|Year : 2008 | Volume
| Issue : 2 | Page : 60-64
R Asish1, Sunu Ramachandran2, Anita Balan1
1 Department Oral Medicine and Radiology, Government Dental College, Thiruvananthapuram, India
2 Department Oral Medicine and Radiology, Pariyarum Dental College, Kannoor, India
TC 4 / 1709 (2), MRA-27 Keerthi Lane, Engineering College (P.O), Thiruvananthapuram-695016, Kerala
Source of Support: None, Conflict of Interest: None
| Abstract|| |
Pachyonychia congenita represents a group of rare, autosomal dominant keratin disorders with characteristic nail findings, abnormalities of the palmoplantar skin, pilosebaceous apparatus, oral and laryngeal mucosa and teeth. The main clinical characteristic that gives the condition its name is the abnormally thickened nails. A case with typical clinical features is discussed.
Keywords: Hyperkeratosis of nail bed, leukokeratosis, pachyonychia congenital
|How to cite this article:|
Asish R, Ramachandran S, Balan A. Pachyonychia congenita. J Indian Acad Oral Med Radiol 2008;20:60-4
| Introduction|| |
Pachyonychia congenita (PC) represents a group of rare, autosomal dominant keratin disorders with characteristic nail findings, abnormalities of the palmoplantar skin, pilosebaceous apparatus, oral and laryngeal mucosa and teeth. The hallmark of PC is the hyperkeratosis of the nail bed, which leads to the distal elevation with increased transverse curvature of nail plate. This abnormality results in an omega or pince nail appearance. The nail plates also become friable and discolored. These findings are severe on thumbs, index fingers and toes.
PC is a rare disorder; about 300 cases have been reported so far. Major clinical types of PC are the Jadassohn - Lewandowsky type (PC-1), Jackson - Lawler type (PC-2), Shafer-Brunauer type (PC-3), PC-4. A case of PC-1 which reported to our department is presented.
| Case Report|| |
A 6 year old child was referred from the dermatology clinic for white patches in the oral cavity to the Department of Oral Medicine and Radiology, GDC, Thiruvananthapuram. Patient had consulted the dermatologist for the evaluation of asymptomatic nail changes that was present from the first year of life.
She had slight burning sensation in mouth while taking hot and spicy foods for more than 6 months. There was history of spontaneous shedding and then subsequent regrowth of right fingernail at the age of 2. Medical, drug and family history were noncontributory. There was no history of natal or neonatal tooth, early loss of primary teeth, oral blisters or plantar pain. She consulted a dentist at the age of 3 for removal of badly decayed lower right back milk teeth, the post extraction period was uneventful.
General examination revealed a moderately built and nourished girl with normal posture and gait. On examination, the nails demonstrated hyperkeratosis that was associated with distal elevation and increased transverse curvature of the nail plate, which gave an omega appearance. The nail plates were thick and yellow brown in color. There was keratoderma of knees and erythematous papular lesions of skin [Figure 1],[Figure 4],[Figure 5].
Intraoral examination demonstrated a white non-scrapable keratotic lesion on tongue and accentuation of bite line of buccal mucosa [Figure 2],[Figure 3]. Angular chelitis was also evident.
Routine blood and urine examinations were within the normal limits. Diagnosis of PC was made based on clinical findings. Biopsy of the oral lesions was deferred considering its benign nature.
| Discussion|| |
Pachyonychia congenita is a rare, form of hereditary genodermatoses affecting nails and other ectodermal tissues. ,,,, This is characterized by discoloration and thickening of nails which usually begins with in the first month of life. The main clinical characteristic that give the condition its name is the abnormally thickened nails (Pachy=thick; nychia=nails). The term Pachyonychia congenita tarda (PCT) has been suggested by Paller et al . for the late onset form of PC. ,, PC was originally described by Wilson in 1905. In 1906, Jadassohn Lewandowsky reported the association of the disorder with palmoplantar keratoderma and other ectodermal defects. ,
Both sexes are affected equally, no pattern of occurrence has been found as to ethnicity or nationality. Hypertrophy and yellowish brown discoloration of the nails, hyponychial hyperkeratosis is present at birth or becomes apparent at the first year of life. ,, Hyperkeratosis and hyperhydrosis of palm and soles, acral bulla, follicular keratosis and oral leukokeratosis is also seen early in life. ,, Oral lesions presents as thickened white or grayish-white plaques on the dorsum of tongue. Buccal mucosa and palate may also be affected.
PC is caused by genetic mutations in genes that encode keratin proteins specific to the epithelial tissues. , On an average of 50% of the off springs of an affected person will inherit the disorder. The possibility of transmission of the mutate copy of gene of PC is 50% for each pregnancy.
