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 Table of Contents  
REVIEW ARTICLE
Year : 2020  |  Volume : 9  |  Issue : 2  |  Page : 55-59

Nail: A mirror to systemic diseases in children


1 Department of Pediatric Gastroenterology, KMCT Medical College, Calicut, Kerala, India
2 Dermatologist, IQRAA Community Hospital, Vazhakkad, Kerala, India
3 Department of Dermatology, KMCT Medical College, Calicut, Kerala, India
4 Dermatologist, Moulana Hospital, Perinthalmanna, Kerala, India

Date of Submission29-Oct-2020
Date of Decision10-Nov-2020
Date of Acceptance29-Nov-2020
Date of Web Publication27-Apr-2021

Correspondence Address:
Dr. A Riyaz
Department of Pediatric GE, KMCT Medical College, CALICUT, Kerala
India
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/jpai.jpai_26_20

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  Abstract 


Nail is rightly regarded as a mirror to systemic diseases. Nails serve as a valuable diagnostic tool as it is very easy to examine all 20 of them quickly. A careful examination of nails may give vital clues to underlying sinister diseases evidenced by alteration of their shape, size, color, or texture. This review may help pediatricians to suspect an underlying serious systemic disease just by a careful examination of nails.

Keywords: lunula, matrix, nail, nail bed, nail plate, nail unit, systemic diseases


How to cite this article:
Riyaz A, Faiz R A, Riyaz N, Roshin R A. Nail: A mirror to systemic diseases in children. J Pediatr Assoc India 2020;9:55-9

How to cite this URL:
Riyaz A, Faiz R A, Riyaz N, Roshin R A. Nail: A mirror to systemic diseases in children. J Pediatr Assoc India [serial online] 2020 [cited 2022 Dec 9];9:55-9. Available from: http://www.jpai.in//text.asp?2020/9/2/55/314813



The nail consists of several parts including nail plate (The visible hard part of nail), the nail bed (Skin beneath the nail plate), matrix (Only living part of the nail and which produces keratin and cells), the cuticle or eponychium (Tissue that overlaps the plate and rims base of the nail, protecting the matrix), nail folds (Skin folds that frame and support the nail on three sides), and lunula (Whitish, half-moon shaped area at base of nail underneath the plate).

The nail serves several functions including protection of the distal digit, for scratching and grooming, and improvement of fine touch. It also helps in picking up of small objects besides enhancing the esthetic appearance of the hand.[1]

Toenails grow at the rate of 1 mm/month, while fingernails grow at the rate of 3 mm/month. The regrowth of fingernail takes about 6 months, toenails 12 months, and big toenail 18 months. Thus, the fingernails grow approximately three times faster than toenails, and those on the dominant hand outpace those on the nondominant one. The growth of nail may be interrupted by several factors, such as anticancer therapy, trauma, severe systemic diseases, and advancing age.[2]

As clinical signs of toenails are often modified by trauma, we get better information from examination of fingernails.[3] Nails should be examined under adequate lighting without glare and with magnification in natural light. If there is a subtle change in pigmentation due to vascular lesions, it may decrease on applying pressure.

Systemic diseases causing nail changes may be classified based on abnormal color, abnormal shape, and abnormal surface [Box 1].[4],[5]



Abnormal color

Healthy nails are generally pinkish in color. In leukonychia, one or more fingernails and/or toenails appear partially or completely white in color. Leukonychia associated with systemic disease may be true or apparent. Mees' lines (Aldrich/Reynold's lines) represent true leukonychia due to arsenic poisoning. They were described by the Dutch Physician R. A. Mees in 1919. However, the Englishman E. S. Reynolds in 1901 and the American C. J. Aldrich in 1904 had made earlier descriptions.[6],[7],[8]

These are transverse single or multiple white lines that may extend the complete width of the nail plate. They may be seen on a single digit or multiple digits. As the pathology is in the nail plate but not in nail bed, they migrate toward the distal end of the nail plate over time. Causes other than arsenic poisoning include Hodgkin's disease, leprosy, tuberculosis, malaria, herpes zoster, chemotherapeutic drugs, and poisoning with antimony and thallium.[9]

