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12 Skin Signs of Systemic Disease and Reactive Disorders of the Lower
Extremity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 71
12.1 Diabetic Dermopathy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 71
12.2 Erythema Multiforme . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 71
12.3 Erythema Nodosum . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 72
12.4 Granuloma Annulare . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 72
12.5 Idiopathic Guttate Hypomelanosis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 72
12.6 Leukocytoclastic Vasculitis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .73
12.7 Lipodermatosclerosis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 73
12.8 Necrobiosis Lipoidica . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 74
12.9 Perforating Folliculitis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 74
12.10 Porokeratosis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 75
12.11 Pretibial Myxedema . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 75
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 76
13 Ulcerations of the Lower Extremity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 77
13.1 Diagnosis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 77
13.1.1 Shape . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 77
13.1.2 Base . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 77
13.1.3 Peri-wound Skin . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 77
13.1.4 Location . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .77
13.2 Arterial Ulcers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 77
13.3 Diabetic Ulcers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 78
13.4 Venous Ulcers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 78
13.5 Pyoderma Gangrenosum . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 79
13.6 Sickle Cell Ulcer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 79
13.7 Calciphylaxis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 79
13.8 Pressure Ulcers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 80
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 80
Contents
14 Drug Eruptions of the Lower Extremity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 81
14.1 Morbilliform Drug Eruptions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 81
14.2 Fixed Drug Eruption . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 81
14.3 Acute Generalized Exanthematous Pustulosis . . . . . . . . . . . . . . . . . . . . . . . . . . . 82
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 82
15 Biopsy Techniques of the Lower Extremity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 83
15.1 Shave Biopsy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 83
15.2 Punch Biopsy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 84
15.3 Excisional and Incisional Biopsies . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 85
15.4 Curettage and Electrodesiccation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 86
15.5 Nail Biopsy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 87
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 88
16 Dermatologic Therapies of the Lower Extremity: Topical and Systemic . . . . . . . . 89
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 91
Index . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 93
Nail Disorders oftheLower Extremity
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The nail is an appendage of the skin that provides a protective barrier to the underlying distal phalanx and soft tissue
structures from trauma. Nail appearance and discomfort are
the motivators for patients to schedule a consultation.
Onychodystrophy is any alteration of nail morphology and
is caused by either exogenous or endogenous factors. One
of the most common types of toenail onychodystrophy is
onychomycosis which represents about half of nail pathologies; other conditions that may mimic dermatophyte
infection of the nail unit include psoriasis, lichen planus,
and trauma. This chapter will explore a range of disorders
that affect the nail.
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1.1 Nail Plate Changes
1.1.1 Beau’s Lines
Beau’s lines are transverse depressions in the nail plate that
originate within the matrix and progress distally as the nail
grows. They occur after a stressful event that temporarily
interrupts nail formation or mitotic function of the proximal
matrix.
Beau’s lines are the most common and least specic nail
change in systemic diseases. The margin is parallel to the
lunula when the cause is internal and is more apparent on
thumb and great toenails. The time of stress can be calculated after measuring the distance from the cuticle to the
lines. Multiple transverse lines indicate a repetitive or recurrent stressor. The depth of the depression represents the
extent of damage. If there is complete inhibition of nail
growth for around 2weeks, Beau’s line will reach maximum
depth resulting in onychomadesis [1].
Diseases associated with Beau’s lines include: cardiovascular (myocardial infarction, myocarditis, peripheral vascular disease); endocrine (diabetes mellitus, hypoparathyroidism,
thyrotoxicosis); hematologic (Hodgkin’s lymphoma); infec-
Fig. 1.1 Beau’s lines in the presence of onychomycosis on the great
toenail
tious (hand, foot, and mouth disease, Kawasaki disease,
measles, syphilis, mumps, sepsis); pulmonary (hypoxemia,
pneumonia, pulmonary embolism); renal (chronic renal failure); use of cytostatic drugs, high fever, exposure to extreme
cold, psychological stress, and poor nutritional status.