Munro was the first to propose the genetic defect in PC located to keratin gene cluster in chromosome 17 in 1994.  In his detailed biologic analysis in 1995, McLean revealed that PC was caused by mutation in encoding the epidermal keratinocyte keratins K6a, K6b, K16 or K17.  Jadassohn-Lewandowski type (PC-1) is affected by mutation in gene encoding keratin 6a (Protein K6a, gene KRT6a) or keratin 16 (Protein K16, gene KRT 16). ,,,,,,, Jackson-Lawler (PC-2) type is caused by mutation in keratin 6b (protein K6b, gene KRT 6b) or keratin 17 (protein K17, gene KRT 17). Cockayne expressed the opinion that presence of an additional factor (second genetic mutation) is necessary for the expression of disease. ,,
Four clinical subtypes of PC have been described so far. PC1, Jadassohn - Lewandowsky is the more frequent variant. , The nails are thickened and brownish with gray surface. All finger and toe nails are affected. The thickened finger nails may expand into periungal tissue causing paronychia. ,,, The skin lesions consist of follicular hyperkeratosis of face and extensor aspects of proximal portion of extremities. Circumscribed or diffuse hyperkeratosis of palm and soles, periodic development of blister, hyperhidrosis are other characteristic features. ,,, Oral cavity affected by leukokeratosis demonstrated as patchy white areas on tongue and buccal mucosa. ,,
PC2, Jackson-Lawler syndrome is less common variant, characterized by hypotrichosis, thickened nails, natal teeth and pilosebaceous cyst. ,, Oral leukokeratosis occurs less frequently in PC-2.
PC-3, Shafer-Brunauer type, angular chelitis and corneal dyskeratosis are the important features. PC-4 shows features of other types along with laryngeal involvement and mental retardation.
Molecular DNA analysis reveals deletion and substitution mutation and other mutation of keratin genes. ,,, Prenatal diagnosis can be done by chorionic villous sampling. , Oral biopsy confirms leukokeratosis.
The hyperkeratotic lesions of skin and oral mucosa show acanthosis, hyperorthokeratosis and parakeratosis. Premalignant changes are, however, not observed.
The electron microscopy shows thickened and clumped intermediate filaments and keratohyaline granules. The thick clusters of tonofilaments and keratohyaline granules were present in granular layer. The spinous layer tonofilaments are found at the periphery of cells. There are no features pathognomonic of the disease.
In babies, PC is misdiagnosed as candidosis. ,, The occasional detection of few candidal spores but no hyphae excludes onycomycosis.
Dyskeratosis congenita is a rare congenital x-linked recessive trait characterized by atrophy and reticulated pigmentation of skin, dystrophy of nails and oral leukoplakia and progressive pancytopenia, which usually appears in childhood. ,
The most striking feature the of skin is hyper or hypo pigmented macules or reticulated patches. Thinned, tapered, distorted and dystrophic nails are another characteristic finding. Shedding of nails occurs usually after the age of 5. ,,
Mucosal leukoplakia is commonly seen on buccal mucosa, tongue and oropharynx. Other mucosal sites are also affected like oesophagus, anus, vagina and glans penis. Hyperhidrosis of palms and soles, aplastic anaemia, splenomegaly and mental retardation are other manifestations. Malignant neoplasm of skin, mouth, rectum and cervix has been reported.
Hereditary benign bntraepithelial byskeratosis (HBID)
A rare autosomal dominant condition, usually present in early life with bulbar conjunctivitis and whitish oral lesions. ,, Oral lesions consist of soft, asymptomatic white folds and plaques of spongy mucosa. The commonly affected areas are buccal and labial mucosa, labial commissures, floor of the mouth and lateral aspect of tongue, gingiva and palate. ,,, Oral lesion are generally detected in first year of life. The condition is self-limiting and it requires no treatment.
White sponge nevus
It is an autosomal dominant condition and is due to a mutation in keratins 4 and 13. , The lesion clinically appeared as asymptomatic, deeply folded white or gray thickenings with spongy texture.
Intraoral lesion, affects bilaterally on buccal mucosa in the form of keratosis appears that early in the life. A variable degree of involvement of other mucosal sites esophagus, vulva and vaginal mucosa occurred while conjuctival mucosa is spared. ,,,,, There is no specific treatment for this particular condition as it is asymptomatic and no risk for malignant potential.
Oral leukokeratosis is not a pre-cancerous lesion and is usually asymptomatic. The lesion is usually discovered on routine oral examination. The superadded candidosis is managed by antifungal therapy.  Retinoids are used to help in the differentiation and protection of epithelial tissues. The dystrophic nails are treated with keratinolytic agents like salicylic acid. The severely affected nails are removed surgically. 
Advancements in delivery systems, availability of RNA reduction agents, gene slicing approaches may improve, make the ultimate goal of target gene correction of PC more feasible in future. ,,
Pachyonychia congenital (PC) a rare genetic disorder of autosomal dominant trait. The dentists often get consulted for the oral leukokeratosis usually present in PC. Awareness of its benign nature can alleviate the apprehension in patient.
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[Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5]