Transverse Leukonychia (Mees’ Lines)
A 30-year-old man visited the hematology clinic reporting a 4-month history of white lines appearing on his fingernails. About five months earlier, he had been diagnosed with primary mediastinal large B-cell lymphoma and had started receiving systemic chemotherapy. The nail changes began to manifest midway through his six cycles of treatment. During the physical examination, six transverse white lines were observed on the nails of both hands. The diagnosis of transverse leukonychia, also known as Mees’ lines, was established. Mees’ lines develop due to abnormal keratinization of the distal nail matrix. In this case, each of the patient’s six chemotherapy cycles was believed to correspond to a band of leukonychia.
Mees’ lines can be distinguished from Muehrcke’s lines, which are a type of apparent leukonychia resulting from vascular changes in the nail bed, by the fact that Mees’ lines do not blanch. Furthermore, Mees’ lines are smooth, setting them apart from Beau’s lines, which are transverse depressions in the nail bed caused by an interruption in nail matrix growth. The patient was reassured about the benign nature of these nail changes. By the 10-month follow-up, the nail alterations had disappeared.
Changes in nail colour can offer valuable insights into underlying systemic and skin conditions
Specifically, white discoloration (leukonychia) is quite common and can stem from various causes, ranging from simple manicure practices to severe conditions like liver or kidney failure. Therefore, a thorough evaluation of patients with leukonychia is crucial. Historically, two classifications have been proposed for leukonychia. The morphological classification categorizes nail changes based on the pattern of white lines: total, partial, transverse, and longitudinal leukonychia. Examples of transverse leukonychia include Mees’ and Muehrcke’s lines, while Terry’s and Lindsay’s nails exemplify total and partial leukonychia. On the other hand, the anatomical classification distinguishes based on the structure responsible for the white coloration: the nail plate in true leukonychia, the nail bed in apparent leukonychia, and only the surface in pseudoleukonychia. This review integrates both morphological and anatomical aspects into an algorithm, offering clinicians an efficient and effective approach to managing leukonychia.
Newton’s theorem and transverse leukonychia
According to Newton’s theorem, a surface appears white when it reflects all visible light radiation. In true leukonychia, the nail plate surface appears white due to its diffuse reflection of visible light, concealing the vascularized nail bed beneath. This phenomenon arises from abnormal keratinization in the distal matrix, leading to persistent parakeratosis with irregularly shaped onychocytes and perinuclear vacuolization. Keratohyaline granules are also found in the intermediate and ventral nail plates. Electron microscopy reveals dissociated, fragmented, and irregularly aligned keratin fibres.
Parakeratosis can result from various factors that damage the distal nail matrix. Once the triggering factor ceases or is removed, the white colouration begins to grow out as new nail forms. In contrast, apparent leukonychia’s white appearance stems from compression of the nail bed’s blood vessels. Histologically, chronic anaemia, thickened capillary walls, altered subungual keratin, or increased connective tissue growth between the nail and bone contribute to this phenomenon. Localized or general nail bed oedema can compress and constrict subungual vasculature, affecting collagen fibre organisation.
Eliminating the causative factor initiates resolution distally and progresses proximally, opposite to true leukonychia. This is attributed to capillary blood pressure variations along the nail bed, with slightly higher pressure distally aiding in overcoming resistance and resolving the white area first.
Pseudoleukonychia occurs when an external factor disrupts the normal attachment of nail plate onychocytes, compromising the transparency of the nail plate. This leads to scaling of the upper layers of the nail plate, causing light reflection. Unlike other causes of leukonychia, pseudoleukonychia can be distinguished by the ease of scraping off the white powdery material from the affected nail plate.
Management
Management of patients with leukonychia hinges entirely on addressing the underlying cause. Acquired leukonychia is typically treated by addressing the root issue. For punctate true leukonychia, gentle nail care is emphasized, such as avoiding cuticle manipulation and minimizing exposure to irritating grooming products like nail polish, artificial nails, or nail glue. Regular moisturizing can also be helpful. Trauma avoidance is crucial as it’s a common cause of transverse and punctate true leukonychia. In cases of pseudoleukonychia caused by fungal infections, antimycotic therapy is often prescribed. Management of other localised skin and systemic disorders contributing to leukonychia is beyond the scope of this discussion and may necessitate referral to a specialist when systemic issues are suspected.
A thorough evaluation of patients with leukonychia is crucial due to the diverse range of potential causes contributing to the abnormal nail colour, spanning from minor manicure practices to severe conditions like liver or kidney failure. This publication introduces a simple diagnostic algorithm that integrates both morphological and anatomical classifications. This approach aims to assist clinicians in effectively managing this prevalent color abnormality.
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