Diseases of The Nail Part 2

Longitudinal pigmented bands

Longitudinal pigmented bands (melanonychia striata), also referred to as longitudinal melanonychia, is the presence of single or multiple longitudinally oriented brown or black bands [see Figure 4]. Homogeneous longitudinal bands occur in approximately 75% of African Americans older than 20 years. It usually affects the thumb and index finger.30,31 Melanonychia striata is also commonly seen in Hispanics, may be found in up to 20% of Japanese, and is rare in whites.30

The deposition of melanin in the nail plate may result from increased melanin synthesis by matrix melanocytes that are usually nonfunctional; it may also occur as a result of a prolif-eration of matrix melanocytes.

 Melanonychia striata (longitudinal pigmented band) produced by a melanocytic nevus of the nail matrix. A high index of suspicion for subungual melanoma is very important when a longitudinal pigmented band of the nail is identified.


Figure 4 Melanonychia striata (longitudinal pigmented band) produced by a melanocytic nevus of the nail matrix. A high index of suspicion for subungual melanoma is very important when a longitudinal pigmented band of the nail is identified.

Melanonychia striata affecting a single nail may result from a benign melanocytic nevus or a subungual melanoma. Thus, it is important to distinguish between a benign cause and a malignant cause of a longitudinal pigmented band. Factors suggesting the presence of melanoma or an atypical melanocytic proliferation are (1) single digit involvement; (2) periungual spread of pigment onto the nail-fold region (Hutchinson sign); (3) border irregularity or variegated color within the linear streak; and (4) changes in appearance (e.g., color or borders) involving an established longitudinal band.32 Because of the severity of subungual melanoma and the importance of making a prompt diagnosis, the index of suspicion must be high. A simple biopsy of the nail plate is not satisfactory in establishing the diagnosis, because it will only demonstrate the presence of melanin. An appropriate biopsy inclusive of the nail matrix, as well as the nail bed if clinically indicated, should be performed by a surgeon who is familiar with the intricacies of performing a nail biopsy.33 Because of limited experience and the difficulties that are commonly con-fronted in the histologic interpretation of nail specimens, biopsies of melanonychia striata are best interpreted by a dermatopathologist.

Psoriasis of the nail, characterized by subungual hyperkeratosis and loss of distal onycholytic nail plate. This patient was unsuccessfully treated with oral antifungal therapy after an erroneous diagnosis of onychomycosis was made on the basis of clinical diagnosis alone. Careful examination of the proximal intact nail plate reveals pitting, a feature characteristic for psoriasis and not onychomycosis.

Figure 5 Psoriasis of the nail, characterized by subungual hyperkeratosis and loss of distal onycholytic nail plate. This patient was unsuccessfully treated with oral antifungal therapy after an erroneous diagnosis of onychomycosis was made on the basis of clinical diagnosis alone. Careful examination of the proximal intact nail plate reveals pitting, a feature characteristic for psoriasis and not onychomycosis.

(a) When obtaining a nail specimen for potassium hydroxide (KOH) preparation, it is important to expose the affected nail bed by first trimming away and discarding the distal, separated (onycholytic) nail plate. (b) Small specimen fragments of subungual hyperkeratosis of the nail bed and exposed undersurface of the nail plate are effectively obtained using a small curette. The smaller fragments are more easily dissolved by KOH, allowing for more accurate microscopic visualization, and can be easily plated on fungal culture medium.

Figure 6 (a) When obtaining a nail specimen for potassium hydroxide (KOH) preparation, it is important to expose the affected nail bed by first trimming away and discarding the distal, separated (onycholytic) nail plate. (b) Small specimen fragments of subungual hyperkeratosis of the nail bed and exposed undersurface of the nail plate are effectively obtained using a small curette. The smaller fragments are more easily dissolved by KOH, allowing for more accurate microscopic visualization, and can be easily plated on fungal culture medium.

When nail-bed pigmentation is noted, other causes such as systemic drugs (e.g., antimalarials, zidovudine, bleomycin, doxorubicin, minocycline, and hydroxyuria) or systemic disease (e.g., Addison disease and HIV infection) must be considered; however, these causes usually result in a broader, more diffuse pigmentation, often involving multiple nails.35 Another reported association with melanonychia striata is systemic lupus erythematosus.36 Frictional melanonychia resulting from trauma from athletic activities or poorly fitting shoewear may cause nail pigmentation, including pigmentation of the nail fold, especially in dark-skinned persons (pseudo-Hutchinson sign).32

Bacterial and Fungal Nail Infections

Bacterial paronychia

Bacterial infection of the nail folds (bacterial paronychia) is usually acute in nature. It is is characterized by swelling, erythema, discomfort, and sometimes purulence. The most common etiologic pathogen is Staphylococcus aureus. Treatment requires drainage of a focal abscess, if present, and oral antibiotic therapy.37

Chronic paronychia

Chronic paronychia results from persistent or frequently recurrent nail-fold inflammation, which is usually the result of chronic irritant dermatitis and loss of cuticle from trauma or nail-care practices. Secondary candidal infection may occur.

