Pachyonychia Congenita ICD-10: Q84.5

Genetic skin disorder

Often searched as: super thick toenails, painful calluses on feet, nails that won't grow normal, thick nails genetic condition, hard skin on soles of feet, nails turning yellow and thick, painful feet walking condition, nail deformity from birth…

Clinical urgency level

lowmediumhigh

Systems Affected

nailsskin (palms and soles)hair folliclesoral mucosa

Severity Levels

mild

Nail thickening only or mild plantar keratoderma with minimal pain; limited impact on daily function.

moderate

Painful calluses on feet affecting walking, nail dystrophy on multiple digits, follicular cysts, and oral leukokeratosis.

severe

Debilitating plantar pain preventing normal walking or standing, extensive nail loss, widespread cysts, and significant quality of life impairment.

Red Flags

Calluses so painful that walking becomes impossible
Signs of infection in thickened nail or skin areas (pus, increasing redness, fever)
Rapidly worsening nail dystrophy in a child
White oral patches that change in appearance or ulcerate
Skin cysts that become inflamed, painful, or grow rapidly

Clinical Presentation

Severe nail dystrophy in pachyonychia congenita

Source: Wikimedia Commons (CC BY-SA 3.0 )

Plantar keratoderma in PC — painful sole calluses

View gallery on DermNet NZ (image gallery reference)

When to See a Doctor

See a dermatologist or geneticist if you or your child have thickened nails from an early age combined with painful calluses on the soles, especially if walking is affected. Genetic testing can confirm the diagnosis and guide management. Oral white patches should also be evaluated.

Differential Diagnosis

Onychomycosis (fungal nail infection — very common mimicker)
Psoriatic nail disease
Yellow nail syndrome
Palmoplantar keratoderma (other subtypes)
Darier disease
Leukoplakia (oral white patches)

Comorbidities

Recurrent skin infections in callused areas
Natal or prenatal teeth (in some subtypes)
Follicular keratosis
Chronic pain and reduced mobility
Depression and anxiety related to chronic pain and appearance

Prognosis

PC is a non-life-threatening but lifelong condition. It does not improve spontaneously and tends to remain stable or worsen gradually with age and mechanical stress. There is no approved cure, though siRNA-based gene silencing therapies are in clinical development. Symptom management — especially plantar pain — is the primary focus. Quality of life is significantly impacted, particularly by foot pain, which can prevent participation in normal daily activities.

Detailed Overview

Causes, Symptoms, and When to Take Action Pachyonychia congenita (PC) is a rare genetic disorder primarily affecting the skin and nails. Symptoms usually begin in early life and vary in severity. How It Looks Texture: Thickened, dystrophic nails; hardened callused areas on the soles and palms Color: Nails may appear yellowish or discolored; skin may show areas of hyperkeratosis Shape: Nails grow abnormally, with thick plates or flared edges; calluses may appear as well-defined, thick skin areas Location: Nails (fingernails and toenails), soles of the feet, sometimes palms, areas of friction (hips, knees, waist) Other features may include cysts under the skin, bumps around hair follicles, and white patches on the tongue or inside cheeks. Why Does It Appear? Caused by mutations in one of several keratin genes, which disrupt the structure and function of skin, nails, and hair structures The disorder is typically inherited in an autosomal dominant pattern, though some cases arise spontaneously Even normal mechanical stress (walking, pressure) can lead to breakdown of skin cells, causing painful calluses Should You Be Concerned? PC is not malignant, but it can cause chronic pain, disability, and reduced quality of life Painful calluses may limit walking or mobility Nail deformities may become severe and affect appearance Secondary complications such as infections in thickened skin regions can occur Evaluation by a dermatologist or genetic specialist is advised for diagnosis and management. Can You Prevent It? There is no known way to prevent PC, since it is a genetic condition. However, measures may reduce complications: Reducing friction or pressure on affected skin areas Maintaining foot care and protective footwear Monitoring for secondary issues (blisters, infections) 👉 How Piel AI Can Help Piel AI can help monitor changes in nails, skin thickness, and callus formation over time. While not diagnostic, it supports observation of progression, response to care measures, and assists in communication with medical professionals. Summary Pachyonychia congenita is a hereditary disorder affecting nails and skin, often manifesting with thickened nails and painful calluses. It is caused by mutations in keratin genes and is autosomal dominant. Though noncancerous, it can cause pain, functional limitations, and complications. Supportive care, protection, and monitoring are central to management.

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