Infections of the nail apparatus

 

• 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.

 

Nail fold infections

 

Paronychia is a soft tissue infection around a fingernail that begins as cellulitis but that may progress to a definite abscess. The two types of paronychia are as follows: 

·        Acute paronychia - Painful and purulent condition; most frequently caused by staphylococci

·        Chronic paronychia - Usually caused by a fungal infection

 

Pathogenesis of paronychia

 

Paronychia, whether acute or chronic, results from a breakdown of the protective barrier between the nail and the nail fold. The occurrence of cracks, fissures, or trauma allowing organisms to enter the moist nail crevice leads to bacterial or fungal (yeast) colonization of the area.  Early in the course of this disease process (< 24 h), cellulitis alone may be present. An abscess can form if the infection does not resolve quickly.

 

Acute paronychia

 

Acute paronychia is due to acute Infection of lateral or proximal nail fold, usually results from a traumatic event, however minor, that breaks down the physical barrier between the nail bed and the nail; this disruption allows the infiltration of infectious organisms.

Acute paronychia is a common complaint usually due to staphylococcal infection, but recurrent episodes of acute paronychia should raise the suspicion of an HSV infection. Cytology (Tzanck smear) may be useful in distinguishing viral from bacterial paronychia. Bacterial paronychia  may result from local injuries, a prick from a thorn in a lateral nail groove, a splinter, torn hangnails or nail biting, the two latter being the most common predisposing factors. It also occurs frequently as an episode during the course of chronic paronychia, when other organisms may be involved including staphylococci, streptococci, Pseudomonas aeruginosa, coliform organisms and Proteus vulgaris.

 

Clinical features

 

Most patients are children and adolescents.

The patient is usually otherwise healthy but complains of pain, tenderness, and swelling in one of the lateral folds of the nail.

Physical findings in acute paronychia include the following:

·        The affected area often appears erythematous and swollen

·        In more advanced cases, pus may collect under the skin of the lateral fold and compression of the nail fold may produce purulent drainage

·        Further extension of the infection can lead to the involvement of both lateral folds as it tracks under the nail sulcus; this progression is called a run around infection

·        Infection may extend deeper, forming a felon

 

Complications of acute paronychia may include osteitis and amputation.  Acquired periungual fibrokeratoma after staphylococcal paronychia has been reported.

As trauma and terminal phalanx fractures can mimic acute paronychia, radiography is advised when the latter occurs after trauma.

FELON

 

• Soft-tissue infection of pulp space of distal phalanx; closed space infection of multiple compartments created by fibrous septa passing between the skin and periosteum.

• History: Penetrating Injury, splint, and acute paronychia.

• Findings: Pain, erythema, swelling, and abscess.

• Distribution: Thumb and index finger.

• Complications: Osteitis, osteomyelitis of distal phalanx, septic arthritis; extension into distal end of flexor tendon sheath, and producing tenosynovitis.

• Course: May be rapid and severe.

 

 

Herpetic paronychia

 

It is a viral infection of the pulp of the fingertip and the perionychium that can often be confused with the more common acute bacterial paronychia. Herpes simplex virus 1 causes approximately 60% of cases of herpetic whitlow, and herpes simplex virus 2 causes the remaining 40% of cases.

 

This uncommon condition appears mostly in children under 2 years old. It is due to primary inoculation of the herpes simplex virus from herpes stomatitis or herpes labialis and presents as single or grouped blisters on an erythematous base close to the nail; it may give a honeycomb appearance. Clear at first, the blisters soon become purulent and may rupture and be replaced by crusts. The infection is usually very painful and takes about 3 weeks to resolve, with pain for half that time. Lymphangitis sometimes occurs and may precede vesiculation. Diagnosis may be established by recovering the virus from a recent blister and by cytological examination of the blister floor (Tzanck smear). Transmission to contacts may occur, explaining the appearance of herpetic whitlow in dental workers or nurses who do not wear gloves and come into contact with herpes labialis.