Table 1 Oral Antifungal for Toenail Onychomycosis*46

Drug

Dosage

Comments

Griseofulvin tablets or liquid

500 mg – 1 g daily x 12 – 18 mo

Generally not recommended because of limited efficacy and because more effective agents are available; only active against dermatophyte organisms

Itraconazole capsules

Pulse therapy+: 200 mg twice daily x 1 wk/mo for 3 consecutive mo

Contraindications include specific drug interactions and congestive heart failure; potential hepa-totoxicity (rare); effective for dermatophytes, Candida species, and some nondermatophytic molds; should be administered with food; absorption may be decreased by increased gastric pH (as might result from use of H2 blockers, antacids, proton pump inhibitors); blood clearance in 1 – 2 wk; therapeutic nail levels 9 mo posttherapy

Continuous therapy: 200 mg daily x 3 mo

Terbinafine tablets

250 mg daily x 3 mo

Most active for dermatophytes; some efficacy for certain nondermatophytic molds; limited activity against most Candida species; potential hepatotoxicity (rare); sporadic reports of blood dyscrasias (rare); reversible change or loss of taste (< 2%); blood clearance in 1 – 2 mo; therapeutic nail levels 9 mo posttherapy

Fluconazole tablets*

150 – 300 mg x 9 – 12 mo

Effective against dermatophytes and Candida species; potential hepatotoxicity (rare); some significant drug interactions; limited therapeutic drug reservoir in nail posttherapy

*Topical ciclopirox 8% nail lacquer is FDA approved for onychomycosis caused by Trichophyton rubrum. Treatment involves application once daily for 12 mo (or until outgrowth of clear nail occurs), combined with debridement/trimming of onycholytic nail plate. Efficacy is lower than that seen with newer oral agents (e.g., itraconazole, terbinafine). No oral or topical agent is currently FDA approved for nondermatophytic onychomycosis (e.g., Candida species, molds). +Pulse itraconazole is FDA approved for fingernail tinea unguium; established efficacy has been demonstrated for toenail disease. tFluconazole is not FDA approved for onychomycosis; established efficacy has been demonstrated for tinea unguium.

Table 2 Selected Dermatologic Disorders Affecting the Nail Unit

Disease State

Disease Features

Nail Findings

Inflammatory diseases Psoriasis

Nail findings in 10% – 50% of patients; 39% of children with psoriasis with nail changes (usually pitting); nail disease present in 50% – 85% of patients with psoriatic arthritis

Proximal matrix involvement: pitting, transverse grooving, deeply ridged plate surface (onychorrhexis)

Distal matrix involvement: plate thinning, lunula erythema Nail bed: subungual hyperkeratosis, oil drop sign, splinter hemorrhages

Nail folds: cutaneous lesions of psoriasis

Phalangeal/joint involvement: psoriatic arthritis

Lichen planus

Nail changes occur in up to 10% of patients with lichen planus; may occur in childhood or adulthood; nail involvement may be present with or without skin or mucos-al disease; potentially reversible in early inflammatory stage; irreversible in cicatricial (later stage) of disease; may present as ridged, rough-surfaced, lusterless plates (tra-chyonychia) or 20-nail dystrophy in children

Matrix involvement: combination of nail-plate ridging, splitting, and progressive uniform thinning; distal-edge splitting, fragility, crumbling, brittleness, nail-plate shedding (onychomadesis)

Focal matrix scarring: pterygium formation (scarring bridge between proximal nail fold and subungual epidermis with focal loss of nail plate)

Nail-bed involvement: subungual hyperkeratosis, onycholysis

Diffuse matrix/nail-bed disease: total nail-plate loss, atrophy, scarring

Alopecia areata

Nail changes in 10% of patints with alopecia areata; nail changes in over 40% of children with alopecia areata; fingernail involvement most common; may present in children as 20-nail dystrophy

Matrix involvement: orderly nail pitting arranged in a cross-hatched pattern (glen-plaid sign); roughened nail-plate surface (trachyonychia); fragility; splitting; longitudinal ridging; spotted or red lunula (erythema); nail-plate shedding (onychomadesis)