Muehrcke's lines are apparent leukonychia described by the American Physician Robert C. Muehrcke in 1956. They are double transverse white bands that run parallel to the lunula across the entire width of the nail. They represent an abnormality of the nail vascular bed. Hence, they disappear temporarily when the distal digit is squeezed unlike Mees' lines because the abnormal blood supply is compressed. They may be found in any condition that causes severe persistent hypoalbuminemia such as nephrotic syndrome, kwashiorkor, protein losing enteropathy, and decompensated chronic liver disease. They tend to disappear when the serum albumin level becomes normal and reappear if it falls again. They are usually found on the second, third, and fourth fingernails. Unlike Beau's lines, Muehrcke's lines are grooved. The thumb is usually not affected by Muehrcke's line unlike Mees line.[10]

Terry's nails are apparent leukonychia in which the proximal 80% of the nail becomes opaque while the remaining 20% retains the normal pink color. Hence, it is also called “80 and 20 nail.” The condition involves all nails evenly and lunula will not be seen. It was described by Dr. Richard Terry in 1954.[11]

About 80% of the patients with severe liver disease have Terry's nails, but they may also be found in patients with other systemic diseases, such as congestive heart failure, renal failure, and diabetes mellitus. The pathogenesis is not clear but may be due to changes in nail bed vascularity. They are usually seen in fingernails, but toenails may also be affected. Usually, all nails are affected, but occasionally, only a single nail may be affected. Terry's nails can also appear as a natural sign of aging even without any underlying systemic diseases.

Half-and-half nails or Lindsay's nails are also apparent leukonychia and are commonly seen in chronic kidney disease. It may rarely be due to Kawasaki disease, cirrhosis, Crohn's disease, hyperthyroidism, zinc deficiency, chemotherapy, Behçet's disease, HIV infection, and pellagra. The proximal 50% of the nail has a dull, white, ground-glass appearance, while the remaining 50% is brownish. Hence, it is also called semilunar nails. The exact pathogenesis is not known. The proximal white color may be due to anemia of renal failure, while the distal brownish color may be due to melanin deposits. Bean described it first in 1963, while Lindsay coined the term half-and-half nail in 1967.[12]

Blue lunulae may be seen in 8% of patients with Wilson's disease.[13] Other causes include prolonged treatment with minocycline, azidothymidine, busulfan, phenolphthalein, and systemic 5-FU.

Red lunulae may be seen in psoriasis, alopecia areata, carbon monoxide poisoning, systemic lupus erythematosus (SLE), cardiac failure, chronic obstructive pulmonary disease (COPD), cirrhosis, etc.[14] It may merge with the nail bed in the distal part of the lunula or be demarcated by a pale line and can be obliterated by pressure on the nail plate.

Yellow nail (xanthonychia) syndrome is a very rare condition characterized by yellow nails, lymphedema, bronchiectasis, and pleural effusion reported by Heller in 1927. The lunula is obscured, and there is increased transverse and longitudinal curvature with loss of cuticle and notable hump. Other features include cross-ridging, very hard (scleronychia), and difficult-to-trim nail, and disappearance of cuticle.[15]

In splinter hemorrhage, there is capillary injury in the longitudinally oriented epidermal–dermal ridges, which manifests clinically as small linear hemorrhages resembling wood “splinters” in the nail. The blood which attaches itself to the underlying nail plate moves distally. Infective endocarditis is the most common systemic disease associated with splinter hemorrhages. Its significance as a sign of endocarditis is more if associated with other features of infective endocarditis such as fever, Roth's spots, Osler's nodes, Janeway lesions, or a heart murmur. Other causes of splinter hemorrhage include trauma, vasculitis, cirrhosis, trichinellosis, scurvy, chronic glomerulonephritis, and Darier's disease.[16]

The presence of periungual telangiectasia is an important clue to underlying SLE, systemic sclerosis, and dermatomyositis. Other causes include diabetes mellitus, COPD, and rheumatoid arthritis.[17]

Abnormal surface

Beau's line (nail matrix arrest) is a nonspecific reaction to any serious systemic disease or event that is severe enough to disrupt the growth of the nail, such as meningitis, pneumonia, and Kawasaki disease [Box 2]. It was described in 1846 by the French Doctor Joseph Honoré Simon Beau.[18] It manifests as transverse grooves or furrows on the surface of the nail plate several weeks or more after onset of the precipitating event. It first appears at the distal edge of the lunula and moves forward as the nail grows. As normal nails grow at the rate of 3 mm/month, the onset of the illness can be guessed by the width of the furrow and its distance from the cuticle.