 

Treatment probably does little to shorten the course of the disorder, but cleaning with chlorhexidine followed by application of a bland cream is recommended. Relapse may occur as with other primary herpetic infections. Long‐term treatment with thymidine analogues, such as oral aciclovir, famciclovir and valaciclovir, may be useful if recurrences are frequent.

Numbness of the finger has been reported following infection, as well as persistent lymph edema. Herpetic paronychia may cause complete destruction of the nail, bacterial super infection and systemic spread that may cause meningitis. Longstanding cases, particularly in patients with HIV infection, may have an atypical, often verrucous appearance.

 

Chronic paronychia

Chronic paronychia is an inflammatory dermatosis of the nail folds which causes retraction of the periungual tissues with resultant secondary effects on the nail matrix, nail growth and soft‐tissue attachments.

 

Etiology and pathogenesis

Chronic paronychia is a multifactorial inflammatory condition of the nail folds. Irritant, allergic and protein contact dermatitis are the suggested major pathogenic mechanisms. Hypersensitivity to Candida is more likely to be the etiology, rather than the infection itself. Although previously thought to be candidal in origin, chronic paronychia is now regarded as dermatitis of the nail fold often associated with prolonged wet work.  

Although the pathogenesis is still debated, there is accumulating evidence that the condition represents a contact reaction to irritants or allergens. Mechanical or chemical traumas damage the cuticle and permit penetration of irritant and allergenic environmental substances sequestered beneath the proximal nail fold, causing an inflammatory reaction of the nail folds and matrix.

Prolonged wet work with retention of moisture leading to skin barrier breakdown or chronic contact dermatitis being the primary insult.  Disruption of the cuticle results in breakdown of the protective seal between the nail fold and nail plate. Thus a space is created by separation of the proximal dorsal nail plate and the undersurface of the proximal nail fold. This provides a portal of entry for environmental irritants, allergens and microbes, triggering an inflammatory process. 

Infection mainly plays a role in perpetuating the inflammation rather than being the primary pathogenic cause. Candida has been the most common organism in patients of chronic paronychia.  It is regarded as a secondary colonizer as it disappears once the physiological barrier in the nail is restored. 

Common allergens are nickel and paraphenylene diamine. Role of candida is evidenced by positive fungal culture with Candida albicans and positive prick test with Candida allergen. 

Acute exacerbations occur from time to time and are due to secondary bacterial infection. Various organisms may be found, including Staphylococcus aureus or Staph. epidermidis, Proteus vulgaris, Escherichia coli and Pseudomonas aeruginosa.

 

Chronic paronychia most often occurs in persons whose hands are repeatedly exposed to moist environments or in those who have prolonged and repeated contact with caustic irritants such as mild acids, mild alkalis, or other chemicals. Occupational chronic paronychia is common in food handlers. Cold wet hands are predisposed to chronic paronychia. Handling of wet foods represents a particular hazard, as these often combine several predisposing factors including wet working conditions, a cold environment and irritation from the food itself. Chronic paronychia is predominantly a disease of domestic and catering workers, bartenders, florists, bakers, and swimmers and fishmongers.

Other conditions associated with abnormalities of the nail fold that predispose individuals to chronic paronychia include psoriasis or atopic eczema, where minor provocation can result in active disease.

 

Chronic paronychia is a disease predominantly affecting women, particularly housewives associated with prolonged wet work and repeated trauma to the cuticle. Wet work with detergents is well known to produce irritant effects as they contain mild acids and alkalis. Frequent washing of hands is the most common risk factor. Housewives frequently wash dishes with bare hands with resultant overexposure to common irritants and allergens. Chronic paronychia often occurs in diabetics and immunosuppressed patients. 

 

Immediate hypersensitivity to Candida is a more common factor leading to paronychia than Candida infection. Hypersensitivity to Candida could be a possible cause for persistent inflammation of the nail folds. Chronic inflammation causes fibrosis of the nail folds which presents commonly as a persistent swelling, less frequently associated with pain. Fibrosed nail folds in chronic paronychia exert pressure on the growing nail plate resulting in transverse ridges. The inflammation of the germinal matrix could, in turn, also lead to nail plate changes which serve as markers of chronicity. Transverse ridges and nail plate discoloration followed by scaling, longitudinal ridging and dystrophy are the common findings.