Nail tumors Glomus tumor

75% occur on the hand, usually subungual (nail bed); a benign vascular hamartoma

Visible through plate as a light-red, reddish-blue spot; rarely exceeds 1 cm in size; characteristic symptom of intense or pulsatile pain; pain is spontaneous or provoked by slight trauma or pressure

Digital myxoid

(mucus) cyst

A form of focal mucinosis; not a true cyst (no epithelial lining); contains clear, viscous, jellylike fluid; usually seen in adults

Soft, domed, translucent, pink or skin-colored, shiny, soft neoplasm of proximal nail fold or overlying distal inter-phalangeal joint; those over fold may compress matrix, producing flattening of plate; those over joint may connect to underlying joint space

Subungual exostoses

Outgrowths of calcified cartilage or normal bone; most seen on great toe; most frequent in adolescents and young adults; benign lesions

Emerge from the dorsal digit at distal phalanx; may erode through plate or project from under distal or lateral edge of plate; often painful; may become eroded

Periungual angiofibromas

Arise out of nail fold; often multiple; seen in 50% of cases of tuberous sclerosis (Borneville-Pringle disease); usually arise in early teenage years; benign neoplasm

Small, round, flesh-colored or pink, firm papules with shiny, smooth surface arising from nail-fold region; may partially cover nail plate; usually asymptomatic

Onychomycosis

Onychomycosis, the most common infection of the nail, is a fungal infection characterized by nail-bed and plate involvement. Dermatophyte onychomycosis (tinea unguium) is the most common type of fungal nail infection.39 It is seen far more commonly in adults than in children and most frequently affects one or more toenails. The mode of fungal invasion usually presents as distal-lateral subungual onychomycosis, occurring as dermatophyte organisms migrate from pedal skin to below the nail plate and invade nail-bed tissue.40 Tinea pedis and ony-chomycosis frequently coexist in a patient.41,42

The dermatophytes that most commonly cause onychomyco-sis are Trichophyton rubrum and T. mentagrophytes.43 The tendency to harbor dermatophytes (especially T. rubrum), predominantly on pedal skin, has been noted in some kindreds. As a result, patients with such a tendency are prone to tinea pedis, tinea unguium, tinea cruris, and diffuse tinea corporis. They may present with dermatophyte infections earlier in life than usually seen and often experience recurrence of dermatophyte infection after completion of initially effective therapy.

The most characteristic clinical features of dermatophyte onychomycosis are distal onycholysis, subungual hyperkerato-sis, and a dystrophic, discolored nail plate.42 Because this combination of features is also seen in persons with nail psoriasis, accurate diagnosis may require performance of a potassium hydroxide (KOH) preparation and fungal culture [see Figure 5]. It is important that specimens be obtained from the nail bed [see Figure 6] and that culture specimens be transported and plated appropriately, because different culture media are required for identification of dermatophyte and nondermato-phyte fungal nail pathogens.42 Dermatophyte test medium (DTM) may be used as an in-office culture technique that has no special incubation requirements. DTM is inexpensive and accurate in the diagnosis of dermatophyte onychomycosis.44 The clinical presentation of proximal white subungual ony-chomycosis, another presentation of dermatophyte onychomy-cosis, has been reported in association with systemic immuno-suppression, including HIV disease.45

Candida onychomycosis is far less common than dermato-phyte onychomycosis. Candida onychomycosis is often associated with immunosuppression (e.g., HIV disease and chronic mucocutaneous candidiasis). The Candida organisms may invade the nail as a secondary pathogen, and they more frequently affect the fingernails.42 Nondermatophyte molds, including Aspergillus species, Scopulariopsis brevicaulis, Fusarium species, Scy-talidium hyalinum, and Scytalidium dimidiatum, have been reported to cause fingernail or toenail infection; however, such infections are relatively uncommon.42,46 Associated paronychia may be seen when nondermatophytic fungi cause onychomy-cosis. Effective therapy for onychomycosis includes the use of an oral antifungal agent [see Table 1].47 Because nails grow slowly, clinical response is delayed.46 Infections with Scytalidium species are rare in the United States, and such infections respond poorly to currently available antifungal agents.

Dermatologic disorders affecting the nail

Complete reviews of dermatologic, systemic, neoplastic, and exogenous disorders affecting the nail are beyond the scope of this subsection. An overview of selected dermatologic disorders affecting the nail unit and their associated clinical findings is provided [see Table 2].

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