Brittle nails: pathogenesis and treatment

Journal of Drugs in Dermatology, Jan, 2003 by Hendrik Uyttendaele, Adam Geyer, Richard K. Scher

Brittle nails are a common reason why patients consult a dermatologist. The incidence of brittle nails in the European and North American population is approximately 20%, and women suffer from nail brittleness twice as often as men (1).

There is no concise definition of what constitutes a brittle nail, and there are no characteristic histological findings to help the clinician make this diagnosis. The dermatologist needs to make the diagnosis of brittle nails based on the patient's history and certain non-pathognomonic clinical features. The presenting complaints of patients with brittle nails are often their inability to grow long nails and a description of their nails as soft, dry, weak, or easily breakable. More objective clinical features seen in brittle nails are onychoschizia (transverse splitting), onychorrhexis (longitudinal splitting), and nail plate surface degranulation (2). Brittle nails have been divided into several types including an isolated split at the free edge, lamellar splitting of the free edge, transverse splitting of the lateral edge, and multiple crenellated splitting that resembles the battlements of a castle (3).

Most commonly, a clear-cut etiology for brittle nails cannot be found and hence most cases are labeled as "idiopathic brittleness of the nails." Dehydration due to external influences such as water, detergents, or dehydrating chemicals is often a contributing or causative factor (4). These agents decrease the normal water content of the nail plate, which then results in breakage of the intercellular corneocyte bridges, leading to a fragile and brittle nail plate. Similarly, evaporation of water in the nail plate due to high and low temperatures can result in identical changes (5). Quantitative and qualitative changes in nail keratins may also be induced by chemical and physical insults. Hapalonychia (thinning of the nail plate) due to decrease of the nail matrix length may predispose towards the development of brittle nails. Nails also become more brittle with age. This may be due to the decreased nail growth rates observed in elderly individuals and thus an inherent increased exposure time of the nail plate to environmental factors. Likewise, as skin is drier in the elderly, so too are the nails. A genetic component in the etiology of brittle nails is suggested by the fact that approximately half of patients will report a family member with similar complaints.

Brittle nails may also be found in certain skin diseases such as psoriasis, lichen planus, and alopecia arcata. It is important to recognize these diseases because nail treatment for these disorders are different. Nail brittleness has also been described as an incidental finding in a variety of dermatological disorders such as acanthosis nigricans (6).

It is equally important to rule out systemic etiologies for brittle nails. These include infections such as tuberculosis, endocrinopathies (hypo- and hyperthyroidism (7,8), hypoparathyroidism (9), and pituitary disorders (10)), hypochlorhydria, iron deficiency anemia (11), hemochromatosis (12), arsenical intoxication, glucagonoma (13), osteoporosis, osteomalacia, diseases that cause severe arthritic deformities of the distal joints, Sjogren's syndrome and nutritional disturbances such as cachexia (14), vitamin and zinc deficiencies (15).

The treatment of brittle nails is often difficult. If no precipitating or contributing factors can be elucidated and if the brittle nails have been present for many years, available treatments are often ineffective. However, the initial approach to the treatment of brittle nails should focus on the removal of any exogenous factors that may cause or exacerbate nail fragility. Patients should be instructed not to wash hands frequently and to avoid contact with water or other dehydrating chemicals. Rehydration of the nail plate, cuticle and surrounding nail fold can be obtained by soaking the nails in lukewarm water followed by application of an effective moisturizer. Alpha-hydroxy acid containing moisturizer and preparations that contain hydrophilic substances such as phospholipids have been successfully used for this (16). Occasionally, the once a week use of nail enamel is encouraged to slow water evaporation from the nail plate. It is also recommended that the patients keep their nails short, and clip them after soaking them in lukewarm water.

Numerous therapies have been tried for brittle nails. These include application of essential fatty acids, vitamin c, pyridoxine, iron, vitamin D, calcium, and gelatin (17-19). Several systemic therapies for the treatment of brittle nails have also been tried. Oral iron, primrose oil, pyridoxine and ascorbic acid have been suggested to be of some value (20). More recently biotin, a water-soluble B-complex vitamin, has been demonstrated in several studies to be beneficial in the treatment for brittle nails (21-23). The initial rational for this treatment came from the field of veterinary medicine where biotin had been used for the treatment of pathologic hoof changes in horses (24). An association between deficiency of B-complex vitamins had also been proposed as early as 1940 (25). The recommended daily oral biotin dose is 2.5 mg, with two months being the average time before clinical improvements are observed and the recommended time of treatment is 3-6 months. An increase in nail thickness, decreased lamellar splitting, and decreased irregularities of the dorsal nail plate surface were observed in patients with brittle nails treated with Biotin (21). It is not known how long the improvement in nail strength lasts after cessation of biotin treatment. It also remains unclear how biotin-dependent biochemical mechanisms are responsible for nail plate strength, and whether they are necessary for nail keratin or intercellular cement substance production. Lastly, treatments that would increase the rate of nail growth would be beneficial in the treatment of brittle nails.