Musculoskeletal
Medicine for Medical
Students
Disorders of the nail
Author: Joseph Bernstein Version: 17
Date: 24-Mar-2014 15:09
Table of Contents
1 Description 4
2 Structure and function 5
38
3.1 Trauma 8
3.2 Infections 11
4 Malignant tumors 15
5 17
5.1 Nail manifestations of systemic disease 17
6 Clubbing is an increased curvature of the nail and
nail fold in a proximal to distal direction, often with
the appearance of a bulbous fingertip (Figure 9). The
nail plate often has a shinny appearance. This is
frequently a manifestation of systemic disease, with
cardiac, pulmonary, and gastrointestional conditions
being the most common, although it can occur without
underlying etiology. The mechanism by which this occurs
has not been clearly elucidated. 18
7 Red flags 20
7.1 Trauma 20
7.2 Infection 20
7.3 Tumor 20
8 Miscellany 21
9 Key terms 22
10 Skills and competencies 23
1 Description
The fingernail serves multiple functions. In addition to protecting the fingertip, it provides
tactile sensation, aids in thermoregulation, and assists in picking up small objects; it also
has dense lymphatics in the hyponychium that help resist infection. The fingernail is the
most frequently injured portion of the finger secondary to its prominent location. The nail
is also susceptible to infection and may be the site of tumors, both benign and
malignant. Last, the nail may display signs of underlying systemic disease.
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2 Structure and function
The nail is a plate of keratin that covers the dorsal aspect of the distal phalanges of the
fingers and toes.
The anatomy of the nail is shown in figures 1 and 2.
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(modified from http://www.aafp.org/afp/2008/0201/afp20080201p339-f1.gif and
wikipedia, respectively)
The nail plate (which, in layman’s terms, is the “nail” itself) is a hard sheet of translucent
keratin in which lie several layers of dead, compacted cells.
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The nail bed is the tissue that lies beneath the nail plate. The nail bed contains nerves,
lymphatics and capillaries. (These capillaries are used to assess “capillary refill” by
compressing the nail to momentarily occlude them, and then releasing the pressure to
allow them to “refill”.)
Within the nail bed is the germinal matrix, the source of cells that become the nail plate.
As these cells are produced, older cells are pushed forward and compressed, giving rise
to the typical growing pattern of the nail.
A small piece of the matrix, the lunula (so named because it is white and crescentshaped, like a “little moon”) is often visible at the proximal most aspect of the nail.
The eponychium is a small band of epithelium that covers the proximal aspect of the
nail; the paronychium is a similar border tissue around the medial and lateral borders.
The cuticle is a layer of epidermis that folds back over the surface of the nail plate at its
base.
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3
3.1 Trauma
Trauma to the nails is common, with the middle finger being most commonly affected
due to its length and greater exposure compared to adjacent shorter digits. There are
often associated fractures of the distal phalanx.
Mild trauma may result in a painful subungual hematoma: a collection of blood
compressed between the nail plate and the nail bed on the distal phalanx. (Figures 3a).
Figure 3a
Treatment involves placing a hole in the nail plate to relieve the pressure, as shown in
the figure (replace with photo?)
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If the subungual hematoma involves more than 50% of the nail, the nail plate is generally
removed and the nail bed repaired with fine absorbable sutures (Figure 3c).
Figure 3c
Nailbed lacerations are often the result of crush injuries, producing a stellate laceration
pattern. These injures require repair. Without adequate repair (and some times despite
best efforts) a cosmetic defect results. Malformations after healing can also be painful.
Because nailbed lacerations are typically crush injuries, x-rays should always be
obtained to exclude a fracture.
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In children, it may be possible to repair the nailbed with a cyanoacrylate adhesive (eg,
"Dermabond") with a cosmetic outcome comparable to that of suture repair. This option
is advantageous in the pediatric population specifically because it avoids keeping the
child motionless and is relatively pain-free.
A hook nail deformity is a condition that results following amputation of the soft tissues
and the tuft of the distal phalanx (Figures 4a-b}. The nail bed has lost the distal support
and the nail grows downward around the tip of the finger. This is prevented by avoiding
sutures in the distal nail bed and ensuring adequate bony support for the nail bed
following traumatic injuries.
