Is a condition in which the angle between the nail and the nail bed is 180 degrees or greater?

Koilonychia (spoon nails)

The nail plate is thinned and flattened with upward eversion of its lateral and distal edges, leading to a concave spoon-like shape (seeFig. 71.2). Koilonychia, especially of the 2nd–4th toes in young children (1–4 years of age), is physiologic and eventually resolves spontaneously. In adults, koilonychia is rare and occurs in association with severe iron deficiency5 and systemic amyloidosis. It can also be seen in manual laborers who have contact with irritants and detergents that damage the nail plate.

KOILONYCHIA

Koilonychia is the name given to spooning of the nails where the lateral distal edges of the nail plate are elevated above a depressed center. In some cases there is peripheral hyperkeratosis under the everted edges of the nail. When koilonychia is viewed laterally the nail plate resembles the bowl of a spoon, and hence the common name ‘spoon nails’. Although there are many case reports in the literature of conditions associated with koilonychia, two main categories surface: Congenital/hereditary forms (see Chapter 15) and acquired forms. In the acquired forms, endocrinological causes such as hypothyroid and iron deficiency anemia lead the way (see Chapter 15), followed by occupational/ traumatic forms where the distal edge may be curved (see Chapter 18).

Koilonychia (Spoon Nails)

Spoon nails are thin and concave, with the edges everted so that if a drop of water were placed on the nail, it would not run off (Fig. 33.44). Koilonychia may result from faulty iron metabolism and is one of the signs of Plummer-Vinson syndrome, as well as of hemochromatosis. Spoon nails have been observed in coronary disease, syphilis, polycythemia, and acanthosis nigricans. Familial forms are also known to occur. Other associations include psoriasis, lichen planus, Raynaud syndrome, scleroderma, acromegaly, hypothyroidism and hyperthyroidism, monilethrix, palmar hyperkeratoses, and steatocystoma multiplex. A significant number of cases are idiopathic. Manual trauma in combination with cold exposure may result in seasonal disease. Sherpas are Tibetan people living in the Nepalese Himalayas, who often serve as porters on mountain-climbing expeditions. Chronic cold exposure, in combination with hypoxemia, may contribute to the high frequency with which koilonychia is observed among them and people living in the Leh Ladahk region of India.

Walker J, et al: Koilonychia. J Eur Acad Dermatol Venereol 2016; 30: 1985.

Yanamandra U, et al: Ladakhi koilonychia. BMJ Case Rep 2014 Jan 16; 2014.

Physiologic Aspects of the Nail in Pediatric Population

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Koilonychia describes nails with a transverse and/or longitudinal concave nail dystrophy with a central depression. The term “spoon nails” describes the flattening in the middle with everted lateral edge.8 It is frequently idiopathic in newborns, especially on the big toe (Fig. 5.1), and spontaneously regresses when the nail plate thickens with age.

Transient light-brown or ochre pigmentation of the proximal nail fold and dorsal digit to the interphalangeal joint is more typical of dark-skinned newborns. It is a physiologic melanic pigmentation appearing in the first 6 months of life characterized by a regular reticular pattern located only in the periungual tissue without involvement of the cuticle or nail unit.9

Chevron or herringbone nails, where the nail plate surface shows oblique and longitudinal diagonal ridges converging toward the center of the nail plate at the distal part, describing a central spine with an appearance of “V” shape or a chevron. It appears between the age of 5 and 7 years and disappears in early adulthood.10

Transient physiologic onychoschizia is mainly noted on the big toes and thumbs with transverse and lamellar splitting at the free edge in early infancy.11

Beau’s lines of the fingernails appear at 4 weeks of life in 92% of newborns and disappear with growth in 14 weeks. They result from an intrauterine distress or physiologic alteration during birth.11

Iron Deficiency Anemia

Iron deficiency is the cause of 75% of all anemias in pregnancy, and its prevalence may be as high as 47%.57,58 Clinical symptoms include easy fatigue, lethargy, and headache. Pica, which may involve the ingestion of clay, dirt, ice, or starch, is a classic manifestation of iron deficiency and was significantly associated in one study with lower maternal Hb but not with adverse pregnancy outcomes.59 Clinical findings include pallor, glossitis, and cheilitis. Koilonychia has been associated with iron deficiency anemia but is a rare finding. The laboratory characteristics of iron deficiency anemia are a microcytic, hypochromic anemia with evidence of depleted iron stores, low serum iron, high TIBC, low percent saturation, and low serum ferritin. If a bone marrow examination is performed, stainable iron is found to be markedly depleted or absent. Although iron supplementation has not been consistently shown to alter perinatal outcome, the Centers for Disease Control and Prevention strongly recommends screening and treatment of iron deficiency anemia in pregnancy.7,60,61 The rationale is that treatment maintains maternal iron stores and may be beneficial for neonatal iron stores.7