Idiopathic and inherited forms may also occur (Fig.1.1).
1.1.2 Onychomadesis
Onychomadesis results from an insult to the matrix and can
present with shedding of the nail or a proximal sulcus that
splits the nail plate into two parts. This condition is an
extreme expression of Beau’s lines, and the causes are the
same [1, 2]. In the toenails, trauma is often an inducing factor. The condition is best managed conservatively with treatment of any underlying cause and avoidance of trauma
(Fig.1.2).
© The Author(s), under exclusive license to Springer Nature Switzerland AG 2022
T. C. Vlahovic, S. M. Schleicher, Atlas of Lower Extremity Skin Disease, https://doi.org/10.1007/978-3-031-07950-4_1
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Fig. 1.2 Onychomadesis of the great toenail
1 Nail Disorders oftheLower Extremity
1.1.3 Onychorrhexis
Onychorrhexis refers to the longitudinal lines or depressions
of the nail plate. Onychorrhexis manifests as nail plate splitting, longitudinal thickening, or multiple splits leading to
triangular fragments at the nails’ free edge. Nail matrix
involvement leads to abnormalities in epithelial growth and
keratinization [3].
Among the various factors causing onychorrhexis are disorders of vascularization and oxygenation (such as anemia or
arteriosclerosis), as well as systemic and dermatologic diseases (disorders of cornication and inammatory diseases).
Onychorrhexis may also be caused by microtrauma to the
proximal nail fold. Raynaud disease, lichen striatus, and trachyonychia can lead to longitudinal splits. Filing of the nail
and application of nail hardeners may smooth and ll in the
gaps (Fig.1.3) [3].
1.1.4 Trachyonychia (Twenty Nail Dystrophy)
Trachyonychia is a descriptive term referring to rough nail
changes [4]. Trachyonychia can affect all nails, referred to as
twenty nail dystrophy. It is characterized by brittle, thin
nails, with excessive ridging. The excessive ridging causes a
rough, opaque appearance in the nails. The nails appear as if
they have been sandpapered. The cuticle is also hyperkeratotic and ragged. Twenty nail dystrophy may present as an
idiopathic disorder of the nails or it can be associated with a
Fig. 1.3 Onychorrhexis as viewed through a dermatoscope
Fig. 1.4 Trachyonychia of toenails 1–5
variety of other disorders such as including vitiligo, atopic
dermatitis, lichen planus, psoriasis, and alopecia areata.
1.2 Nail Shape andSize Changes
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Trachyonychia is a disease of the nail matrix, and a
pathological diagnosis requires a nail matrix punch or a
longitudinal nail biopsy. The disease is benign, and the
diagnosis is made clinically. There is no universally
accepted treatment for this chronic disorder. Treatments
such as topical or oral steroid treatments are for cosmetic
purposes. Treatment options include topical and intralesional steroids.
Twenty nail dystrophy may be present as an idiopathic
disorder of the nails or it can be associated with a variety of
other disorders such as vitiligo, atopic dermatitis, lichen planus, psoriasis, and alopecia areata (Fig.1.4).
1.2 Nail Shape andSize Changes
1.2.1 Anonychia
Anonychia is dened as the absence of all, one, or several
nails. It can be congenital or acquired and may be associated
with trauma, ichthyosis, lichen planus, infection, and contact
dermatitis. It may also be self-induced or iatrogenic (surgically induced).
Aplastic anonychia is a congenital disorder marked by
absence of nails at birth. In acquired nail atrophy, the damage
to nail unit progresses and no recognizable nail remains.
Hypoplasia of the nail occurs as complete absence of the nail
unit as seen on the thumb, index ngers, and toes of patients
with nail and patella absence syndrome, an autosomal dominant syndrome presenting at birth. Patients later develop
crippling degenerative joint disease and renal failure [5].
Diagnosis is conrmed by genetic testing. Camouage with
an articial nail or nail bed tattoo art improves cosmesis
(Fig.1.5).