Thus, prolonged wet work leads to loss of the protective cuticle of the nail and separation of nail fold from nail plate, forming a pocket-like structure which serves as a repository for secondary Candidal invasion. The presence of Candida leads to hypersensitivity which further accentuates the inflammatory process and is responsible for maintenance of the disease. Hence, while choosing treatment options for chronic paronychia, in addition to eradicating the fungus with antifungals, it is also necessary to treat the hypersensitivity with topical steroids or tacrolimus.  

Clinical features

 

Generally, patients report symptoms lasting 6 weeks or longer. Inflammation, pain, and swelling may occur episodically, often after an exposure to water or a moist environment.

 

Chronic paronychia is an inflammatory disorder that almost exclusively involves the fingernails of adult women. Any finger may be involved, although it is most frequently the thumb, index and middle fingers of the (dominant) right hand and the middle finger of the left. These fingers may be more subject to minor trauma than the others. Clinically, the condition begins as mild erythema and swelling of the proximal and lateral nail folds without fluctuance. It may be painless but, if tender, is much less so than in acute paronychia. The cuticle is lost and pus may form below the nail fold. Inflammation adjacent to the nail matrix disturbs nail growth. As a result the nail plate may show superficial abnormalities such as transverse depressions (Beau’s lines) with thickening and yellowish discoloration.

 

There is some evidence that the darkening of the lateral edges of the nail plate may be due to the pigment of Candida spp. though it is sometimes associated with Pseudomonas infection of the nail. Green coloration of the nail may suggest Pseudomonas species infection. Candida paronychia can be observed in children who have oral candidosis and a habit of finger or thumb sucking. Neoscytalidium dimidiatum may also produce darkening of the lateral edges of the nail plate; by contrast, paronychia due to moulds such as Fusarium spp. is often associated with proximal leukonychia.

 

In longstanding cases, the size of the nail may be reduced, and this reduction is exaggerated by the bolstering of the fold all around the nail.

 

Grade wise severity of chronic paronychia by Tosti et al

 

 

 

Diagnostic considerations

 

The diagnosis of paronychia is based primarily on patient history and physical examination. Some laboratory studies, however, can be useful.

 

Fluctuant paronychia usually results from bacterial infection; therefore, routine Gram staining and culture can help in identifying the causative organism.

 

Potassium hydroxide (KOH) 5% smears may be helpful in diagnosing paronychia if Gram staining results are negative or if candidal infection is suspected, as in chronic paronychia. If Gram staining results are negative, the KOH preparation may demonstrate pseudomycelia and clusters of grapelike yeast cells.

 

Tzanck smears may be performed if herpetic whitlow is suspected. Smears should be performed by using base scrapings of an unroofed vesicle. The presence of multinucleated giant cells, often with visible viral inclusions, indicates a positive result.

 

Imaging studies

Although imaging studies are not routinely necessary with paronychia, obtain a plain film radiograph of the fingertip if osteomyelitis is suspected.

 

A radiograph can also be obtained if the patient has a history of recent finger trauma.

 

Prognosis

 

If treated promptly, paronychia usually has a good prognosis, but it potentially can result in a more serious infection, such as septic tenosynovitis, osteomyelitis, or, by spreading to the pulp space of the finger, a felon. Such infections develop more readily in patients who are immunosuppressed or in those whose condition has been mistreated or neglected. Secondary ridging, thickening, and discoloration of the nail can also occur, as may nail loss.

 

 

Management

 

Herpetic whitlow and paronychia must be distinguished because the treatments are drastically different. Misdiagnosis and mistreatment may do more harm than good. Once herpetic whitlow is ruled out, one must determine whether the paronychia is acute or chronic and then treat it accordingly. 

