Acute Koilonychia of Fingernails due to Lye

Dear Sir,

Koilonychia (spoon-shaped nails) is characterized by the reversion of the curvature in the transverse and longitudinal axes of the nail plate. The lateral edges become upwards everted and the nail appears thinner and concave, giving rise to the typical “spoon” shape [1,2].

An 80-year-old woman presented with an acute onset of koilonychia and yellow-reddish discoloration of all fingernails (Fig. 1a, b). The sudden occurrence was cause of concern for the patient and prompted her to seek medical advice.

Fig. 1.

a Clinical presentation of koilonychia and pigmentation of all fingernails. b Lateral view highlighting the curvature. c Complete healing after 3 months.

Her medical history was unremarkable for systemic or cutaneous diseases, and she denied any medication at the time of our consultation; however, she reported direct contact with wet ivy ash 2 days earlier, having cut the ivy and then burnt it to use as fertilizer. Unfortunately, after a few days of rain, the patient decided to collect it with her bare hands. The following morning, the nail plates of all her fingernails presented a yellow pigmentation and were curved in the classic spoon-shaped appearance, typical of koilonychia. We hypothesized that the ash and water produced an alkaline substance, namely lye, which thinned and softened the nail plates, making them easily deformable.

We prescribed the daily application of a nail lacquer made of a hydroalcoholic extract (Equisetum arvensis), which is on sale in Italian drugstores, to harden the nail plate. In addition, we advised the patient to avoid contact with irritating substances as well as trauma. After 3 months, the clinical manifestation completely resolved (Fig. 1c).

Normally, the nail is firmly attached to bone by vertical dermal connective tissue bundles in the subungual area, which bond directly to the periosteum. Koilonychia is most frequently due to local rather than systemic factors (Table 1). Occupational koilonychia is often associated with mild nail plate surface abnormalities and nail plate discoloration/pigmentation [1,2].

Table 1.

Common causes of koilonychia

Idiopathic
Physiological	Early childhood
Congenital	LEOPARD syndrome
	Ectodermal dysplasias
	Trichothiodystrophy
	Nail-patella syndrome
Acquired	Metabolic/endocrine	Acromegaly
		Hemochromatosis
		Iron deficiency
		Porphyria
		Renal dialysis/transplant
		Thyroid disease
	Dermatoses	Alopecia areata
		Darier disease
		Lichen planus
		Psoriasis
		Raynaud disease
	Exogenous	Occupational
		Traumatic
	Infections	Onychomycosis
		Syphilis
	Carpal tunnel syndrome

Lye, properly known as potassium hydroxide (KOH), is an alkaline solution obtained by leaching ashes (largely containing potassium carbonate). The role of KOH in dermatology is well known, being used in higher concentration to dissolve keratin in mycological examination or in lower concentration as a softener for nail grooves.

Lye can be produced both via warm or cold method. In the cold method, ash and water are conserved for days in a container and mixed daily, allowing the caustic salt of the ash to be released (the more mixture is mixed, the longer the contact and the more the solution will be caustic). Koilonychia due to alkali has been reported in cement workers/bricklayers [2,3]. In our case, the contact between ash and water lasted only a few days, so the lye was not powerful; however, the direct contact with the alkaline substance determined the loss of consistency of the nail plate, which was deformed because of the traction exerted by the nail bed, becoming spoon-shaped.

Statement of Ethics

Written consent has been obtained from the patient. The authors have no ethical conflicts to disclose.

Disclosure Statement

The authors have no conflicts of interest to disclose.