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Fig. 1.5 Iatrogenic anonychia of toes 1, 2, and 4
1.2.2 Koilonychia (Spoon Nails)
Koilonychia, also known as spoon nails, presents as a longitudinally and/or transversely concave nail plate with everted
lateral edges. The nail may be thinned and brittle. The features are most prominent in the thumb or great toe, especially
in children. Spoon nails are attened or concave in the middle with laterally everted edges. Trachyonychia or onychomycosis may accompany koilonychia.
Spoon nails are often seen in the setting of inammatory
skin disease, onychomycosis, or secondary to anemia.
Associated diseases include lichen planus, psoriasis, iron
storage diseases such as hemochromatosis, and iron deciencies such as Plummer-Vinson syndrome. Other conditions
Fig. 1.6 Pincer nail on second toenail
include endocrine disorders such as hyper- and hypothyroidism, diabetes. Chronic renal failure, upper gastrointestinal
carcinomas, and repetitive trauma can also induce
koilonychia.
Diagnosis is based on clinical appearance. Topical or
injectable steroids, may improve the condition when secondary to psoriasis or lichen planus. When caused by iron related
disorders, the focus of treatment is on iron supplementation
[6]. In children the deformity may spontaneously regress
(Fig.1.6).
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1.2.3 Pincer Nails
Also known as a trumpet nail, pincer nails are the result of transverse overcurvature of the nail plate that increases distally along
the longitudinal axis. It most commonly affects the great toenail
and can arise secondary to nail psoriasis, underlying tumor, illtting shoes, and other biomechanical issues. Some cases are
hereditary. This condition is not the same as an ingrown nail. It
can be hereditary or acquired and may be painful.
Pincer nails are presumed caused by either lack of ground
reaction force on the digit or an increase in the automatic
curvature force. Lack of ground reaction force could result in
mismatched ventral and dorsal nail matrix growth resulting
in an inward curvature of the distal nail.
A pincer nail is a result of transverse overcurvature of the
nail plate that increases distally along the longitudinal axis.
It often affects the great toenail but can affect any nail. It may
appear as a result of nail psoriasis, underlying tumor, illtting shoes, and other biomechanical issues of the foot. It is
hypothesized that pincer nails may either be caused by the
lack of ground reaction force on the digit or by an increase in
the automatic curvature force. If there is a lack of ground
reaction force, it is plausible that the ventral and dorsal nail
matrix grow in a mismatched state resulting in an inward
curvature of the distal nail.
Pincer nails may be painful. Recurrence is high with conservative therapies (trimming, debridement, bracing) if the
underlying issues are not addressed [7]. Surgical procedures
such as the ZigZag or Inverted T may be required to correct
an associated boney osteophyte and atten out the nail bed
(Fig.1.6).
1 Nail Disorders oftheLower Extremity
Fig. 1.7 Clubbing of all digits on foot
1.2.4 Clubbing
Clubbing is an increase of both the longitudinal and transverse nail plate curvature with soft digital tissue hypertrophy. Usually, all 20 digits are involved. The condition is
caused by proliferation of the connective tissue between
the nail matrix and the distal phalanx. The angle made by
the proximal nail fold and the nail plate (Lovibond angle)
is greater than 180°, creating the “Schamroth sign,” which
is an obliteration of the normally diamond-shaped space
formed when dorsal sides of the distal phalanges of the
corresponding right and left digits are opposed [8].
Clubbing is classied into three major categories: idiopathic, hereditary, and acquired. The latter form is associated with a multitude of conditions including heart and
lung disease. Lung cancer is the most cause of clubbing.
Successful treatment of any underlying condition will
reverse clubbing.
Clubbing has been reported with Crohn’s disease, ulcerative colitis, hepatic cirrhosis, primary hypertrophic osteoar-
Fig. 1.8 Onychogryphosis of all nails
thropathy, cystic brosis, esophageal cancer, lung cancer,
bronchiectasis, lung abscess, pulmonary brosis, celiac
sprue, cyanotic congenital heart disease, bacterial endocarditis, congestive heart failure, myxoid tumor, and mesothelioma. It can also be hereditary. Treatment of the underlying
disorder may decrease or, if caught early enough, reverse the
nail pathology (Fig.1.7).