 

Acute paronychia

 

The treatment of choice depends on the extent of the infection. If diagnosed early, acute paronychia without obvious abscess can be treated non-surgically. If soft tissue swelling is present without fluctuance, then warm water soaks of the affected finger 3-4 times per day until symptoms resolve are helpful.

 

Patients with extensive surrounding cellulitis or with a history of diabetes, peripheral vascular disease, or an immunocompromised state may benefit from a short course of antibiotics. Oral antibiotics with gram-positive coverage against S aureus, such as amoxicillin and clavulanic acid (Augmentin), clindamycin, or cephalexin, are usually administered concomitantly with warm water soaks. (Although antibiotics are commonly prescribed, most patients do not require antibiotics for a simple paronychia.) Clindamycin and Augmentin also have anaerobic activity; therefore, they are useful in treating patients with paronychia due to oral anaerobes contracted through nail biting or finger sucking. Clindamycin should be used instead of Augmentin in patients who are allergic to penicillin.

 

If the paronychia does not resolve or if it progresses to an abscess, it should be drained promptly.

 

If the abscess is superficial it may point close to the nail and can easily be drained by incision with a pointed (no. 11) scalpel without anesthesia.

In deeper paronychial abscess, especially if the pus collection is located under the proximal nail fold, surgical intervention under local anesthesia is required. The abscess can be drained simply by gently elevating the eponychial fold from the nail by using a small blunt instrument such as a metal probe or an elevator. This separation is performed at the junction of the perionychium and the eponychium and extends proximally enough to permit visualization of the proximal nail plate edge. Then, the proximal third of the nail plate is removed by cutting transversally with nail‐splitting scissors and the pus evacuated. This gives more rapid relief and more sustained drainage.

The wound should be well irrigated with isotonic sodium chloride solution, and plain gauze packing should be inserted under the fold to keep the cavity open and allow drainage. The patient should receive oral antibiotics for 7 days. The packing is removed after 2 days, and warm sodium chloride solution soaks are begun. Soaking the finger twice a day in an antiseptic solution such as chlorhexidine results in rapid healing.

 

 

Chronic paronychia

 

Treatment is a combination of avoidance of precipitants, hand care and medication. Any manipulation of the nail, such as manicuring of the proximal nail fold, finger sucking, or attempting to incise and drain the lesion, should be avoided; these manipulations may lead to secondary bacterial infections. Hand protection from the environmental hazards is mandatory for remission of chronic paronychia, which can be considered cured only when the cuticle has regrowth.

 

Perhaps the most important part of the treatment, but the one most difficult to achieve, is keeping the hands dry. Patients involved in wet work should be advised to wear cotton gloves under rubber or plastic gloves. General hand care with emollients and protection from trauma and irritants is helpful. If these precautions are not followed, the condition is unlikely to settle whatever medical treatment is given.

Chronic paronychia should be treated as contact dermatitis and requires a combination with topical steroids or tacrolimus and antimicrobial to prevent secondary microbial colonization. A potent steroid may be used for short periods if there is adequate antimicrobial cover. Injected triamcinolone (2.5 mg/mL) is very useful. Topical imidazoles are usually sufficient to treat Candida and may provide modest activity against some bacteria. Oral fluconazole may be added in more severe cases. Twice a day application of Dakin solution (sodium hypochlorite) is very effective against Pseudomonas infection.

When significant nail dystrophy ensues and medical therapy has been unsuccessful, chronic paronychia can be treated surgically with good results and resolution of the dystrophic nail. In patients who experience repeated acute flares associated with chronic paronychia, additional removal of the base of the nail plate is useful.

 

Prevention

 

Patients should also avoid any further trauma to or manipulation of the nail. Hangnails should be trimmed to a semilunar smooth edge with a clean, sharp nail plate trimmer. Patients should not bite the nail plate or lateral nail folds.

 

Patients should also avoid prolonged hand exposure to moisture. (Rubber or latex-free gloves can be worn.) If hand washing must be frequent, patients should use antibacterial soap, thoroughly dry their hands with a clean towel, and apply an antibacterial moisturizer.