Beau's lines of the fingernails appear by 4 weeks of life in almost 90% of neonates and disappear before 14 weeks. This may be due to intrauterine distress or physiological alterations during birth.[19]

Pitting (Rosenau's depression) is usually due to pathology of proximal matrix. It is seen in psoriasis, alopecia areata, and eczematous dermatitis.

Trachyonychia (sandpaper nail) is defined as roughness of the nails due to excessive longitudinal ridging. The nails appear as if they have been sandpapered in the longitudinal direction. As it may affect all nails, it is also called 20-nail dystrophy. Causes of trachyonychia include psoriasis, alopecia areata, and nail lichen planus. It is commonly misdiagnosed as onychomycosis.

Onychoschizia (nail splitting) causes horizontal splits within the nail plate. It is usually associated with onychorrhexis characterized by longitudinal splitting of the nail plate and these two are together called “brittle nail syndrome.” Frequent wetting and drying of the hands are the most common predisposing factors. Hence, it is common among house cleaners, nurses, and hairdressers. It may also be seen in diabetes, hypothyroidism, hypopituitarism, Sjögren's syndrome, and severe malnutrition, in addition to skin diseases such as psoriasis and lichen planus.

Abnormal shape

Clubbing (watch-glass nails, drumstick fingers/Hippocratic nails/Trommelschlägelfinger)

Clubbing, described by Hippocrates almost 2500 years back in a patient with empyema, is regarded as the oldest clinical sign in medicine.[20] It is very important for clinicians to pick up early clubbing because it may be the forerunner of an underlying sinister systemic disease.

It is characterized by increased curvature of nail plate both longitudinally and transversely and also increased sponginess of the soft tissues at the base of the nail. It develops initially in the thumb and forefinger followed by the other fingers. Clubbing is usually acquired and often reversible. It is bilateral and painless unless associated with hypertrophic osteoarthropathy, which is very rare in children.[21]

The “profile sign” helps to pick up early clubbing. The Lovibond's angle (profile angle/ungual–phalangeal angle) located at the junction between nail plate and proximal nail fold is normally less than 160°. Clubbing causes thickening and edema of the nail bed that lifts the nail, thereby making the Lovibond's angle more than 160°. This also leads on to the development of fluctuation of the nail bed. Later, the angle may be entirely lost and the nail plate and skin lie in a straight line (180° angle). With progressive clubbing, the angle may exceed 180°, and finally, the profile of the fingertip becomes bulbous. Obliteration of the Lovibond's angle is the first sign and also the most constant feature of clubbing. The onset of clubbing is usually a poor prognostic sign as the underlying illness has usually reached an advanced stage by then.[22]

Schamroth's sign or Schamroth's window test originally demonstrated by the South African Cardiologist Leo Schamroth, when he was hospitalized with infective endocarditis, is another useful test for clubbing. When the distal phalanges of corresponding fingers of opposite hands are directly opposed, there is a small diamond-shaped “window” between the nail beds. In clubbing, this window is obliterated.

The exact mechanism of clubbing is still obscure, and hence, there are several postulates. Normally, megakaryocytes which are continuously released from the bone marrow are trapped by the pulmonary capillary bed and fragmented into platelets. In any situation which causes changes in pulmonary vasculature such as left-to-right shunts, suppurative lung diseases, and cirrhosis, megakaryocytes pass into the systemic circulation intact. These large particles tend to travel in an axial stream and preferentially land in the tips of the fingers and toes. When megakaryocytes are stuck in the smaller capillaries, they can secrete platelet-derived growth factor (PDGF). This can cause several effects such as acting as a growth factor and increasing vascular permeability. Thus, the high concentrations of PDGF at the fingertips may be responsible for clubbing.[23]

Other postulates include tissue hypoxia, genetic factors, and a neurocirculatory reflex. Neurocirculatory reflex leads to increased blood flow through multiple arteriovenous shunts in the distal phalanges. Increased blood flow then leads to tissue hypertrophy and hyperplasia.

Pseudoclubbing is defined as an increased curvature of the nails in both the longitudinal and transverse axes, with preservation of the normal Lovibond's angle. Causes include nail bed tumors and inflammatory disorders such as psoriatic arthritis that affect the distal phalangeal bone.

