All cells and tissues of the nail apparatus can give rise to neoplastic lesions. Given the special anatomy of the nail apparatus, symptoms, and ungual signs of these tumors, they may look similar to other different nail diseases, making difficult the clinical diagnosis. Nail tumors cause nail deformation and partial or total destruction of the nail plate owing to the chronic pressure on the matrix or the nail bed. Nonmelanocytic nail tumors can be divided into epithelial, soft tissue, bone, pseudo, and metastatic tumors. In this chapter we present a review of the most frequent nonmelanocytic tumors of the nail apparatus.

Disorders involving the nail unit are common in both the primary care and the dermatology clinic. By virtue of the nail unit’s unique anatomy, procedural complexity can range from nail clipping to microsurgery. Providers should be aware of the range of procedures available in the diagnosis and management of various pathologies. In this chapter, we review common nail procedures within the armamentarium of the general dermatologist, including indications, techniques, and special considerations for each.

Nail cosmetics are becoming increasingly popular with continuous development of new technologies that have really affected the global market. Nail products, such as nail polish, nail polish removers, and artificial nails, have shown to have some adverse effects that can involve not only the nail but also the skin, with contact allergy being a very common problem. Manicure technique can also cause nail and periungual damage. This chapter discusses properties and most common side effects of manicure and nail cosmetics.

The nail has a unique structure and function and is an integral part of the distal digit tip. Understanding the anatomy, development, physiology, and function of the nail as a whole and its individual subunits is helpful to the clinician to aid assessment of the patient, diagnosis, and treatment. Abnormalities in the nail unit can be seen in both systemic and localized pathology and may result in functional and cosmetic problems for the patient.

Self-induced disorders of the nail are relatively poorly understood, with few citations in both the dermatology and mental health professions literature. Although self-induced disorders are typically categorized as a subset of traumatic nail abnormalities, they are distinctly characterized by an individual patient's own manipulation of the nail unit. Clinical findings, although sometimes nonspecific, may be easily recognized, especially when paired with appropriate screening questions. Evidence-based treatments are limited, although behavioral therapy currently seems to hold more promise than pharmacologic intervention.

Prevalence of nail psoriasis ranges from 7% to 56%, in psoriatic patients and significantly burdens quality of life. Nail psoriasis is often associated with psoriatic arthritis. Clinical features present due to inflammation of either the nail matrix or the nail bed and include pitting, leukonychia, red spots in the lunula, crumbling, onycholysis, splinter hemorrhages, subungual hyperkeratosis, and oil-drop salmon patches. Management of nail psoriasis should be individualized, and this depends on the number of nails affected, involvement of skin and/or joints, that might affect the choice of topical or systemic therapies.

The incidence of nail conditions in pediatric population is influenced by hereditary, social, and environmental factors. Many conditions are less common than in adults and they differ in clinical aspects, diagnostic approach, and management, while others manifest mainly or exclusively in children. In this chapter, we classify nail diseases in pediatric population by dividing the disorders according to the age group in which they appear in most of the cases:

Nail disorders account for about 10% of all dermatologic cases and are largely prevalent in older individuals. The geriatric population is at an increased risk for nail disorders because of an amalgam of factors, including the natural aging process, altered biomechanics, and dermatologic or systemic diseases as well as their treatments. Common clinical manifestations of the aged nail unit include altered chemical composition, histology, nail growth, nail color, contour, surface texture, and thickness. Additionally, age-related nail dystrophies such as brittle nails, onychomycosis, onychauxis, onychogryphosis, onychoclavus, onycholysis, onychocryptosis, splinter hemorrhages, subungual hematomas, and subungual exostosis are among the most common nail conditions in the elderly. Because of the possibility of pain, serious symptoms, impairment of daily activities, and the psychologic burden of asymptomatic nail changes, it is of value for practitioners to be aware of the signs and symptoms of nail disorders in the elderly. A knowledge base pertaining to this topic may facilitate improved assessment, diagnosis, and management of the various onychodystrophies encountered by this subset of the population.

Ingrown toenail, or onychocryptosis, most commonly affects young adults and the great toenail. Many anatomic and behavioral factors are thought to contribute to this discomfort condition, such as improper trimming, repetitive or inadvertent trauma, genetic predisposition, hyperhidrosis, and poor foot hygiene. Surgical treatments rely on two main approaches: narrowing of the nail plate and debulking of the soft tissues. Phenolization of the lateral matrix horn is one of the safest, easiest, and most commonly performed method with low recurrence rate.

Nail dermoscopy (onychoscopy) is a versatile tool that is relatively new to the practice of dermatology. The goal of onychoscopy is to improve diagnostic skill in nail disorders. This chapter covers the technique and current knowledge of features observed in various nail disorders of inflammatory, traumatic, infectious, and neoplastic origin. Dermoscopy can also be utilized during nail surgery to select optimal biopsy site as well as excisional margins.