Mammals use their nails as weapons, as primitive tools, for grooming purposes, for scratching, and for the removal of infestations. Humans use their fingernails to help pick up small objects and to scratch itchy skin. As with fingernails, the toenails are in constant contact with and exposed regularly to contactants and trauma. Fingernails protect vulnerable fingertips; toenails protect toes from the impact of footwear and external trauma. Nails are also important contributors to the aesthetic appearance of the hands and feet.

Inflammatory disorders that involve the nail matrix (root), such as psoriasis and eczema, can result in distinctive deformities of the nails. To the health care provider, nails may represent clinical findings of a skin disorder or be a signal to an underlying systemic disease.


Longitudinal Ridging (Onychorrhexis)

Brittle Nails (Onychoschizia)


Distinguishing Features

  • The separated portion is white and opaque, in contrast to the pink translucence of the attached portion. Normal physiologic onycholysis is seen at the distal free margin
    of healthy nails as they grow. Onycholysis is most frequently seen in women, particularly in those with long fingernails

External Causes

  • Irritants such as nail polish, nail wraps, nail hardeners, artificial nails, the use of fingernails as a tool, and habitual finger sucking. The toenails are subject to athletic injuries and from wearing tight shoes

  • Fungal infections such as chronic paronychia and onychomycosis (see below)

  • Certain drugs can act as phototoxic agents to induce fingernail onycholysis. Such drugs include diuretics, sulfa drugs, tetracycline, minocycline, and doxycycline. Hemorrhagic onycholysis may result from taxanes, a chemotherapeutic agent used in the treatment of various cancers

Internal Causes

  • Psoriasis is the most common inflammatory cause of onycholysis. Often there is evidence of psoriasis elsewhere on the body or there may be other psoriatic nail findings such as pitting, subungual hyperkeratosis, and “oil spots” (see Psoriatic Nail Dystrophy below)

  • Inflammatory skin diseases of the nail matrix (root), such as eczematous dermatitis or lichen planus

  • Thyroid disease, pregnancy, and anemia have been reported as potential associations

Green Nail Syndrome


Clinical Variants

Distal subungual onychomycosis accounts for more than 90% of all cases and is characterized by the following.


  • Nail thickening and subungual hyperkeratosis (Fig. 15-5) (scale buildup under the nail)

  • Nail discoloration (yellow, yellow-green, white, or brown)

  • Nail dystrophy

  • Onycholysis (nail plate elevation from the nail bed)

  • Frequently associated with chronic palmoplantar tinea (i.e., “two feet, one hand” variant of tinea) (see Fig. 14-19)


  • May affect one or more toenails, most often the great toenail (Fig. 15-6) or the fifth toenail

  • Generally asymptomatic, aside from footwear causing occasional physical discomfort and the psychosocial liability of unsightly nails, onychomycosis can be a source of seeding for bacterial infection leading to cellulitis, especially in diabetics

  • Toenail onychomycosis is cured less quickly and effectively than in the fingernails

In superficial white onychomycosis, the fungus is located in the upper level of the nail plate (Fig. 15-7).

In proximal white onychomycosis, HIV infection should be suspected (Fig. 15-8).

Jan 8, 2023 | Posted by in Dermatology | Comments Off on Nails

Full access? Get Clinical Tree

Get Clinical Tree app for offline access