Figure 4a
Figure 4b
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3.2 Infections
The nail is a site for both acute and chronic infections. Acute infections often result from
a minor event, such as a superficial laceration or pulling a hangnail, with bacteria —
typically Staphylococcus and Streptococcus — being the most common etiology.
Chronic infections are typically fungal and may result from multiple acute infections
treated with antibiotics or chronic moisture, with Candida being the most common
etiology. Less commonly, atypical organisms, such as Mycobacterium, are the source of
infection. These atypical infections are usually encountered in the setting of
immunocomprised states.
Paronychia (a collection of pus between the nail plate and the nail fold) and felons (a
purulent collection forms on the palmar surface of the distal phalanx) are discussed in
detail in the chapter on hand infections
Herpetic whitlow is a viral lesion caused by the Herpes simplex virus and involves the
paronychium. Prior to use of gloves by dental and medical professionals, this was seen
in workers around oral secretions. It is currently more commonly seen in children who
suck their thumb or fingers or in adults following contact with infected genitals. Initially,
this has the appearance of an acute bacterial infection, but clear vesicles will eventually
develop, helping differentiate this from an acute infection. The process is self-limiting,
and incision and drainage should be avoided as a subsequent bacterial infection may
occur, prolonging the time for resolution and often requiring additional treatment.
photo of Herpetic whitlow of the hand
Onychomycosis (ie, fungal infection of the nail) occurs more in toenails than in
fingernails, but can be found in the latter. Diabetes, vascular problems or
immunocompromised states are risk factors. Nail fungus can cause three problems (in
order of frequency): cosmetic deformity, pain, and systemic spread. Onychomycosis is
difficult to treat; recurrences are common. Oral medications such as terbinafine do not
uniformly clear the infection, and side effects as severe as liver damage may result.
Antifungal lacquers (eg Penlac) can help clear up some nail fungal infections but require
diligent use (with frequent debridement) for up to one year. Surgery or laser ablation
may also be employed.
photo of Onychomycosis hand Benign tumors
Tumors of the nail bed, though relatively uncommon, require the physician to have a
heightened sense of awareness when a patient presents with pain or a change in the
appearance of the nail. The most common benign tumors associated with the nail
complex are mucous cysts (ganglion cysts), pyogenic granuloma, verucca, glomus
tumors, and benign melonychia.
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Ganglion cysts, more commonly referred to as mucous cysts in this location, are the
most common tumor affecting the nail bed (Figure X). They result from an arthritic spur,
or osteophyte, of the distal interphalangeal joint (DIP) of the fingers (or interphalangeal
(IP) joint of the thumbs). Depending on the location of the cyst, the nail may have
ridging, grooving or curvature, and the cyst may involve the eponychial fold. Treatment
should be directed at removal of the stalk of the cyst and the underlying spurs of the
joint. Nail deformities often improve following removal of the cyst. Because the cyst
originates in the joint (and communicates with it) rupture of the cyst through the skin may
introduce bacteria into the joint space
Figure X. Ganglion (mucous) cyst JB: a photo showing this in PROFILE (showing elevation
out of the plane of the photo) may be better
Pyogenic granuloma is a raised lesion that is a proliferation of granulation tissue; it is
frequently traumatized and bleeds. These lesions often develop when a wound has
failed to heal and persistent bleeding prompts presentation to the physician. Like the
Holy Roman Empire (which was said to be not Holy, Roman or imperial) pyogenic
granuloma may be completely misnamed: "pyogenic" suggests infection, incorrectly; and
there is no granuloma here either. Accordingly, the term Eruptive Hemangioma has been
suggested. Most pyogenic granulomata resolve spontaneously. Those that do not can
be removed with surgical excision or thermal ablation (eg electrocautery or freezing)
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FIGURE X+1 (from wikipedia)
Verruca vulgaris, or the common wart, may present around the perionychium. Multiple
treatment methods are available, without any proving to be superior. When the
eponychial fold is involved, permanent scarring may result.
Glomus tumor is a neoplasm of the smooth muscle cells of the glomus body, which
regulate blood flow and temperature in the finger (Figure 4). Half of these tumors occur
in the subungual area (and give rise to nail deformities). As might be expected with any
mass, glomus tumors can present with severe pain and point tenderness; the more
specific finding is focal cold sensitivity. MRI with gadolinium is helpful for diagnosis;
treatment involves excision of the mass.
