Introduction

The nail matrix is a specialised tissue found at the base of the nail beneath the cuticle, also known as the proximal nail fold. It's a crucial part of the nail apparatus responsible for the production of keratinocytes, the primary cells contributing to nail growth. This area is densely packed with actively dividing cells, creating new nail tissue that contributes to the formation, growth and overall health of the nail. The nail matrix consists of several layers of epithelial cells that undergo continuous proliferation, leading to the generation of new nail material. As these cells move forward, they gradually become keratinised, forming the hard, protective structure of the nail plate that we observe externally.^1,3

Nail matrix in dermatology

The nail matrix plays a fundamental role in maintaining the integrity and appearance of the nail. Any changes or abnormalities within the matrix can manifest as nail disorders, influencing the overall health and aesthetic appeal of the nails. These changes can be observed in the nail texture, colour and pattern of growth. The examination of the nail matrix and its associated structures provides valuable insights into an individual's overall health. Dermatologists and healthcare professionals routinely encounter patients presenting with nail-related concerns. Therefore, understanding the intricate mechanisms within the nail matrix aids in the accurate diagnosis, treatment and management of diverse nail conditions.^4,6

Anatomy of the nail matrix

The nail comprises several distinct components, including the nail plate, nail bed, nail matrix, cuticle, proximal and lateral nail folds and the hyponychium. The nail plate is the visible, hardened portion that extends beyond the fingertip or toe. It rests on the nail bed, which is rich in blood vessels and contributes to the nourishment of the nail. The nail matrix (also known as the lunula), located beneath the proximal nail fold, is the region responsible for nail growth,^3,5 and extends beneath the skin surface. It's positioned at the base of the nail, occupying a critical space where new nail cells are actively produced.

The nail matrix is primarily composed of specialised keratinocytes, which are rapidly dividing cells undergoing a process called keratinisation,^3,5 forming the nail plate. Within the matrix, the cells undergo differentiation, transforming from basal cells into mature, keratinised cells that constitute the nail plate. Melanocytes in this region also contribute to the pigmentation of the nail.

Nail growth occurs as a result of the continuous proliferation and differentiation of cells within the nail matrix.⁵ As new cells are produced, they push older cells forward, forming the nail plate. The matrix acts as the 'root' of the nail, producing the cells that gradually harden and elongate, contributing to the visible part of the nail. Various factors such as age, health conditions, nutritional status, and external trauma can affect the rate and quality of nail growth by influencing the cellular activities within the matrix.^{3, 5,6}

Physiology of the nail matrix

The intricacies of the nail growth cycle, the impact of various factors, and the role of blood supply and nutrition are crucial in assessing and addressing conditions related to nail health and disorders. This information is essential in the diagnostic evaluations and the development of effective treatment strategies for nail-related concerns. The active growth phase, where cells in the nail matrix rapidly divide, leading to the production of new nail cells, is called the ‘Anagen phase’. This phase accounts for the majority of the nail growth and can last from a few weeks to several months, depending on individual factors. The ‘Catagen Phase’ is a transitional phase where nail growth slows down as cell division decreases. This phase is relatively short compared to the anagen phase. The ‘Telogen Phase’ is the resting phase where nail growth temporarily stops. Existing nail cells remain in place until new cells are generated in the subsequent anagen phase and push them forward.^5,7

Factors affecting nail growth

Blood supply and nutritional status 

The blood supply and nutritional status significantly influence the function of the nail matrix. A well-balanced diet and adequate blood circulation ensure the delivery of essential components necessary for robust nail growth and maintenance.⁷

Certain health conditions like malnutrition, hormonal imbalances and systemic diseases can affect the nail growth cycle, potentially causing irregularities or slowed growth. Nail growth tends to slow with age due to reduced metabolic activity and changes in cellular turnover. Trauma, injury, and environmental conditions can also impact nail growth and health. For instance, excessive exposure to water or harsh chemicals may weaken the nails.⁷

Clinical assessment and diagnostic procedures 

Essential nutrients like proteins, vitamins (especially B-complex vitamins), minerals (such as iron and zinc) and fatty acids are vital for maintaining healthy nails. These nutrients contribute to the production of keratin and support the overall health of the nail matrix. Deficiencies can lead to brittle, slow-growing or discoloured nails.^{7, 8}

