Pediatricians encounter a vast array of nail disorders in clinical practice. Basic knowledge of the common nail disorders is pivotal for assessment, diagnosis, and referral when necessary. Nail pathology can result from focal or systemic abnormalities. The nail can be directly affected by localized infection, inflammation, mechanical forces, or trauma. Alternatively, nail pathology can result from nutritional deficits, genetic abnormalities, systemic disease, and medication or toxin exposures.
Nails are functional, structural, and cosmetic components of human anatomy. The nail plate is a translucent arrangement of compressed, keratinized dead cells. Nail folds are specialized epithelium that provide structure and protect the nail plate and matrix. The lateral nail fold is the paronychium, and the proximal nail fold is called the eponychium or cuticle. Underlying the eponychium is the nail matrix that contains the germinal cells. It takes 20 days for the fingernail and 80 days for the toenail to emerge from the matrix. Matrix to free edge growth for the fingernail is close to 6 months and 12 to 18 months for the toenail. This growth interval is important to consider for the timing of a potential insult and deciding the treatment course.
Key Points in the History
• Cyanotic congenital heart defects, chronic lung disease, and gastrointestinal disorders are associated with digital clubbing.
• Dermatological disorders such as psoriasis, eczema, alopecia areata, and lichen planus are associated with nail pitting and dystrophy.
• Disease states and certain medications, such as Kawasaki disease, hand–foot–mouth disease, pneumonia, prolonged high fevers, and chemotherapy, can cause a temporary growth arrest in the nail that is later manifested as Beau lines.
• There are benign familial forms of digital clubbing and koilonychias.
• Given the time it takes for nails to emerge from the matrix and grow, a history of medication or toxin exposure should be retrospective and encompassing.
• Nails are porous, and cosmetic products and frequent washing can strip and weaken the nail.
• Nail salons can be the source of fungal and bacterial nail infections.
• Koilonychia is associated with iron deficiency anemia in the adult population.
• Repeated local trauma can impact the growth and integrity of the nail.
Key Points in the Physical Examination
• In digital clubbing, assess for cardiopulmonary pathology such as murmurs or wheezing.
• Lovibond angle, the angle of eponychium to the nail plate, is normally 160 degrees. Clubbing induces angles of greater than 180 degrees.
• Schamroth window is the normal space that is seen when the dorsal aspects of opposing fingers are aligned. This diamond-shaped space is absent in clubbing.
• Dermatologic disorders such as psoriasis, eczema, and lichen planus are associated with nail pitting and dystrophy.
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