1.3 Nail Color Changes
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1.2.5 Onychogryphosis
Onychogryphosis (also known as ram’s horn nails) is gross
thickening and hardening of a nail, which becomes elongated, curved, and deformed. Onychogryphotic nails are
characterized by hypertrophic, hyperkeratotic nail plate
thickening with increased discoloration, and a loss of translucency. The terms oyster-like, claw, or ram’s horn nails have
been used to describe this deformity. The thickened nails are
often marked with transverse striations. These nails can be
painful and can lift off or ulcerate the nail bed [9].
Onychogryphosis may result from lack of proper nail
care, poor blood supply, injury to the matrix by repeated
minor trauma, onychomycosis, diabetes, and/or malnutrition. Onychogryphotic nails are also associated with pachyonychia congenita which is an autosomal dominant keratin
disorder that affects infants and children. Treatment involves
debridement of the thickened nail plate (Fig.1.8).
1.3 Nail Color Changes
1.3.1 Leukonychia
Leukonychia refers to the white discoloration of nail. It is
traditionally classied into several subtypes.
True leukonychia, where the pathology originates in the
matrix, can be total, subtotal (proximal two-thirds white and
distal part pink), or partial (transverse, punctate, or longitudinal). It may be inherited or acquired. The acquired form
may be associated with trauma, chemotherapeutic agents,
hypocalcaemia, zinc deciency, heavy metal poisoning, and
systemic diseases [10].
Mees’ lines are true leukonychia classically due to arsenic
or thallium intoxication. The condition presents as single or
multiple, transverse, narrow, non-blanching whitish lines
that run parallel to the lunula across the entire nail bed. Other
conditions associated with Mees’ lines include Hodgkin’s
disease, leprosy, tuberculosis, malaria, herpes zoster, chemotherapeutic drugs, carbon monoxide and antimony poisoning, renal and cardiac failure, pneumonia, carcinoid tumors,
childbirth and systemic lupus erythematosus [11].
Apparent leukonychia, where the pathology is in the nail
bed, is referred to as Muehrcke’s lines, half and half
(Lindsay’s) nails, and Terry’s nails. Muehrcke’s lines are
double white transverse lines caused by vascular congestion
in the nail bed. The ndings disappear with digital compression and do not migrate with the growth of the nail.
Muehrcke’s lines can result from chronic hypoalbuminemia,
liver disease, chronic renal failure, malnutrition, and cytostatic drugs. Muehrcke’s bands may be confused with Mees’
lines, the difference is that they resolve with normalization
of the serum albumin and do not grow out distally [12].
Transverse Leukonychia is also known as leukonychia
striata. Transverse leukonychia is a true leukonychia
dened by white bands in the nail plate that traverse the
width of the nail and run parallel to the lunula. These are
found on both the ngers and toes. The most common cause
of transverse leukonychia is repetitive microtrauma. The
nail disorder is also associated with ulcerative colitis, chemotherapy, acute arsenic poisoning, nutritional deciencies, and renal failure [13].
Muehrcke’s lines are double white transverse lines caused
by vascular congestion in the nail bed. They disappear with
digital compression and do not migrate with the growth of
the nail. They can result from chronic hypoalbuminemia,
liver disease, chronic renal failure, malnutrition, and cytostatic drugs. Muehrcke’s bands may be confused with Mees’
lines, the difference is that they resolve with normalization
of the serum albumin and do not grow out distally [13].
Half and half nails are also called Lindsay’s nails and
present as a discoloration of the nail with a half proximal
white portion and a distal half reddish pink to brown. The
discoloration remains xed with nail pressure and remains
stationary with nail growth, indicating that the pathology
begins within the nail bed although the underlying mechanism is not well understood. This nail condition is found in
patients with chronic renal failure.