Nail matrix disorders and pathologies

Onychomycosis refers to a fungal infection of the nail apparatus, including the nail matrix, bed or plate. It's caused by various fungi, typically dermatophytes, yeast, or moulds.¹⁰ It is recognised by thickening, discolouration (yellowing or white patches), crumbling and distortion of the nail. It may cause discomfort or pain in severe cases.^10,11,13 Diagnosis involves clinical examination, microscopy, and possibly culture tests. Treatment ranges from topical antifungal agents to oral medications or, in severe cases, surgical interventions like nail avulsion or laser therapy.^8,10

Leukonychia refers to white spots or streaks on the nails. It can result from various factors, including minor trauma to the nail matrix or underlying systemic conditions. There are two types - ‘true leukonychia’ (caused by matrix damage) and ‘apparent leukonychia’ (arising from abnormalities in the nail plate). True leukonychia usually doesn't require treatment, while apparent leukonychia may resolve when the underlying cause is addressed.^12,14

Beau's lines are transverse depressions or ridges that traverse the nail horizontally. They occur due to temporary disruptions in nail growth, often associated with systemic illnesses, severe stress, trauma or conditions affecting the nail matrix. These lines may indicate the timing of the insult to the matrix; each line represents a distinct episode of disruption in nail growth. The treatment of this condition focuses on addressing the underlying cause, and the lines tend to grow out over time as the nail regenerates.^15,16

Nail matrix pathologies and associated conditions

Psoriasis can affect the nail matrix, leading to various changes in the nails, including pitting, crumbling, discoloration and thickening. Nail psoriasis often accompanies skin psoriasis and can cause significant discomfort. Diagnosis involves a clinical examination and, sometimes, a biopsy. Treatment includes topical therapies, systemic medications and targeted therapies.

The formation of a dark pigmentation of the nail, often appearing as a brown or black longitudinal band is also referred to as melanonychia. It can result from various causes, including benign conditions, trauma, medications or more concerning conditions like melanoma.

Differentiating between benign and malignant causes is essential. Dermoscopy and biopsy may be necessary for accurate diagnosis. Management or treatment depends on the underlying cause; benign cases may not require intervention, while malignant conditions need prompt medical attention and appropriate management.^17,18

Clinical assessment and diagnosis procedures

In most cases physical examination and/or visual inspection of the nails is the first step for checking abnormalities in colour, texture, shape, thickness and presence of any nail lesions or irregularities. Dermoscopy can also be used; the dermatoscope magnifies and examines the nails, allowing for a detailed assessment of nail features and structures. Nail clippings or scrapings can be collected for microscopic evaluation to identify fungal or bacterial infections, helping diagnose conditions like onychomycosis. Culturing samples is used to identify specific pathogens causing nail infections.

X-rays or MRI is sometimes used in specific cases to evaluate underlying bone or soft tissue involvement, especially in severe nail disorders or trauma.¹⁹

Nail matrix biopsies are rarely performed but may be necessary in certain cases, especially when malignancy or atypical presentations are suspected. There are also emerging technologies, such as high-resolution dermoscopy or confocal microscopy for detailed examination of nail structures and pathologies at a microscopic level, and the utilisation of Optical Coherence Tomography (OCT) for non-invasive imaging of nail anatomy and pathology, offering valuable insights into nail matrix disorders.^18,19

Accurate diagnosis in nail matrix disorders is important for a precise diagnosis and enables the selection of appropriate treatment strategies, whether it involves topical antifungals for onychomycosis, targeted therapies for psoriasis or surgical interventions for severe cases and can prevent potential complications or spread to other nails or deeper tissues. Accurate diagnosis also helps avoid unnecessary treatments or interventions that might not address the underlying cause or could exacerbate the condition. A precise diagnosis allows for better monitoring of the condition's progress and appropriate follow-up to ensure treatment effectiveness, as well as enabling healthcare providers to educate patients about their condition, prognosis and necessary lifestyle modifications, fostering better compliance and understanding.^18,20

Treatment approaches

The treatment approach for nail matrix disorders varies based on the underlying condition, severity and patient-specific factors. Conservative measures encompass topical or oral medications, lifestyle modifications and proper nail care practices.

