ICD-9: 681.9 ○ ICD-10: L03.019
Dermatophytes are the most common pathogens infecting the nail apparatus.
S. aureus and group A streptococcus cause acute soft-tissue infection of the nail fold.
Candida and S. aureus can cause secondary infection of chronic paronychia.
Recurrent herpes simplex virus infection.
S. aureus is the most common cause of acute paronychia.
Felon is an acute infection of the finger tip.
Management: See “Antimicrobial Therapy” in Section 25.
ICD-10 ○ L03.01
Acute infection of lateral or proximal nail fold.
Usually associated with break in integrity of epidermis (e.g., hang nail), trauma.
Findings: Throbbing pain, erythema, swelling, pain, ± abscess formation (Fig. 32-17).
Infection may extend deeper, forming a felon (Fig. 32-18).
Acute paronychia The proximal nail fold is red and edematous (cellulitis) with pus formation.
Felon An abscess is seen on the fingertip with surrounding erythema and swelling. Methicillin-sensitive S. aureus (MSSA) was isolated on culture of the pus.
ICD-9: 681.01 ○ ICD-10: L03.0
Soft-tissue infection of pulp space of distal phalanx (Fig. 32-18); closed space infection of multiple compartments created by fibrous septa passing between the skin and periosteum.
History: Penetrating injury, splint, paronychia.
Findings: Pain, erythema, swelling, abscess (Fig. 32-18).
Distribution: Thumb, index finger.
Complications: Osteitis, osteomyelitis of distal phalanx, sequestration of diaphysis of the phalanx; rupture into distal interphalangeal joint with septic arthritis; extension into distal end of flexor tendon sheath, producing tenosynovitis.
Course: May be rapid and severe; contained by unyielding skin of fingertip, infection creates tension with microvascular compromise, necrosis, and abscess formation.
Fungal Infections and Onychomycosis
Candida spp. usually cause “space” infections of chronic paronychia or onycholytic nail and can cause destruction of the nail in the immunocompromised host.
Dermatophytes infect the skin around the nail apparatus and cause superficial destruction of nail.
Onychomycosis: Chronic progressive fungal infection of nail apparatus, most commonly caused by dermatophytes, less often by Candida spp.; molds and environmental fungi can be cultured from diseased nails but are not usually primary pathogens.
Candida albicans infections of the nail apparatus occur most often on fingers, commonly as secondary infection of chronic paronychia. Onychia describes inflammation of the matrix of the nail resulting in shedding of nail.
Invasion of nail plate usually occurs only in the immunocompromised host, i.e., chronic mucocutaneous candidiasis (CMC) or HIV/AIDS disease.
Etiology and Epidemiology
C. albicans and other species. Normal flora, which causes infection if local ecology is changed in favor of yeast or in association with altered immune status. See “Candidiasis,” Section 26.
Subungual infection associated with onycholysis.
Intermittent flares of chronic paronychia.
Colonization in tinea unguium.
Total nail dystrophy (Fig. 32-19): chronic CMC and HIV/AIDS disease.
Candida onychomycosis: total dystrophic type The entire fingernail plate is thickened and dystrophic and is associated with a paronychial infection; both findings were caused by C. albicans in an individual with advanced HIV/AIDS disease.
See “Candidiasis,” Section 26.
See “Candidiasis,” Section 26.
Candidal onychia and paronychia are common in children with HIV/AIDS, often associated with mucosal candidiasis.
Chronic Paronychia with Acute Candidal Flare. Candida spp. can cause painful chronic infection with pain, tenderness, erythema, ± pus. Nail may become dystrophic with areas of opacification; white, yellow, green, or black discoloration; with transverse furrowing.
Colonization in Tinea Unguium. Secondary pathogen in distal/lateral onychomycosis.
Total Nail Dystrophy. Proximal/lateral nail folds are inflamed and thickened. Fingertips appear bulbous. Nail is invaded and may eventually become totally dystrophic (Fig. 32-19). HIV/AIDS: one nail may be involved. CMC: 20 nails may be involved in time.
See “Candidiasis,” Section 26.
Tinea unguium, psoriasis, eczema, chronic paronychia, lichen planus.
See “Candidiasis,” Section 26.
