Brittle nails are nails showing jagged distal free edge, often with additional splitting of nail plate itself. Splitting may be either in layers or transverse entire nail plate.
Pathogenic factors leading to brittle nails are either factors that impair intercellular adhesion of the corneocytes of the nail plate, or factors that cause a pathologic nail formation by involving the matrix.
- clinical features of brittle nails are onychoschizia and onychorrhexis: the impairment of intercellular adhesive factors of the nail plate is expressed as onychoschizia the involvement of the nail matrix is expressed as onychorrhexis
- characterized by lamellar splitting of the free edge and distal portion of the nail plate
- may vary from mild parallel furrows of the superficial layers of the back surface of the nail plate at the distal free edge to severe lamellar splitting of the complete free edge and at least one third of the distal part of the nail plate
- characterized clinically by longitudinal thickening and thinning or ridging of the nail plate
Causes of brittle nails include
- secondary to impairment of intercellular adhesive factors of the nail plate
- exogenous factors
- immersion/desiccation - in occupations such as nursing, and hairdressing, where repetitive wetting and drying of the hands
- chemicals - in particular, occupational exposure to thioglycolates, solvents, cement, acids, alkalis, anilines, salt, and sugar solutions
- trauma - for example typing, telephone dialing, improper nail clipping (also trauma caused by excessive length of the nails)
- fungi - fungal infections may cause both intracellular and intercellular fractures in the nail plate
- secondary to pathologic nail formation
- causes of pathologic nail formation resulting in brittle nails include:
- endocrine and metabolic diseases such as hypopituitarism, hyperthyroidism and hypothyroidism, hypoparathyriodism, acromegaly, diabetes mellitus, gout, osteoporosis, osteomalacia, pregnancy, and malnutrition (anorexia nervosa, bulimia)
- decreased nail formation has been observed after radiation or arsenic intoxication
- reduced vascularization and oxygenation directly affect epidermal growth and keratinization
- conditions that have been associated with brittle nails in this context include, arteriosclerosis and age-related decrease of circulation, microangiopathy, Raynaud's disease, anaemia, polycythaemia vera (polycythaemia causing sludge formation), major chronic infectious diseases (pulmonary tuberculosis, empyema, bronchiectasis), and sarcoidosis
- disordered keratinization may impair nail plate formation
- if a self-limiting impairment of short duration, nail pits or spots of leuconychia may be seen
- involvement of the entire nail plate or longitudinal involvement occur secondary to processes that have impaired the nail matrix during prolonged periods - conditions that may cause such involvement include Darier's disease, pityriasis rubra pilaris, lichen planus, and alopecia areata - these conditons may cause longitudinal ridges, longitudinal splits, or sandpaper-like nails
- psoriasis, atopic dermatitis, and mycoses may lead to a thickened nail plate with a brittle appearance
- nail growths/tumours (such as melanoma, squamous cell carcinoma, warts) are diagnosed after removal of the nail plate - however the nail plate may show longitudinal abnormalities indicative of brittlenes
Reference:
- van de Kerkof PC et al Brittle nail syndrome: a pathogenesis-based approach with a proposed grading system. J Am Acad Dermatol. 2005 Oct;53(4):644-51