cutaneous conditions caused by mutations in keratins
Hereditary benign intraepithelial dyskeratosis

References
External links
White sponge nevus of cannon; Leukokeratosis, hereditary mucosal at NIHs Office of Rare Diseases