Clinical Terminology for Ingrown Toenails
The clinical term for ingrown toenails is onychocryptosis (also known as unguis incarnatus), which describes the condition where the nail edge grows into and pierces the periungual dermis, causing inflammation and pain 1, 2.
Definition and Clinical Characteristics
Onychocryptosis refers specifically to the pathological process where the lateral edge of the nail plate penetrates the surrounding nail fold tissue 3. This condition:
- Most commonly affects the hallux (great toe) in approximately 70% of cases occurring between ages 12-30 years 4
- Results from the nail plate piercing the perionychium, inducing secondary periungual inflammation 3
- Presents with pain, erythema, edema, and potential formation of friable granulation tissue on the lateral nail folds 3
Distinction from Related Conditions
It is critical to distinguish onychocryptosis from paronychia, though they can coexist 3:
- Paronychia describes painful erythematous inflammation with swelling and tenderness of the lateral nail folds, which can progress to mimic ingrown nails 3
- Onychocryptosis specifically refers to the mechanical process of nail plate invasion into periungual tissue 3
- Drug-induced paronychia (particularly from EGFR inhibitors) can lead to thinning of the periungual stratum corneum, which may result in secondary onychocryptosis 3
Common Clinical Pitfall
Never confuse onychocryptosis with onychomycosis (fungal nail infection), as these are entirely different conditions requiring different management 3. Onychomycosis presents with nail thickening, discoloration, and onycholysis (nail plate separation from the nail bed), whereas onychocryptosis involves mechanical invasion of tissue by the nail edge 1, 2.