This article includes the etiology and pathophysiological data of each entity, classifying them as dermatologic, systemic, infectious, neoplastic, traumatic, and other classifications. The entities inherent to the periungual folds are also included, such as acute paronychia, chronic paronychia, retronychia, hangnails, hematomas of the proximal fold caused by oximeter, onychocryptosis, hypertrophy of the lateral folds, and infections caused by Candida albicans , Pseudomonas, and Staphylococcus aureus . Additionally, pathologies caused by diabetes mellitus, sepsis, endocarditis, drug reactions, and finally less frequent diseases that also affect the nail folds are discussed.
Key points
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The periungual folds, both proximal and lateral, are part of the nail apparatus and can present their own pathologies as well as those associated with multiple causes related to dermatologic, systemic, or infectious diseases, as well as drug reactions, tumors, trauma, and other causes.
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There are many entities inherent to the periungual folds, such as acute paronychia, chronic paronychia, retronychia, hangnails, hematomas of the proximal fold due to oximeter, onychocryptosis, hypertrophy of the lateral folds, and infections caused by Candida albicans, Pseudomonas, and Staphylococcus aureus .
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The pathology of the periungual folds can provide a wealth of data about local or systemic diseases, and the diverse manifestations can lead physicians to improve diagnosis and offer better treatments.
Introduction
The periungual folds, both proximal and lateral, are part of the nail apparatus and can present their own pathologies as well as those associated with multiple causes related to dermatologic, systemic or infectious diseases, as well as drug reactions, tumors, trauma, and causes. Currently there are few reports about these conditions.
The periungual folds, 1 proximal fold and 2 lateral folds, are important parts of the nail apparatus, having 2 functions, to protect the matrix and to provide support to the nail plate.
The proximal nail fold is an important part of the nail because of its 2 functions. It serves as a waterproof barrier that protects the nail from any injury that may occur through the cuticle, The proximal nail fold is additionally important because of the formation of the nail plate through the dorsal matrix in the segment below its ventral portion, which influences the growth direction, making it grow in an oblique direction over the nail bed, and the microcirculation that provides useful information about some pathologic conditions.
It is also called vallum unguis or nail wall, and is an extension of the dorsal part of the skin of the digits from which 2 epithelial surfaces originate, the dorsal and the ventral. It has a structure similar to that of the adjacent skin without dermatoglyphics or sebaceous glands and has 3 parts: the glabrous skin, the cuticle that is the horny product of the proximal nail fold that adheres to the dorsal surface of the nail plate, and the ventral portion called eponychium.
The proximal nail fold can be affected by different disorders such as congenital, systemic and infectious (bacteria, viruses, fungi, parasites) diseases, drug reactions, dermatoses, trauma, malignant and benign tumors, reactions to trauma and other disorders that can affect the fold in one or all of the nails and toenails.
Among the alterations that can be observed at the level of the cuticle are hangnails ( Fig. 1 ), which are common in children and people who bite their nails, and that can or cannot be accompanied by small erosions ( Fig. 2 ), various types of dyschromia such as the one with blackish discoloration that can be of racial type ( Fig. 3 ), chronic renal failure ( Fig. 4 ) due to drug reactions ( Fig. 5 ), melanocytic nevi ( Fig. 6 ), ink of pen or markers ( Fig. 7 ), tattoos ( Fig. 8 ), phytophotodermatitis ( Fig. 9 ), trauma ( Fig. 10 ), or other signs such as gentian violet coloration ( Fig. 11 ).
Paronychia or perionyxis is among the most frequent diseases of the proximal nail fold. It can be acute or chronic, caused by bacteria such as S taphylococcus and less commonly by Streptococcus beta-haemolyticus and gram-negative enteric bacteria, and it can also affect the lateral folds of finger and toenails.
Its acute form is characterized by erythema, edema, heat, pain, and purulent secretion; occasionally it forms a subungual abscess ( Fig. 12 ). It may follow a break of the skin caused by manicure injury ( Fig. 13 ), the use of artificial nails, a prick from a thorn, a torn hangnail, or onychophagia. It generally affects 1 single nail. The differential diagnosis should be made with other periungual inflammations such as chronic eczema ( Fig. 14 ), herpes simplex, psoriasis ( Fig. 15 ), Reiter disease, and acute ischemia when the finger is cold. Acute paronychia is more common in patients with onychophagia.
Chronic paronychia is not considered a primary infection. It is often associated with multiple factors, such as irritants or allergens, and seen in people who keep their hands in constant humidity and use detergents, soaps, and different chemicals. Thus it is more common in housewives; cooks; laundresses; pastry chefs; cleaning staff; women who cook tortillas; children who suck their fingers; patients in contact with acidic substances or alkalis; barmen; fishmongers; and patients with diabetes, psoriasis, in peritoneal dialysis, or with colostomy (these last two because of the continuing washing patients do during their treatment). Some paronychias can be considered as an occupational condition and involve acute exacerbations that may be caused by infections by Candida or Pseudomonas . There may be erythema, edema, and exudates in one or more folds. In advanced cases, there is no cuticle, and this causes a separation from the nail plate that favors secondary infections, edema, and changes in coloration, with alterations of the nail plate, such as Beau lines, onychomadesis and cross-ridges when the alteration affects mainly the lateral folds. On the surface, the nail plate becomes friable and rough, with numerous irregular transverse ridges or waves that appear as a result of repeated acute exacerbations. In warm climates, these chronic forms might be associated with Scytalidium infection.
The occupation of the patient determines which digits will be the most affected. It can be the thumb, the index of the dominant hand, or the middle finger.
The chronic variety has predominance in the nail folds of hands ( Fig. 16 ) and is multifactorial, so it can be secondary to contact, allergic, or hypersensitivity disorders; irritative; or secondary to Candida; and occupational.
Other agents that cause paronychia include oral retinoids ( Fig. 17 ), cephalexin, protease inhibitors such as lamivudine, indinavir, and cytostatics like docetaxel, 5 fluorouracil, methotrexate, cyclophosphamide, and vincristine, and intralesional injections of bleomycin ( Fig. 18 ).
Among dermatologic diseases, autoimmune bullous diseases like pemphigus vulgaris ( Fig. 19 ) and bullous pemphigoid ( Fig. 20 ) can be found that can manifest with bullae or erosions depending on the evolution of the disease. Other cutaneous diseases include psoriasis with its characteristic erythemato-squamous plaques ( Fig. 21 ), atopic dermatitis ( Fig. 22 ), lichen simplex cronicus ( Fig. 23 ), and granuloma annular ( Fig. 24 ).
Among the nail fold alterations caused by systemic diseases are purpura by infiltration of the bone marrow, infection with HIV ( Fig. 25 ), hemorrhagic dengue ( Fig. 26 ), vasculitis ( Fig. 27 ), gout with tophi ( Fig. 28 ), and pseudoporphyria caused by chronic renal failure. Diabetic vascular and neuropathic alterations are predominant at the feet and can manifest as necrosis, ulceration, blisters, and secondary infections ( Figs. 29–31 ). Arterial thrombosis ( Fig. 32 ) may be seen in cryoglobulinemia and the phospholipid syndrome ( Fig. 33 ).
