Nail psoriasis: symptoms and treatment

Nail psoriasis is an immune-mediated inflammatory disorder of the nail apparatus that can affect the nail matrix, the nail bed, or both. Typical manifestations include pitting, onycholysis, oil spots, subungual hyperkeratosis, longitudinal and transverse grooves, and splinter hemorrhages. Nail involvement occurs in a significant proportion of people with cutaneous psoriasis, and the vast majority of patients develop signs of psoriasis over the course of their lives. This impairs hand and foot function, appearance, and quality of life, and is often associated with the development of psoriatic arthritis. [1]

The clinical picture reflects the anatomy: matrix changes produce punctate depressions, leukonychia, crumbling, and red spots in the lunula; nail bed changes include onycholysis, subungual hyperkeratosis, "oil" spots, and "splinter" hemorrhages. This distinction is critical for treatment selection and goals. [2]

The connection with joints is no coincidence: the nail is anatomically linked to the extensor enthesis of the distal interphalangeal joints, so nail changes often occur alongside enthesitis and may anticipate psoriatic arthritis. In real-world practice, this is a reason to actively seek symptoms of joint damage and refer the patient to a rheumatologist. [3]

How to recognize: a clinic without fog

The basis remains an examination under good lighting, assessing all fingernails, toenails, skin, and scalp. Dermoscopy of the nails is helpful during the examination: the characteristic signs of psoriasis and differences from fungal infections increase diagnostic accuracy and help select the appropriate site for testing. [4]

It's important to remember the frequent coexistence of fungal infections: some patients with nail psoriasis actually have onychomycosis. Therefore, in cases of subungual hyperkeratosis, onycholysis, and nail discoloration, mycological examination is routinely performed, and in doubtful cases, polymerase chain reaction or periodic acid-Schiff staining on nail sections. [5]

Modern methods detect fungi more quickly and sensitively than traditional culture: polymerase chain reaction is superior to culture in sensitivity and reduces response time from weeks to hours, although it can detect non-viable microorganisms and requires clinical evaluation. This should be discussed with the patient before initiating antifungal therapy. [6]

Table 1. Clinical signs by source of lesion

Source of defeat	Typical signs	What does a dermatoscope see?	Comments for treatment
Nail matrix	Pinpoint depressions, leukonychia, crumbling, red spots in the lunula	Multiple irregular pits, lunula changes	Drugs that penetrate the matrix are needed, sometimes injections into the proximal ridge
Nail bed	Onycholysis, oil spots, subungual hyperkeratosis, splinter hemorrhages	Onycholysis with "spikes", yellow-orange spots, vascular pattern	Emphasis on anti-inflammatory drugs and keratolytics, injections to the bed are possible
[7]

Diagnostics

1. Clinical verification and photographic documentation. Assessment of all nails, skin, and scalp, questionnaire on arthritis symptoms. Dermoscopy of the nails to look for "oil spots" and "spikes" in onycholysis. [8]
2. Exclusion of onychomycosis before starting long-term anti-inflammatory therapy: microscopy with potassium hydroxide and culture or staining of cut sections with periodic acid-Schiff; in controversial cases - polymerase chain reaction for dermatophytes and yeasts. [9]
3. In cases of pain in the distal interphalangeal joints and minimal external changes, ultrasound of the nail and enthesis is used to search for subclinical enthesitis and thickening of the nail apparatus structures; this helps in early management of the risk of arthritis. [10]
4. Basic stratification of nail lesion severity using the Nail Psoriasis Severity Index (NAPSI) and its modifications for the starting point and monitoring of dynamics during therapy. [11]

Table 2. Diagnostic algorithm for nail psoriasis

Step	Target	Method	When is it mandatory?
Examination and dermatoscopy	Confirm phenotype and localization	Clinical examination, dermatoscope	Always on the initial visit
Exclusion of fungus	Don't miss onychomycosis, which changes tactics	Potassium hydroxide, culture, staining, polymerase chain reaction	In case of subungual hyperkeratosis, onycholysis, discoloration
Search for enthesitis	Early detection of arthritis	Ultrasound of the nail and enthesis	Pain in the distal joints, stiffness, “numb” nail changes
Severity assessment	Base point and effect control	NAPSI Index, Modified NAPSI, N-NAIL scale	Before treatment and every 12-24 weeks
[12]

How to Measure Severity: Indexes That Speak in Numbers

The Nail Psoriasis Severity Index (NAPSI) divides the nail into four quadrants and separately considers signs of nail matrix and nail bed involvement. The total score reflects the severity and number of affected nails; the tool is convenient for clinical and research use. [13]

The modified NAPSI index refines the contribution of the matrix and nail bed for each nail and better reflects clinically significant changes. In recent years, more precise diagnostic scales have been discussed, such as the N-NAIL, which demonstrates improved diagnostic accuracy. [14]

Table 3. Severity scales for nail psoriasis

Scale	What does it measure?	Range	Where is it useful?
NAPSI	Matrix and bed features in 4 quadrants	On the nail and in total on the hand and foot	Routine clinic, research
Modified NAPSI	Score breakdown of nail features	Higher sensitivity to changes	Monitoring treatment response
N-NAIL	Diagnostic scale for distinguishing phenotypes	Threshold values for verification	Screening and research
[15]

What nail psoriasis is not: differential diagnosis

It's most often confused with onychomycosis. Both can cause onycholysis and subungual hyperkeratosis, so a clinical examination without a laboratory examination is a common cause of error. Dermoscopy is helpful: with a fungal infection, a "ruin pattern" and "spikes" from the proximal edge of the detachment are visible, but laboratory confirmation is essential before antifungal treatment. [16]

Other "doubles": lichen planus, eczema of the nail folds, chronic trauma, and the effects of manicures and artificial nail adhesives. Allergic contact dermatitis to cyanoacrylates can cause onycholysis and paronychia, worsening the condition. [17]

Table 4. Is it nail psoriasis or not?