Classification by Anatomic Site Involved
Distal and Lateral Subungual Onychomycosis (DLSO)
Infection begins in hyponychial area or nail fold, extending subungually. May be either primary, i.e., involving a healthy nail apparatus, or secondary (e.g., psoriasis) associated with onycholysis. Always associated with tinea pedis.
Onychomycosis of toenails: distal and lateral subungual type (DLSO) The toenails are white, caused by onycholysis and subungual hyperkeratosis. The dorsum of the feet shows erythema and scaling, i.e., tinea pedis. T. rubrum was detected on culture.
Superficial White Onychomycosis (SWO)
Pathogen invades surface of dorsal nail (Fig. 32-21). Etiology: Trichophyton mentagrophytes or T. rubrum (children). Much less commonly, mold: Acremonium, Fusarium, Aspergillus terreus.
Onychomycosis of toenails: superficial white type (SWO) The dorsal nail plate is chalky white. White nail dystrophy can easily be treated by curettage; KOH preparation of the curetting shows hyphae.
Proximal Subungual Onychomycosis (PSO)
Pathogen enters by way of the posterior nail fold–cuticle area and then migrates along the proximal nail groove to involve the underlying matrix, proximal to the nail bed, and finally the underlying nail (Fig. 32-22). Etiology: T. rubrum. Findings: Leukonychia that extends distally from under proximal nail fold. Usually one or two nails involved. Always associated with immunocompromised states.
Tinea unguium: proximal subungual onychomycosis type The proximal nail plate is a chalky white color due to invasion from the undersurface of the nail matrix. The patient had advanced HIV/AIDS disease.
Etiology and Epidemiology
Children or adults. Once acquired, usually does not remit spontaneously. Therefore, the incidence increases with advancing age; 1% of individuals <18 years affected; almost 50% of those >70 years.
Somewhat more common in men.
Between 95% and 97% caused by T. rubrum and T. mentagrophytes.
Molds. Acremonium, Fusarium, and Aspergillus spp. can rarely cause SWO. Dermatosis such as psoriasis, which results in onycholysis and subungual hyperkeratosis, or dermatophytic onychomycosis can be secondarily colonized/infected by molds.
Worldwide. Etiologic agent varies in different geographic areas. More common in urban than in rural areas (associated with wearing occlusive footwear).
Incidence varies in different geographic regions. In the United States and Europe, up to 10% of adult population affected (related to occlusive footwear). In developing nations where open footwear is worn, uncommon.
Anthropophilic dermatophyte infections are transmitted from one individual to another, by fomite or direct contact, commonly among family members. Some spore forms (arthroconidia) remain viable and infective in the environment for up to 5 years.
Molds. Ubiquitous in environment; not transmitted between humans.
Atopics are at increased risk for T. rubrum infections. Diabetes mellitus, treatment with immunosuppressive drugs, HIV/AIDS. For toenail onychomycosis, most important factor is wearing of occlusive footwear.
Primary Onychomycosis/Tinea Unguium
The probability of nail invasion by fungi increases with defective vascular supply (i.e., with increasing age, chronic venous insufficiency, peripheral arterial disease), in posttraumatic states (lower leg fractures), or disturbance of innervation (e.g., injury to brachial plexus, trauma of spine).
Infection occurs in already altered nail apparatus, such as psoriatic or traumatized nail.
Nail bed produces soft keratin stimulated by fungal infection that accumulates under the nail plate, thereby raising it. Matrix is usually not invaded, and production of normal nail plate remains unimpaired despite fungal infection.
Approximately 80% of onychomycosis occurs on the feet, especially on the big toes; simultaneous occurrence on toe- and fingernails is not common.
White patch is noted on the distal or lateral undersurface of the nail and nail bed, usually with sharply demarcated borders. With progressive infection, the nail becomes opaque, thickened, cracked, friable, raised by underlying hyperkeratotic debris in hyponychium (Fig. 32-20). When fingernails are involved, pattern is usually two feet and one hand.
A white chalky plaque is seen on the proximal nail plate, which may become eroded with loss of the nail plate (Fig. 32-21). SWO may coexist with DLSO. Occurs almost exclusively on the toenails, rarely on the fingernails.
PSO (Fig. 32-22). A white spot appears from beneath proximal nail fold. In time, white discoloration fills lunula, eventually moving distally to involve much of undersurface of the nail. Occurs more commonly on toenails.