Terry’s nails are leukonychia of the entire nail except for
a thin 1–2mm pink to brownish band at the distal free edge.
They are mainly associated with hepatic cirrhosis, but can
appear in congestive cardiac failure, diabetes mellitus,
peripheral vascular disease, chronic renal failure, leprosy,
malnutrition, tuberculosis, and HIV patients [12].
Diagnosis is made through clinical presentation and
applying digital compression. Lines that do not fade or
blanch after compression indicate nail matrix pathology.
Serial photographs of the nails can document whether the
striations grow out with the nail. Since most transverse leukonychia are caused by repetitive microtrauma, treatment is
usually not required as the lines will grow out with the nail.
When caused by a disease, toxin, or nutritional deciency
correction of the underlying etiology will improve striations
and discoloration (Fig.1.9).
1.3.2 Longitudinal Melanonychia
Longitudinal melanonychia, also known as melanonychia
striata, is a pigmented brown to black band within the nail
plate which results from deposition of melanin by nail matrix
melanocytes. Pigment extends to the distal edge of the nail
plate. Dependent on cause, longitudinal melanonychia can
involve single or multiple nails [14]. It is common in darkly
pigmented individuals with nearly all African-Americans
developing one or more bands by the age of 50. However, a
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1 Nail Disorders oftheLower Extremity
Fig. 1.9 Leukonychia of great toenail and second nail
similar solitary pigmented streak presenting in an individual
of Caucasian decent should raise suspicion of melanoma.
Extension of pigment into periungual area is referred to as
Hutchinson’s sign and may also be an important indicator of
malignancy.
Longitudinal melanonychia may result from either melanocytic activation or melanocytic proliferation. Activated
melanocytes within the nail matrix can increase melanin production without an increase in number of cells. Common
causes of longitudinal melanonychia due to melanocytic
activation include racial melanonychia, pregnancy, trauma,
inammatory states (lichen planus and psoriasis), iatrogenic
(medication), and systemic diseases (Addison’s disease).
Syndrome associated melanonychia (Laugier-Hunziker,
Peutz-Jeghers, and Touraine syndromes) also presents with
mucosal hyperpigmentation.
Melanocytic proliferation also leads to increased melanin
production. Examples are nail nevi which can be acquired or
congenital and melanoma. Extension of pigment into the
periungual area is referred to as Hutchinson’s sign.
Most cases of melanonychia are benign. Management of
underlying systemic disease or discontinuation of the offending substance may decrease nail hyperpigmentation. In the
case of suspected subungual melanoma, a biopsy should be
performed [15]. Once malignancy is established, a local
excision or amputation may be required. Subungual melanoma is commonly misdiagnosed, resulting in a treatment
delay (Fig.1.10).
Fig. 1.10 Longitudinal melanonychia as viewed with a dermatoscope
1.3.3 Green Nails/Chloronychia
An Infection of the nail plate caused by Pseudomonas aeruginosa results in a green discoloration of the nail plate.
Chloronychia is characterized by green pigmentation of the
nail plate, proximal onychocryptosis, and distal onycholysis.
The green discoloration is caused by pigments secreted by P.
aeruginosa, namely pyoverdine and pyocyanin [16]. It can
also be caused by staining from a dye in clothing or products.
The condition is usually asymptomatic. Diagnosis may be
conrmed by bacterial culture of nail scrapings.
Chloronychia may prove difcult to treat. Therapeutic
options include application of topical silver sulfadiazine,
gentamicin, polymyxin B, bacitracin, and oral quinolones
(ciprooxacin) [17]. Brushing the nail bed daily with 2%
sodium hypochlorite solution may promote clearing. No
serious sequelae have been reported (Fig.1.11) [18].