State	For	Against	What will confirm
Nail psoriasis	"Oily" spots, pits, "splinter" hemorrhages, connection with skin psoriasis	No fungi in the tests, negative culture	NAPSI index, dermatoscopy, negative mycological tests
Onychomycosis	Ruin pattern, spikes, dense hyperkeratosis	There are no typical pits or oil stains	Potassium hydroxide, culture, polymerase chain reaction
Lichen planus	Veins, longitudinal cracks, thinning	There are no "oil" stains	Biopsy when in doubt
Allergic contact dermatitis with adhesives	Onycholysis and paronychia after nail extensions or glue	No systemic psoriasis	Exposure cancellation, patch testing
[18]

Treatment

General measures always work: keeping nails short, wearing gloves when doing wet work and gardening, regularly moisturizing nail folds, avoiding aggressive manicures and nail extensions, minimizing trauma, and wearing proper footwear. This reduces the Koebner phenomenon, decreases onycholysis, and facilitates the application of medications. [19]

Topical treatments are the first step for limited lesions. Very strong corticosteroids are used in occlusive courses, along with the retinoid tazarotene, vitamin D analogs, and sometimes calcineurin inhibitors applied to the nail folds. Combinations of corticosteroids and vitamin D accelerate the response. Phototherapy with psoralen and ultraviolet A is helpful for some patients, but the effect is slow to develop and may cause nail discoloration. [20]

Injections into the nail fold are a viable option for severe lesions of 1-2 nails, especially those with matrix pathology. Triamcinolone acetonide is most commonly administered in small doses at intervals of several weeks; there is also evidence of the effectiveness of local methotrexate or cyclosporine. Pain, skin atrophy, and hematomas are monitored; an experienced practitioner can reduce these risks with proper technique. [21]

Systemic non-biological agents are appropriate for multiple nails, complex lesions, and concomitant psoriatic arthritis. Methotrexate is the most common, significantly reducing nail manifestations, although the response develops gradually due to slow nail plate growth. The choice of systemic therapy is based on current recommendations from European guidelines and international expert consensus. [22]

Small molecules with a good tolerability profile—the phosphodiesterase inhibitor apremilast—provide sustained reductions in nail psoriasis severity scores and improvements in nail ultrasound imaging by 24-52 weeks; for the selective tyrosine kinase 2 inhibitor, there is growing data in complex sites, including nails, including real-world use. The decision is made by a dermatologist, taking into account comorbidities. [23]

Biological therapy is the most powerful tool for severe and refractory nail disease. Interleukin 17 inhibitors show rapid and high nail responses, sustained for 1-2 years; tumor necrosis factor and interleukin 23 inhibitors are also effective, with some molecules demonstrating superiority over adalimumab in improving nail performance. The choice of molecule depends on the associated manifestations, safety, and patient preference. [24]

Table 5. Treatment ladder for nail psoriasis

Scenario	What to do first	What's next?	When to escalate
1-2 nails, function is not affected	Topical occlusive care	Injections into the proximal ridge for the matrix phenotype	No progress within 12-24 weeks
Lots of nails or severe discomfort	Topical + systemic non-biological drug	Switching to biological therapy in case of insufficient response	In case of ineffectiveness or intolerance
Psoriatic arthritis or "high-impact" areas	Systemic therapy immediately	Biological therapy targeting nails and joints	With active joint symptoms
[25]

Table 6. Facts about biological therapy and nails

Drug and target	Research and timing	Key result for nails
Secukinumab, anti-interleukin 17A	A randomized study with a follow-up of up to 2.5 years	Significant and sustained reduction in nail psoriasis severity index, superiority over placebo at week 16, and maintenance of effect in the long term
Ixekizumab, anti-interleukin 17A	A subgroup of patients with nails in a large study	Significant improvement in nail psoriasis severity index by week 12 and accumulation of effect by week 60
Guselkumab, anti-interleukin 23	Comprehensive analysis of regional manifestations	Better or comparable nail responses compared with adalimumab at 24-48 weeks
Adalimumab, an anti-tumor necrosis factor	Data for 24 weeks and longer	Marked improvement in nail index in a significant proportion of patients
Generalized by classes	Network meta-analyses of recent years	At the start, nail manifestations are most quickly reduced by interleukin 17 inhibitors; by the year, several molecules from different classes maintain a high chance of a profound response.
[26]

Care and prevention

Keep your nails short, avoid pushing back your cuticles, wear gloves when cleaning and gardening, moisturize your hands and nail folds, and choose shoes that won't irritate your nails. Avoid nail extensions and avoid acrylate-based adhesives, as they can cause allergic onycholysis and paronychia. [27]

In cases of pruritic onycholysis, the proximal edge can be temporarily fixed with adhesive tape to reduce microtrauma, and if a secondary infection occurs, short courses of local antiseptics can be administered as prescribed by a doctor. Do not scrape the subungual material, as this will worsen the detachment. [28]

When to see a doctor without delay

If nails are rapidly shedding, there is pain in the distal joints, morning stiffness, severe subungual hyperkeratosis, suppuration, or an unpleasant odor, or if multiple nails are affected and interfering with work, these are reasons to seek an in-person consultation. For severe cases, effective systemic and biological therapies are available, which now provide profound answers to nail and joint problems. [29]