Many local and systemic diseases reflect in nail abnormalities. Among these, nail discolorations are prominent. They may range from white to green.
Leukonychia is a term which refers to the white discoloration of the nails. It is derived from the Greek words “leukos” and “onyx”, which mean “white” and “nail”, respectively.
Fingernails closeup with the condition called leukonychia, white lines under the nail. Image Copyright: deepspacedave / Shutterstock
Leukonychia has been grouped in various ways depending on the criterion used.
1. One division uses the pathology underlying the discoloration.
- True leukonychia: the nail matrix is diseased, leading to abnormal coloration of the nail plate which emerges from it. The keratinocytes develop parakeratotic changes, with large keratohyaline granules. These reflect light completely, leading to the underlying pinkness of the vascular nail bed becoming invisible.
True leukonychia is usually due to systemic disease. It may be total or partial in extent, and is then called leukonychia totalis or partialis, respectively. The partial form is further divided into punctate, striate or distal leukonychias.
- Apparent leukonychia: the nail matrix is normal, but the nail bed is diseased in some way, altering the color of the overlying nail plate
- Pseudoleukonychia: the nail plate is diseased because of external factors such as fungal infection of the nail
2. Leukonychia has also been classified by the way it develops, whether congenital or acquired.
- Familial or hereditary leukonychia totalis: this rare disorder may be inherited in an autosomal dominant or recessive fashion, more commonly the former. In many cases, the responsibility for the defect lies with the mutation in the PLCD1 gene on chromosome 3p21.3-p22. This gene encodes for one subunit of a phospholipase enzyme which is vital to the process which controls the growth and color of the nails.
- Familial leukonychia totalis may be part of a syndromic illness, such as:
- leukonychia totalis associated with multiple sebaceous cysts and renal stones
- leukonychia totalis associated with deafness and knuckle pads
- leukonychia totalis associated with keratoderma and hypotrichosis
- Acquired leukonychia totalis: this is secondary to certain systemic illnesses such as:
- Cirrhosis of the liver
- Chronic kidney failure
- Congestive heart failure
- Diabetes mellitus
- Longstanding hypoalbuminemic states
- Hodgkin’s lymphoma
3. Classification of leukonychia by its distribution was first done by Unna.
- Leukonychia punctata: specks of whiteness on the nails
- Leukonychia striata: stripes or bands of whiteness across the nails
- Leukonychia totalis: the whole nail is pearly white or marble white
- Leukonychia partialis: the distal part of the nail turns white. This is considered at present to be an earlier phase of leukonychia totalis rather than a distinct entity. Both forms of leukonychia may occur on different fingers of the same person, and in different members of the same family, and appear to share a common family history.