Figure X+2. Glomus tumor; image courtesy of Peter Murray, MD
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Melonychia is a benign pigmented longitudinal streak in the nail bed (Figure 5). This can
be concerning for melanoma, and microscopic tissue evaluation is necessary for the
diagnosis. Biopsy is performed with a full thickness longitudinal incision following
removal of the nail plate. The nail bed is undermined and closed with fine absorbable
sutures.
Figure X+3. Melonychia of the nail bed
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4 Malignant tumors
Squamous cell carcinoma and melanoma are the most common malignancies of the nail
complex. Radiographs of the finger should be obtained to evaluate for osseous changes
of the distal phalanx.
Squamous cell carcinoma is responsible for approximately 20% of all cutaneous
malignancies, but is less common than melanoma in the subungual region. It may
present with early skin changes or more advanced lesions (Figures 6a-b). Treatment
typically involves amputation at the DIP joint of the finger (IP joint of the thumb).
Figure xxa. Squamous cell carcinoma of the finger
Figure xx-b. Squamous cell carcinoma of the thumb
Malignant melanoma accounts for 4% of cutaneous malignancies, but is responsible for
80% of the deaths from cutaneous malignancies. Approximately 2% occur in the hand,
and half of these are subungual. They may present as pigmented lesions in the nail bed
or in the surrounding eponychium (Figures 7a-b). Full-thickness biopsy of the lesion is
necessary to determine diagnosis and make treatment recommendations. Prognosis
depends on the depth of invasion and sentinel lymph node status. Lesions greater than
1 mm in thickness or involving the entire depth of the nail bed should have sentinel
lymph
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node biopsy to evaluate for metastatic disease. Surgical treatment of the finger typically
involves amputation proximal to the adjacent joint. Although Moh’s micrographic surgery
has been performed in some cases, reconstruction is challenging, often resulting in
worse functional outcomes than amputation.
Figures 7a. Malignant melanoma of the thumb
Figure 7b. Malignant melanoma of the finger
Metastatic disease can occur to the fingertip, with lung primary being the most common
primary source. About one third of the time, this is from an undiagnosed primary tumor
and may mimic an infection.
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5
5.1 Nail manifestations of systemic
disease
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Disorders of the nail
6 Clubbing is an increased
curvature of the nail and
nail fold in a proximal to
distal direction, often
with
the appearance of a bulbous
fingertip (Figure 9). The
nail plate often has a
shinny
appearance. This is
frequently a manifestation
of
systemic disease, with
cardiac, pulmonary, and
gastrointestional
conditions
being the most common,
although it can occur
without
underlying etiology. The
mechanism by which this
occurs has not been clearly
elucidated.
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Figure 9. Clubbing of the fingers
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7 Red flags
7.1 Trauma
crush injuries to the nailbed are associated with distal phalanx fractures
subungal hematomas greater than 50% of the nail should be evacuated to relieve
pressue
7.2 Infection
fingernail infection with fungus may be a sign of diabetes, circulatory disorders a
weakened immune system dysfunction.
ruptured mucous cysts communicate with the joint space
7.3 Tumor
Beware of melanoma!
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8 Miscellany
Patients of most vocations and avocations can perform functionally well following injury
or amputation of a fingertip. In fact, an article entitled Less than ten - surgeons with
amputated fingers in the Journal of Hand Surgery describes multiple physicians and
surgeons who continue to practice following amputations of a digit.
Fingernails grow approximately 2 inches per year
Fingernails do NOT grow after death; rather, the surrounding skin retracts, giving that
illusion
Illicit drugs can be identified in nail clippings up to 8 months after last usage (and unlike
hair test, which can be subverted by head-shaving, nail testing is much less likely to be
undermined by completely removing the nail).
The first syllable in the word “hangnail” does not refer to the nail “hanging” from the
finger; rather, it’s root is ang, meaning pain (similar to the word “anguish”)
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9 Key terms
Fingernail, fingertip, perionychium, nail bed, subungual, mucous cyst, glomus tumor
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10 Skills and competencies
Recognize both traumatic and acquired conditions affecting the nail and perionychium
and have an understanding of treatment principles
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