What are the common systemic conditions associated with nail abnormalities that I should be aware of in my practice?

Common systemic conditions associated with nail abnormalities include psoriasis, thyroid disorders, connective tissue diseases, and nutritional deficiencies. Psoriasis is a frequent cause of nail changes such as pitting, onycholysis, and subungual hyperkeratosis, reflecting its systemic inflammatory nature ¹. Thyroid dysfunction, both hypo- and hyperthyroidism, can lead to brittle nails, onycholysis, and slow nail growth due to altered metabolism and circulation ¹. Connective tissue diseases like systemic lupus erythematosus and scleroderma may present with nail fold capillary changes and dystrophic nails, indicating microvascular involvement ¹. Nutritional deficiencies, particularly of iron, zinc, and biotin, can cause brittle, spoon-shaped (koilonychia), or ridged nails, highlighting the importance of systemic nutritional status (Cedirian et al., 2024). Additionally, chronic respiratory and cardiovascular diseases may manifest as clubbing, a notable nail abnormality linked to systemic hypoxia ¹. Recognising these associations in general practice is crucial for early identification and management of underlying systemic conditions ¹ (Cedirian et al., 2024).