What are the possible causes of nail brittleness?

Causes of Nail Brittleness

Nail brittleness results from a combination of intrinsic factors (systemic conditions, nutritional deficiencies, medications, inflammatory diseases) and extrinsic factors (environmental damage, occupational moisture exposure, trauma), with idiopathic brittle nail syndrome being the most common diagnosis after excluding secondary causes. 1

Primary Categories of Causes

Systemic and Nutritional Deficiencies

• Iron deficiency anemia causes brittle nails with longitudinal ridging and splitting, and can manifest as koilonychia (spoon nails) even before anemia develops 2
• Biotin deficiency is a recognized nutritional cause, with supplementation showing 63% clinical improvement in affected patients 1
• Thyroid dysfunction should be screened as a potential aggravating factor 1
• The British Journal of Dermatology recommends screening for systemic conditions including thyroid function tests and complete blood count to identify underlying causes 1

Inflammatory Dermatologic Conditions

• Psoriasis produces nail thinning with subungual hyperkeratosis and longitudinal ridging 1
• Lichen planus causes thinning of the nail plate with subungual hyperkeratosis and longitudinal ridging 1
• These inflammatory conditions can be distinguished from simple aging by associated nail changes such as pitting, onycholysis, or discoloration 1

Medication-Induced Causes

• Taxanes (docetaxel and paclitaxel) cause onychorrhexis, ridging, thinning, and nail fragility as a dose-dependent toxicity 1
• Other chemotherapeutic agents including capecitabine, etoposide, cytarabine, cyclophosphamide, and doxorubicin may cause mild to moderate nail changes 1
• Targeted therapies such as mTOR inhibitors, EGFR inhibitors, or MEK inhibitors can also cause nail alterations 1

Infectious Causes

• Fungal infections (onychomycosis) present with thickening, discoloration, and friable texture, accounting for 15-40% of all nail diseases in adults 1
• Chronic paronychia from Candida infection leads to proximal nail dystrophy with associated ridging, commonly occurring with occupational moisture exposure 1
• Pseudomonas aeruginosa (Green Nail Syndrome) causes green discoloration and nail damage 1

Environmental and Occupational Factors

• Progressive dehydration of the nail plate from environmental and occupational factors plays an important role in nail brittleness 3
• Chronic moisture exposure damages the nail matrix and causes chronic paronychia with subsequent ridging 1
• Trauma from nail biting, use of nails as tools, prolonged water soaking, and exposure to harsh chemicals contributes to brittleness 1

Diagnostic Approach

Clinical Examination Priorities

• Examine nail texture: soft and friable suggests fungal infection, while hard and brittle suggests non-infectious causes 2
• Assess for paronychia (nail fold swelling/erythema) which suggests Candida infection, particularly with occupational moisture exposure 1
• Look for associated changes including pitting, onycholysis, subungual hyperkeratosis, or discoloration that suggest inflammatory disease rather than simple aging 1
• Check for koilonychia (spoon-shaped nails) as a classic sign of iron deficiency 2

Laboratory Testing When Indicated

• Mycological confirmation is essential before diagnosing fungal infection, as 50% of dystrophic nails are non-fungal despite similar clinical presentation 2
• Potassium hydroxide (KOH) preparation with microscopy is the first-line screening test to visualize fungal elements 1
• Screen for systemic conditions with thyroid function tests and complete blood count 1
• Monitor ferritin levels when iron deficiency is suspected 2

Critical Pitfalls to Avoid

• Do not assume fungal infection without laboratory confirmation—the nail surface in non-infectious conditions typically doesn't become soft and friable as in fungal infection 1
• Do not overlook iron deficiency as a significant contributor to nail dystrophy, especially when documented 2
• The most common cause of treatment failure is incorrect diagnosis based solely on clinical grounds without laboratory confirmation 1
• Neglecting occupational counseling is a pitfall—patients with chronic moisture exposure need guidance on protective measures like wearing gloves while cleaning 1