1.3.4 Yellow Nail Syndrome
Yellow nail syndrome is characterized by a triad of thickened
yellow nails, primary lymphedema, and respiratory manifestations. Yellowish to green discolored nails are the main
clinical manifestation. The discoloration represents a subset
1.4 Nail Plate–Nail Bed Adhesion Issues
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Fig. 1.11 Green nails resulting from soaking in isopropyl alcohol with
wintergreen
7
of chromonychia and xanthonychia [19]. Features may
include thickening of the nail plate with an enhanced transverse curvature, hardened/difcult-to-trim nail (scleronychia), and disappearance of the cuticle [20]. Usually
opaque and visible, the lunula “disappears” because of nail
hyperkeratosis. Onycholysis may occur with possible proximal spreading, leading to complete nail shedding [21]. The
nail changes may spontaneously improve.
1.4 Nail Plate–Nail Bed Adhesion Issues
1.4.1 Onycholysis
Onycholysis of the nail is the spontaneous separation of the
nail plate from the nail bed. Separation begins at the distal
free margin of the nail and advances proximally to the nail
matrix and lateral borders. The dethatched portion of nail
will appear yellow white in color. Onycholysis of the nail is
associated with psoriasis, candida infection, onychomycosis,
yellow nail syndrome, contact dermatitis, medications, endocrine disorders, environmental causes, connective tissue disorders, and phototoxicity. Culture is recommended to rule
out dermatophytosis. Patients should be advised to keep
nails short to avoid mechanical trauma (Fig.1.12).
1.4.2 Disappearing Nail Bed
Disappearing nail bed (DNB) is characterized by irreversible
epithelialization of the nail bed following longstanding onycholysis [22]. This phenomenon can affect both ngernails
and toenails. Factors that predispose to development of DNB
in toenails include increasing age, history of trauma, surgery,
onychomycosis, psoriasis, and onychogryphosis. DNB can
Fig. 1.12 Onycholysis of great toenail
Fig. 1.13 Disappearing nail bed of bilateral hallux nails
facilitate the growth of dermatophytes and is unsightly. It
may induce painful conditions such as distal ingrown
toenails.
Both conservative and surgical treatments have been
described for the management of DNB. The conservative
options include taping of the distal skin of the digit, wearing
shoes with a wide toe box to accommodate the deformity and
prevent further trauma, and camouaging with a cosmetic
resin. As DNB progresses, the distal pulp of the toe enlarges
and deforms. This creates a physical barrier for the nail to
grow forward and predisposes the digit to the development
of distal paronychia. One conservative method that has been
attempted is taping of the skin distal to the nail plate to
stretch the skin away from the plate and reduce the size of the
distal pulp (Fig.1.13).
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1 Nail Disorders oftheLower Extremity
1.5 Unique Toenail Issues
1.5.1 Subungual Hematoma
Subungual hematoma is a collection of blood between the
nail plate and nail bed usually caused by trauma. Bleeding
occurs in the space between the nail plate and underlying
nail bed and matrix. Since the nail is stationary, blood collects beneath the nail plate and forms a hematoma. Increase
in pressure leads to swelling and pain [23]. Extensive hematomas may suggest injury to the nail bed and matrix and even
fracture the distal phalanx. Nail trephination is the standard
treatment for relieving pressure and pain. Radiographs may
be recommended as 20–25% of subungual hematomas are
associated with phalangeal fracture [23]. Drainage may be
achieved using an 18-gauge needle, #11 scalpel, heated
paper clip, or cauterization if the hematoma involves less
than 25% of the nail plate. If greater than 25% of the nail
plate is involved, removal of the nail for direct visualization
and inspection of the nail bed is recommended. Antibiotic
therapy and tetanus prophylaxis should also be considered.
Complications of nail trephination may include temporary or
permanent nail deformity, scarring of the nail bed epithelium, infection, and inadequate evacuation (Fig.1.14).
1.5.2 Ingrown Toenails
Onychocryptosis is an ingrowing of the lateral toenail edge.
