Introduction:
Pachyonychia congenita is an inherited disorder that causes abnormal keratinization. Keratin is found in the outermost layer of the skin and body. It strengthens the skin to prevent any penetration of harmful substances through the skin. Keratinisation is the process of formation and deposition of keratin in the outermost layer of the skin. Palms and soles are areas with a thick layer of keratin deposition. Pachyonychia congenita is a condition where the soles, palms, and nails are thickened, and white patches are found in the mucous membrane. Pachyonychia congenita is characterized by painful palmoplantar keratoderma, hypertrophic nail dystrophy, blistering, oral leukokeratosis, palmoplantar hyperhidrosis, and follicular Keratosis.
What Is Pachyonychia Congenita?
Pachyonychia is a condition that affects the skin and the nails. It is expressed in the first years of life, and affected individuals show nail dystrophy; that is, the fingernails and the toenails become thick and are abnormally shaped. The palms and soles also become thickened, and blisters and calluses are formed on the soles of the feet. This is called palmoplantar keratoderma. The formation of blisters can make it difficult for the individual to walk. It is also known as :
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Jackson-Lawler syndrome.
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Congenital pachyonychia.
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Jadassohn-Lewandowski syndrome.
What Is the Cause of Pachyonychia Congenita?
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It is a rare disorder that occurs due to the mutation of genes K6a, K6b, K6c, K16, and K17. These genes are responsible for making keratin. Keratin is responsible for providing strength to tissues such as skin, nails, and hair. Mutations in the genes affect the keratin proteins, which makes the skin cells fragile and prone to damage. The skin becomes less resistant to trauma and friction. This results in skin cells breaking down by even everyday activities such as walking, causing blisters and callus formation. Defective keratin can also impair the normal structure and function of hair follicles and nails.
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It is an autosomal dominant disorder. That is, only one pair of defective genes is necessary for the condition to be expressed. An affected individual has a 50 % chance of passing the defective gene to their offspring.
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It can affect all ethnic groups.
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It affects both sexes with equal predilection.
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In some cases, patients can exhibit the disorder without any relevant family history; this occurs due to sporadic mutations during conception.
What Are the Clinical Features?
Since multiple genes can cause the condition, pachyonychia congenita has different clinical features depending on the gene affected.
Palms and Soles:
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Palms and soles are thickened, or callous formation is noticed, which can cause difficulty in walking. This is called palmoplantar hyperkeratosis or keratoderma.
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Focal palmoplantar keratoderma: blister formation below the keratoderma causing intense pain. The pain may require using a cane, crutches, or even wheelchairs.
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The pain may be severe in patients that have mutated K6a and K16 genes; the pain is constant in nature.
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95 % of patients with pachyonychia may have neuropathic involvement.
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Keratoderma may be accompanied by hyperhidrosis (excessive sweating of palms and soles).
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In patients with gene K6c mutation, the only clinical feature of pachyonychia congenita is focal palmoplantar keratoderma.
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Warm weather and friction can precipitate blisters.
Nails:
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Pachyonychia congenita is characterized by the thickening of nails. Of the mutations, K6a and K16 have the most expressed nail changes.
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Hypertrophic nail dystrophy: It is noticed in the first few years of life. Nails grow to full length and then have an upward slant, or the nails terminate prematurely, leaving an exposed digital fingertip.
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The nails have a brownish discoloration.
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The changes in nails are evident from birth, as the name suggests.
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The toenails are less affected, but all the fingernails are affected.
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Some K16 mutation fingernails are not affected.
Dry Skin:
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Follicular hyperkeratosis is seen in friction sites such as knees and elbows, making these areas dry. The condition becomes less pronounced in adult life.
Cysts:
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Pilosebaceous and steatocystoma cysts are common. Steatocystoma is a widespread cyst that is filled with sebum.
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Cysts may sometimes cause pain.
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Patients with K17 gene mutations have steatocystoma multiplex.
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Cysts are often found in the armpits, groin, scalp, or back.
Larynx:
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Hoarseness of voice is seen due to airway obstruction due to laryngeal involvement.
Oral Lesions:
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Natal or prenatal teeth are a typical feature of K17 gene mutations. Natal teeth are a condition where the child has teeth at birth.
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Leukokeratosis- keratin deposition is seen as white patches on the tongue and cheeks. This might be misdiagnosed as candida infections.
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Angular Cheilitis- inflammation in the sides of the tongue may be seen in children.
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Children with K6a may experience pain when they first begin to eat, called first bite syndrome.
Follicular Keratosis:
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Bumps form around the hair follicles on the elbows, waistline, and knees.
How Is Pachyonychia Congenita Classified?
The condition can be broadly classified into type 1 and type 2. The classification is done based on clinical features. When the mutations are present in the K6a gene, it is classified as PC-K6a. Similarly, mutations in K6b mutations are PC-K6b and so on.
How to Diagnose Pachyonychia Congenita?
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The clinical appearance is the first step in diagnosing pachyonychia congenita.
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It can be confirmed by molecular genetic studies. In molecular genetic studies, mutations in the keratin genes are detected.
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Genetic counseling is advised for affected individuals since it is a genetically inherited disease.
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Prenatal testing can be done in women whose partner is affected. In ‘test-tube’ embryos, a preimplantation diagnosis can be made.
How to Treat Pachyonychia Congenita?
Since it is a genetic condition, it does not have curative treatment. Instead, the treatment is based on the symptom and their severity, such as:
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Palmoplantar keratoderma requires the feet to be groomed in order to reduce hyperkeratosis (thickness of the keratin). However, trimming can cause pain.
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Blisters should be punctured with a sterile needle; this drains the fluid, making the lesion dry.
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Podiatry: Thickened nails are trimmed, and length is reduced; this is done to prevent infections. Nails can be soaked to soften them to make the trimming easier.
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Mechanical Debridement: Calluses have to be trimmed to prevent difficulty in walking and to lessen pain.
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Oral leukokeratosis can be managed by maintaining good oral hygiene. Gentle brushing can remove the white appearance. However, vigorous brushing can cause more Keratosis, as the body recognizes it as a trauma. Oral antibiotics have been found to have some improvement.
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Follicular Hyperkeratosis: Alpha hydroxy acid creams and lotions can have a keratolytic effect.
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Leukokeratosis with laryngeal involvement may require surgical correction to reestablish the airway; if not, it can be life-threatening.
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Cysts: The cysts require incision and drainage. Antibiotics are administered to prevent infection. If necessary, cysts are excised.
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Prevention of secondary complications include the use of sterile instruments, antibiotic administration, and bleach bath.
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Moisturizers and emollients can be used to soften the skin. Emollients such as lanolin or vaseline can be used.
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Bleach baths can be done to reduce infection.
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Salicylic acid, urea, and other keratolytic agents can be used.
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Cushioned footwear can be worn.
What Is the Prognosis?
Pachyonychia does not have any systemic effects; being a genetic condition, it lasts life long but does not affect the lifespan of the individual. However, the quality of life is affected due to the psychological impact and the functional impairment caused by the disease.
Conclusion:
Pachyonychia congenita is a condition that predominantly affects the nails, skin, and hair. The defective genes cause abnormal function and structure of keratin. This makes the nails thicken, increases the keratin deposition in palms and soles, and causes blister and callus formation. It is an autosomal dominant disorder. Symptomatic treatment is given to manage the disease conditions, and this can improve the quality of life of the individual.