The specific treatment is oral iron, most commonly, in the United States, ferrous sulfate, 325 mg one to three times daily. The WHO recommends 60 mg iron daily with folic acid for all pregnant women but does note that 30 mg may be sufficient.62 A recent trial, in which 43% of the pregnant women had anemia, showed that 30 mg of iron with micronutrients had the same beneficial effect on hemoglobin as 60 mg without micronutrients.63 Other iron preparations are more expensive and do not offer any advantage over ferrous sulfate if equal amounts of elemental iron are given. Reticulocytosis should be observed after 7 to 10 days of therapy, and the Hb can rise by as much as 1 g/wk in severely anemic individuals. Absorption from the gastrointestinal tract can be enhanced by the administration of 500 mg of ascorbic acid with each dose of iron. Gastrointestinal side effects associated with iron therapy include nausea, vomiting, abdominal cramps, diarrhea, and constipation. These symptoms correspond to the dose of elemental iron ingested; if symptoms are troublesome, the dose of iron should be reduced. Ferrous sulfate syrup (300 mg/5 mL) is an effective way of tailoring the dose to the patient's tolerance. Once the anemia has resolved, the patient should continue to receive iron therapy for an additional 6 months to replace iron stores. Vitamin B6 deficiency should be considered in women unresponsive to oral iron therapy, as vitamin B6 normally decreases in pregnancy and supplementation with B6 and iron was associated with an increase in hemoglobin.64

Nail Disorders

Nail abnormalities can be congenital or acquired and may caused by developmental, traumatic, inflammatory, infective, and neoplastic disorders or by medications. The diagnosis of nail dystrophies usually relies on a careful clinical examination and an accurate history, but radiographic or magnetic resonance imaging investigation of the digit and pathology may be required.

Spoon Nail

Spoon nail (koilonychia) is a common deformity in which the normal contour of the nail is lost. The nail is thin, depressed, and concave from side-to-side, with turned-up distal and lateral edges. Koilonychia of the hallucal nails is common in newborns and young infants and resolves spontaneously during childhood. The condition may be a secondary feature of several dermatologic disorders. It occurs in association with nail thickening in psoriasis, onychomycosis, and PC, in which subungual thickening from the hyponychium changes the direction of nail growth. Koilonychia can also be seen in disorders with nail thinning or ridging such as in lichen planus, trachyonychia, and focal dermal hypoplasia. Spoon nails have been described in individuals with severe iron-deficiency anemia, although the pathomechanism is unclear. Koilonychia may also be inherited as an isolated autosomal dominant trait. Koilonychia can be confused with platyonychia, or flattened nails, which have been described primarily in patients with cirrhosis, and with pincer nails, characterized by excessive curvature at the lateral aspects of the nail plate, leading to an appearance of ingrown nails. Pincer nails are usually a congenital deformity but can be acquired in individuals with epidermolysis bullosa, digital epidermoid cysts, and distal phalangeal exostosis. Because they can be quite painful, pincer nails are often corrected surgically.

Isolated malformations

Clubbing and spooning (koilonychia) of the nails may occur as autosomal-dominant abnormalities with no other anomalies (Fig. 8.46). Congenital ingrown toenails may result from congenital malalignment of the great toenails and resolve only with surgical realignment, but most cases are self-limiting and not related to an anatomic nail defect (Fig. 8.47). In the spontaneously regressing type, the ingrown nail may result from transient hypoplasia of the toenails, particularly the great toenails, which usually resolves within 12–18 months. Nail changes may be exacerbated by external trauma and recurrent/chronic paronychia.

Koilonychia

There are many hypotheses concerning the cause of koilonychia (spoon nails). One is that spooning occurs when the distal matrix is angled downward in relation to the proximal matrix. The reverse anatomic association would produce clubbing. Another hypothesis relates this dystrophy to softening and thinning of the nail plate.

Spooning of the nails is a frequent, but temporary, finding in infants. Iron deficiency anemia (Plummer–Vinson syndrome) is classically thought to be the most frequent cause (Fig. 38–3). Replacement therapy usually corrects the disorder. There are three major types of koilonychia: hereditary (autosomal dominant), acquired, and idiopathic. The acquired type is the largest group, most commonly seen in psoriasis, fungal infection, distal ischemia (e.g., Raynaud's phenomenon), and trauma. It may occur in porphyria and hemochromatosis, and occupationally (secondary to softening with oils or soaps). Koilonychia has also been reported in association with carcinoma of the upper gastrointestinal tract.