Psoriatic nails (“oil drop” staining of the distal nail bed and nail pits is seen in psoriasis but not onychomycosis), eczema, Reiter syndrome and keratoderma blennorrhagicum, onychogryphosis, pincer nails, congenital nail dystrophies.
Traumatic or chemical injury to nail, psoriasis with leukonychia.
All clinical diagnoses of onychomycosis should be confirmed by laboratory testing (see “Dermatophytoses,” Section 26).
For DLSO: distal portion of involved nail bed; SWO: involved nail surface; PSO: punch biopsy through nail plate to involved nail bed.
Specific identification of pathogen is usually not possible by microscopy, but, in most cases, yeasts can be differentiated from dermatophytes by morphology.
Isolation of the pathogen permits better use of oral antifungal agents.
Histology of Nail Clipping
Indicated if clinical findings suggest onychomycosis after negative KOH wet mounts. PAS stain is used to detect fungal elements in the nail. Most reliable technique for diagnosing onychomycosis.
Clinical diagnosis is never adequate. Clinical findings confirmed by finding fungal forms in KOH preparation, nail clipping, and/or isolation of pathogenic fungus on culture.
Without effective therapy, onychomycosis does not resolve spontaneously; progressive involvement of multiple toenails is the rule. DLSO persists after topical treatment of tinea pedis and often results in repeated episodes of epidermal dermatophytosis of feet, groin, and other sites. Tinea pedis and/or DLSO provide portal of entry for recurrent bacterial infections (S. aureus, group A streptococcus), especially cellulitis of lower leg after venous harvesting. Prevalence in diabetic patients estimated to be 32%; Diabetic patients need early intervention and should be screened regularly by a dermatologist and/or podiatrist. Untreated HIV/AIDS is associated with increased prevalence of dermatophytoses. Long-term relapse rate with newer oral agents such as terbinafine or itraconazole reported to be 15–21% 2 years after successful therapy; mycologic cultures may be positive without any clinically apparent disease.
TABLE 32-1MANAGEMENT OF TINEA UNGUIUM |Favorite Table|Download (.pdf) TABLE 32-1 MANAGEMENT OF TINEA UNGUIUM
|Debridement ||Debride dystrophic nails; patients should debride weekly. |
|Topical agents || |
Available as lotions and lacquer. Usually not effective except for SWO.
Ciclopirox (Penlac) nail lacquer: monthly professional nail debridement recommended.
|Systemic agents ||Note: In systemic treatment of onychomycosis, nails usually do not appear normal after the treatment times recommended because of slow growth of nail. If cultures and KOH preparations are negative after these time periods, medication can nonetheless be stopped and nails will usually regrow normally. |
|Terbinafine (Allylamine) ||250 mg/d for 6 weeks for fingernails and 12–16 weeks for toenails; most effective against dermatophyte infections. |
|Itraconazole: approved (USA) for onychomycosis. Effective in dermatophytes and Candida only ||200 mg/d for 6 weeks (fingernails), 12 weeks (toenails) (continuous therapy). Although not approved for toenail onychomycosis, pulse dosing is used, given for 3–4 months at 200 mg twice daily for first 7 days of every month (continue treatment for 12 weeks for toenail involvement). |
|Fluconazole: not approved (USA) for onychomycosis. Effective in dermatophytes and Candida ||Reported effective at dosing of 150–400 mg 1 day per week or 100–200 mg/d until the nails grow back normally. Effective in yeasts and less so in dermatophytes. |
|Ketoconazole: not approved for onychomycosis. ||Effective at 200 mg/d; more effective for Candida than dermatophytes; however, infrequently hepatotoxicity and antiandrogen effect have limited its long-term use for onychomycosis. |
|Secondary prophylaxis || |
Antifungal cream, lotion, or powder daily.
Antiseptic gels: ethanol or isopropyl alcohol.
Pedicures/manicures: make sure instruments are sterilized or individuals have their own.
Indications for Systemic Therapy
Fingernail involvement, limitation of function, pain (thickened great toenails with pressure on nail bed, ingrowing toe nails), physical disability, potential for secondary bacterial infection, source of recurrent epidermal dermatophytosis, quality-of-life issues (poorer perceptions of general and mental health, social functioning, physical appearance, difficulty in trimming nails, discomfort in wearing shoes). Early onychomycosis is easier to cure in younger, healthier individuals than in older individuals with more extensive involvement and associated medical conditions.