Paronychia is an infection of the proximal and lateral fingernails and toenails folds, including the tissue that borders the root and sides of the nail. This condition can occur spontaneously or following trauma or manipulation. Paronychia is among the most common infections of the hand. Paronychia results from the disruption of the protective barrier between the nail and the nail fold, introducing bacteria and predisposing the area to infection. Acute paronychia is usually limited to one nail; however, if drug-induced, it can involve many nails.[rx][rx]
Types of Paronychia
The classification of paronychia is according to the clinical presentation:
Acute paronychia – lasting less than six weeks, painful and purulent condition; most frequently caused by a bacterial infection, especially staphylococci.
Chronic paronychia – usually caused by mechanical or chemical factors and sometimes infectious etiology like a fungal infection, especially Candida species. Risk factors include occupation (dishwasher, bartender, housekeeper), certain medications, and immunosuppression (diabetes, HIV, malignancy).
- Prosector’s paronychia – is a primary inoculation of tuberculosis of the skin and nails, named after its association with prosectors, who prepare specimens for dissection. Paronychia around the entire nail is sometimes referred to as runaround paronychia.
- Painful paronychia – in association with a scaly, erythematous, keratotic rash (papules and plaques) of the ears, nose, fingers, and toes may be indicative of acrokeratosis paraneoplastic, which is associated with squamous cell carcinoma of the larynx.
Classification can also be by etiology
Bacterial, commonly staphylococci
Viral, commonly Herpes simplex virus
Fungal, commonly Candida species
Noninfectious causes of paronychia can include contact irritants, excessive moisture, and medication reaction.[rx]
According to diagnostic Criteria of paronychia are
- Cellulitis – Cellulitis is a superficial infection and will present as erythema and swelling to the affected portion of the body with no area of fluctuance. Treatment is with oral antibiotics.
- Felon – A felon is a subcutaneous injection of the digital pulp space. The area becomes warm, red, tense, and very painful due to the confinement of the infection, creating pressure in the individual compartments created by the septa of the finger pad. These require excision and drainage, usually with a longitudinal incision and blunt dissection to ensure adequate drainage.
- Herpetic whitlow – This is a viral infection of the distal finger caused by HSV. Patients usually develop a burning, pruritic sensation before the infection erupts. A physical exam will show vesicles, vesicopustules, along with pain and erythema. It is important to not confuse this with a felon or a paronychia as incision and drainage of herpetic whitlow could result in a secondary bacterial infection and failure to heal.
- Onychomycosis – This is a fungal infection of the nail that causes whitish-yellowish discoloration. Sometimes difficult to treat and requires oral antibiotics instead of topical.
- Nail Psoriasis – psoriasis can also affect the fingernails and toenails. It may cause thickening of the nails with areas of pitting, ridges, irregular contour, and even raising of the nail from the nail bed.
- Squamous cell carcinoma – Squamous cell carcinoma is mainly cancer of the skin but can also affect the nail bed. It is a rare malignant subungual tumor subject to misdiagnosis as chronic paronychia.[rx][rx]
Causes of Paronychia
- Infections (Bacterial, mycobacterial, or viral)
- Raynaud’s disease
- Metastatic cancer, subungual melanoma, squamous cell carcinoma. Benign and malignant neoplasms should always be excluded when chronic paronychia does not respond to conventional treatment
- Papulosquamous disorders like psoriasis, vesiculobullous disorders-pemphigus
- Drug toxicity from medications such as retinoids, epidermal growth factor receptor inhibitors (cetuximab), and protease inhibitors. Indinavir- induces retinoid-like effects and remains the most frequent cause of chronic paronychia in patients with HIV disease.
- Retinoids also induce chronic paronychia. The mechanism can be -nail fragility and minor trauma by small nail fragments.[rx] Paronychia has also been reported in patients taking cetuximab (Erbitux), an anti-epidermal growth factor receptor (EGFR) antibody used in the treatment of solid tumors.[rx]
- Acute paronychia is usually caused by bacteria. Paronychia is often treated with antibiotics, either topical or oral or both. Chronic paronychia is most often caused by a yeast infection of the soft tissues around the nail but can also be traced to a bacterial infection. If the infection is continuous, the cause is often fungal and needs antifungal cream or paint to be treated.[rx]
- Repeatedly washing hands and trauma to the cuticle such as may occur from repeated nail-biting. In the context of bartending, it is known as bar rot.[rx]
Paronychia can occur with diabetes, drug-induced immunosuppression,[rx] or systemic diseases such as pemphigus.[rx]
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