Topical Treatments, such as antifungal medications and steroid creams, are available for individuals to choose from. Steroid creams are used in conditions like nail psoriasis to reduce inflammation and symptoms. Oral antifungals like terbinafine or itraconazole for severe or widespread onychomycosis^11,20,21

Systemic therapies for conditions affecting the nail matrix, including psoriasis or autoimmune disorders. Proper nail trimming and maintenance to prevent further damage or complications. Individuals are advised to avoid activities that could harm the nails while making sure to eat a balanced diet rich in nutrients that support nail health and minimising exposure to harsh chemicals or excessive moisture that can weaken nails.^11,20,21

Nail matrixectomy is the partial or complete removal of the nail matrix to treat chronic or severe nail conditions like chronic ingrown nails or recurrent infections. It involves removing a part or the entire nail matrix using various techniques like chemical cauterisation, laser ablation, or surgical excision. Severe ingrown nails, chronic infections, or trauma that affects the nail matrix^11,20,21

Nail avulsion is also a procedure that involves the partial or complete removal of the nail plate or affected portion to allow for better access to underlying conditions or to alleviate pain.

Nail reconstruction is the reconstruction of the nail plate using artificial materials or grafts in cases of severe nail deformities or loss.^11,20,21

Conclusion 

The nail matrix plays a crucial role in nail health and growth. This small but complex structure is the cornerstone of nail production and maintenance, making it a key focus in dermatological studies and treatments. A thorough understanding of nail matrix anatomy and function is vital for healthcare professionals dealing with nail disorders.

Various conditions can affect the nail matrix, ranging from fungal infections to psoriasis. These disorders often manifest in visible changes to the nail, impacting both appearance and functionality. Proper diagnosis is essential, and modern techniques such as dermoscopy and optical coherence tomography have greatly improved our ability to assess nail matrix health.

Frequently asked questions

What causes changes in nail shape?

The changes in nail shape can result from various factors, including trauma, genetic predispositions, underlying health conditions, or systemic diseases affecting the nail matrix.

Can nutritional deficiencies affect the nail matrix?

Yes, deficiencies in essential nutrients like protein, vitamins (especially B-complex vitamins), minerals (such as iron and zinc) and fatty acids can impact the health of the nail matrix, leading to brittle, weak or discoloured nails.

How long does it take for a nail to grow from the matrix to the fingertip?

The average rate of nail growth from the nail matrix to the fingertip is around 3 to 4 millimetres per month for fingernails and slightly slower for toenails.

What are the potential complications of untreated nail matrix disorders?

Untreated nail matrix disorders can lead to chronic pain, recurrent infections, nail deformities, or in severe cases, damage to the surrounding tissues.

Is nail psoriasis primarily a result of nail matrix involvement?

Nail psoriasis can affect various parts of the nail apparatus, including the matrix, nail bed, or plate.

Matrix Involvement can cause changes such as:

• Thickening of the nail 
• Discolouration (yellowing or white patches)
• Crumbling 
• Distortion of the nail 

Can trauma to the nail matrix cause permanent damage?

Trauma to the nail matrix can result in temporary or permanent damage, depending on the severity. Severe or repeated trauma can sometimes lead to lasting changes in nail growth or appearance.

Are there any natural remedies that promote nail matrix health?

Maintaining a balanced diet rich in essential nutrients, proper hydration, and minimising exposure to harsh chemicals or excessive moisture can support overall nail health, including the nail matrix.

Can nail matrix disorders be prevented?

While some nail matrix disorders may not be entirely preventable, practising good nail hygiene, avoiding trauma, protecting nails from harsh chemicals, and maintaining a healthy lifestyle can reduce the risk of certain conditions.

Is it normal to have ridges on nails?

Low ridges on nails are generally considered a normal part of ageing. However, deep or prominent ridges could indicate underlying health conditions and should be evaluated by a healthcare professional.

How can one differentiate between benign and malignant causes of melanonychia?

Differentiating between benign and malignant causes of melanonychia often requires a detailed examination, including dermoscopy, biopsy, and sometimes additional imaging studies to assess the characteristics of the pigmented band and its surrounding structures. Consulting a dermatologist is crucial for accurate diagnosis and management.