Faulty Biomechanics and Trauma

Acute trauma to the nail unit can result in onychodystrophy. These nail dystrophies include clubbing, koilonychia (following frostbite or thermal burns), leukonychia, longitudinal melanonychia striata (Fig. 22.7), onycholysis, ridging and splitting of the nail plate, splinter hemorrhages, and subungual hematomas (with or without a fracture of the underlying digit).47–52 Depending on the etiology, the nail changes may be temporary or permanent.

Chronic trauma to the nail unit can result from faulty biomechanics. The normal gait cycle is composed of a stance phase (60%) and a swing phase (40%); the stance phase is divided into contact, midstance, and propulsion periods.53,54 Disease, abnormal development, or trauma can alter the normal biomechanical function of the limb and/or the gait cycle. Some of the bony deformities that can result in a biomechanical abnormality are listed in Table 22.6. The onychodystrophies observed in elderly patients secondary to faulty ambulatory biomechanics are summarized in Table 22.7 (Fig. 22.8).

Shoe-induced biomechanical abnormalities secondary to incompatibility between the foot, its digits, and the shoe can also result in trauma to the toenails and subsequent onychodystrophy. Onychauxis and onychogryphosis may develop from the abnormal growth of the toenails secondary to pressure from the shoes. Subungual hematoma and subsequent onycholysis of that nail may occur in individuals who wear rigid platform shoes or footwear that is too short, because of the repeated trauma to the nail unit during walking. Onychocryptosis and onychoclavus of the 5th toe may also be caused by inappropriate, poorly fitting footwear. In addition, if the distal nail plate becomes worn down by continually rubbing against the inside of the shoe, elderly patients may mistakenly interpret that their toenails do not grow.

Treatment of onychodystrophy secondary to biomechanical abnormalities should be directed toward: (1) the underlying bony abnormality, and (2) the elderly patient's foot care and footwear. Visual and arthritic difficulties are not uncommon in older individuals. These patients might not only have difficulty seeing their shoelaces but may also be unable to bend over and reach the shoes or tie the laces. Footwear with Velcro closures could be used instead of laced shoes. A molded shoe or an orthotic insert that conforms to the shape of the foot is helpful in the nonsurgical management of bony deformities. These modalities can provide adequate shoe fit by comfortably accommodating the existing deformity, by relieving pressure from the deformed joints, and by evenly distributing that pressure over the foot. Soft athletics shoes or sneakers are a less expensive (and less optimal) footwear alternative for elderly patients with bony deformities of the feet.

Other causes of chronic trauma to the nail unit include self-induced habits such as onychotillomania. Onychotillomania is an uncommonly described disorder in which the patient picks off pieces of the nail plate, nail bed, and/or nail folds. One elderly woman claimed that she was ‘merely dissecting and removing tissue which had been destroyed by “minute organisms”’.55

Patients with onychophagia bite the free edge of their nails. They develop short, irregular nails that grow faster than normal. Features that may accompany onychophagia include periungual verruca, ‘hang nails’ (in which small, superficial portions of skin have split away from the lateral nail folds), and recurrent paronychia. In addition, leukonychia striata has been observed in individuals after they have pushed back their cuticles.

The management of patients with onychotillomania and onychophagia can be challenging. Application of distasteful preparations (such as 1% clindamycin, quaternary ammonium derivatives or 4% quinine in petrolatum) onto the nail folds may be helpful to discourage nail biting and chewing. Occlusive dressings can also aid as an adjunctive measure. However, referral of these individuals for psychiatric counseling and treatment should be considered.55,56

Habit tic deformity is another self-induced habit that results in chronic trauma to the nail plate. This condition involves the thumbnails and develops after the individual, consciously or inadvertently, rubs the central portion of the proximal nail fold of the thumb with the ipsilateral index fingernail. This onychodystrophy can be unilateral or bilateral. It appears as central transverse Beau's lines of the thumbnail plate. Spontaneous resolution occurs if the patient stops injuring the corresponding nail matrix.57

Habit tic nail deformity should be distinguished from dystrophia unguium mediana canaliformis. Median nail dystrophy may occur on any fingernail but frequently involves those of the thumbs. It consists of an inverted fir-tree-like split or canal in the nail plate, which is slightly off-center. The nail plate dystrophy extends from the cuticle to the free edge of the nail.58