Koilonychia or spoon nail is a condition in which the normal transverse convex curvature of the nail plate becomes concave. Hence, it is actually the converse of clubbing. A simple test is that it could hold a drop of water on its surface without spilling. One of the classic causes is iron deficiency anemia. It may be a normal finding in infants in the big toes and tends to disappear within the first few years of development. However, it is more commonly seen as an occupational change in nails and may also be idiopathic.[24]

Some of the rare causes include trauma, Raynaud's disease, hypothyroidism, SLE, and nail–patella syndrome. A rare variant of koilonychia is the “ongle en fermoir d' épingle de nourrice” in which the deformity is shaped like the catch on a safety pin.[25]

Platynychia is characterized by an abnormally flat and broad nail and may be seen as part of an autosomal dominant condition in which multiple nail abnormalities may be seen. However, the most important cause is iron deficiency anemia. If anemia is not corrected, it may progress to koilonychia.

Anonychia or micronychia involving thumb and index fingers present since birth is seen in nail–patella syndrome (iliac horn syndrome/hereditary onychoosteodysplasia/Fong's disease) caused by mutations in the LMX1B gene, located in chromosome 9q34. The classic tetrad of this disease includes dysplastic nails, hypoplastic or absent patellae, dislocation of the radial head, and the presence of iliac horns.[26]

In macronychia, the nails of one or more digits are wider than normal. This may be an isolated defect or may be associated with megadactyly, as in type 1 neurofibromatosis, tuberous sclerosis, and proteus syndrome.

Dolichonychia is a condition in which the length of nails greatly exceeds its width and is seen in Marfan syndrome, Ehlers–Danlos syndrome, hypohidrotic ectodermal dysplasia, and hypopituitarism.[27]

The pincer nail (incurved nails, unguis constringes, trumpet nail, or omega nail) is a dystrophy of the nail caused by an enlarged base of the distal phalanx, characterized by excessive transverse curvature of the nail plate along its long axis. The term “pincer nail” was introduced by Cornelius and Shellery in 1968.[28]

Miscellaneous

Koenen's tumors (garlic-clove fibromas) are subungual or periungual fibromas appearing as erythematous, polypoid, digitated smooth, firm papules and nodules, in tuberous sclerosis complex. They are usually 5–10 mm in length but occasionally may be quite large. Periungual fibromas are more common than subungual fibromas.[29] They are not seen in children, appear by 12–14 years, and gradually increase in size with age.[30] They are more commonly seen on the toenails than on the fingernails.

Poor nail growth is a feature of yellow nail syndrome, lipoid proteinosis (Wiethe Urbach syndrome), and various types of ectodermal dysplasias.[31]

Dyskeratosis congenita is a very rare genetic disorder of telomere maintenance characterized by a triad of dystrophy of the nails, leukokeratosis of the oral mucosa, and extensive reticulate pigmentation of the skin. Nail changes are the first manifestation, leading to splitting, dystrophy, and shedding of nails.[32]

Turtle back nail is seen in Fabry disease (angiokeratoma corporis diffusum), a rare multisystem X-linked recessive disease due to deficiency of the enzyme ceramide trihexosidase.[33]

Pachyonychia congenita is a very rare autosomal dominant genodermatosis characterized by defective keratinization, nail dystrophy, follicular hyperkeratosis, painful palmoplantar blisters, and oral leukokeratosis. It is of two types – type 1 ( Jadassohn-Lewandowsky syndrome More Details), and type 2 (Jackson-Lawler syndrome) due to mutations in genes encoding five differentiation-specific keratins 6A, 6B, 6C, 16, and 17.[34]

Plummer's nail or onycholysis (separation of nail from nail bed) occurs in hyperthyroidism or trauma. It is also a classic feature of psoriasis.[35]

Pterygium unguis is characterized by a scarring involving the nail fold extending onto the matrix. In dorsal pterygium, the proximal nail fold fuses to matrix and later to nail bed. It is seen in lichen planus, cicatricial pemphigoid, dyskeratosis congenita, graft versus host diseases, SLE, etc., In ventral pterygium, a distal extension of the hyponychium attaches to the undersurface of the nail plate thus obliterating the distal nail groove. It is seen in leprosy, neurofibromatosis, subungual exostosis, SLE, and systemic sclerosis.[36]


  Conclusion Top


Nail diseases are relatively rare in children, but they are a source of great anxiety for the parents. Rarely, nail lesions may be the first manifestation of a genetic disorder, and in this case, it is usually associated with other skin or mucosal involvement. A careful history followed by a meticulous clinical examination often helps the clinician to distinguish between different conditions and to decide on the correct management. Examination of the nails should be an essential part of pediatric physical examination. Medical teachers should stress upon their students the importance of examination of nails right from their undergraduate days.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.



 
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