Like pincer nails, ingrown toenails contain a distal incurvated
nail edge. Contributing factors include improper nail trimming
and physical forces from ill-tting shoes. Paronychia of the
great toenail, or inammation/infection of the lateral and
proximal nail folds usually accompanies the incurvated lateral
nail plate. Purulence due to a bacterial infection is generally
seen in this condition on the feet, whereas candida infection is
more common in chronic thumb- suckers. Treatments may
entail topical antibiotic and anti-inammatory medications,
oral antibiotic therapy, taping of the offending nail border to
pull the inamed skin away from the nail, education on proper
nail trimming, incision and drainage of the abscess, and surgical removal of the onychocryptotic nail plate (partial nail avulsion or total nail avulsion) (Figs.1.15 and 1.16) [24].
1.5.3 Congenital Malalignment oftheGreat
Toenail
The hallmark of this congenital nail condition is a lateral
deviation of the nail plate with respect to the distal phalanx’s
longitudinal axis [25]. The nail is discolored presenting with
varying degrees of yellow, green, gray, black, or brown.
Greenish hue may indicate Pseudomonas colonization, and
brown or black discoloration may indicate a subungual hemorrhage or fungal infection. Wave-like transverse ridging
(Beau’s line-like) across the nail plate gives the nail an oyster
shell-like appearance. The free end of the nail may appear
pointed or triangular. The condition usually occurs bilaterally with only hallux involvement and may overlap with hallux valgus.
The nail becomes onycholytic and thickened as it progresses and is accompanied by a distal wall of skin which further prevents the nail from growing forward longitudinally.
Onychocryptosis and paronychia may develop as the nail continues its curvilinear path toward the second digit. Nails spontaneously regress in less than 50 percent of cases [25]. From a
Fig. 1.14 Subungual hematoma on hallux nail
Fig. 1.15 Onychocryptosis of lateral border of hallux nail
1.6 Dermatologic Disease Related Nail Disorders
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Fig. 1.16 Paronychia of bilateral nail borders of great toenail
9
Fig. 1.18 Retronychia of proximal nail fold
such as wearing poorly tting shoes or activities like hiking
[26]. It presents with a paronychia or granulation tissue at the
proximal nail fold and nail plate onycholysis. Females are predominately affected and the big toe is usually involved.
Treatment consists of totally avulsing the nail plate and avoidance of possible triggers to prevent future trauma (Fig.1.18).
Fig. 1.17 Congenital malalignment of great toe
surgical perspective, the optimal time to correct this deformity
is before the age of two. The traditional surgical approach is a
crescent-shaped resection proximal to the nail bed and matrix
with rotation of the entire nail unit allowing the nail plate to
grow in parallel to the distal phalanx (Fig.1.17) [25].
1.5.4 Retronychia
Retronychia describes ingrowth of the proximal nail plate into
the proximal nail fold. The condition usually follows trauma
1.6 Dermatologic Disease Related Nail
Disorders
1.6.1 Nail Psoriasis
Nail psoriasis may appear as pitting of the nail plate, leukonychia, red spots in the nail bed (salmon patches or oil
drop), onycholysis, splinter hemorrhages, and nail bed
hyperkeratosis [27]. The clinical differentiation between nail
psoriasis and other conditions such as onychomycosis is at
times challenging and both disorders may coexist. Nail psoriasis often accompanies psoriatic arthritis.
Nail psoriasis may respond to topical or intralesional corticosteroids and topical vitamin D3 analogues. Other topical
treatments include tacrolimus, uorouracil, and tazarotene.
Oral systemic therapies (acitretin, methotrexate, cyclosporine and apremilast) and biologics (including inhibitors of
tumor necrosis factor alpha, IL17 and IL23 are used to treat
moderate to severe disease (Fig.1.19) [28].
1.6.2 Nail Lichen Planus
The inammatory skin condition lichen planus (LP) involves
the nail in about 10% of patients. Fingernails are most
affected. Early disease is characterized by thinning of the
nail plate and longitudinal ridging. Pterygium results from
adhesion of the eponychium and the matrix, leading to splitting the nail. Complete loss of the nail plate may follow [29].
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