A family with pachyonychia congenita affecting the nails only

A family with pachyonychia congenita in which affected individuals showed nail involvement only is described. Pachyonychia congenita is a rare hereditary disorder inherited in an autosomal dominant manner. Various classifications of pachyonychia congenita have been suggested but none indicates nail involvement as a solitary finding.     

Novel and recurrent mutations in the genes encoding keratins K6a, K16 and K17 in 13 cases of pachyonychia congenita

Thirteen patients with pachyonychia congenita types 1 and 2 were studied, two of which had a family history of pachyonychia and 11 of which were sporadic cases. Heterozygous mis-sense or small in-frame insertion/deletion mutations were detected in the genes encoding keratins K6a, K16, and K17 in all cases. Three novel mutations, F174V, E472K, and L469R were found in the K6a gene. Two novel mutations, M121T and L128Q were detected in K16. Similarly, three novel mutations, L95P, S97del, and L99P were found in K17. In addition, we identified recurrent mutations N171del (three instances) and F174S in K6a and R94H in K17. Analysis of both phenotype and genotype data led to the following conclusions: (i) K6a or K16 mutations produce the pachyonychia congenita type 1 phenotype, whereas K17 (or K6b) mutations cause pachyonychia congenita type 2; (ii) the presence of pilosebaceous cysts following puberty is the best indicator of pachyonychia congenita type 2; (iii) prepubescent patients are more difficult to classify due to the lack of cysts; and (iv) natal teeth are indicative of pachyonychia congenita type 2, although their absence does not preclude the pachyonychia congenita type 2 phenotype. This study establishes useful diagnostic criteria for pachyonychia congenita types 1 and 2, which will help limit unnecessary DNA analysis in the diagnosis and management of this genetically heterogeneous group of genodermatoses.     

Pachyonychia congenita tarda. A late-onset form of pachyonychia congenita.

Pachyonychia congenita is an autosomal dominant disorder that usually develops in early infancy. We have observed five patients with the onset of the typical subungual hyperkeratoses of pachyonychia during the teenage years. Leukokeratosis and keratoderma of the palms and soles were associated. The family history of three of the patients suggests that pachyonychia congenita tarda is also inherited in an autosomal dominant manner.     

Pachyonychia Congenita Type I Presenting with Subtle Nail Changes

Abstract:   Pachyonychia congenita type I is an autosomal dominant disorder where nail abnormalities are a constant feature and develop during childhood. We report here a family with pachyonychia congenita type I and very mild nail changes to underline that this diagnosis should be considered even in the absence of severe nail thickening.     

Pachyonychia congenita with laryngeal obstruction

Pachyonychia congenita is a rare genodermatosis that can affect the larynx. Laryngeal obstruction is very unusual with only a few cases reported. A 2-year-old girl presented with typical clinical features of pachyonychia congenita shortly after birth. At age 9 months, following an upper respiratory infection, she developed stridor and hoarseness and was found to have severe laryngeal obstruction, which was felt to be secondary to pachyonychia congenita based on direct laryngoscopy and laryngeal biopsy. Leukokeratosis of her larynx was treated with CO(2) laser on three occasions, with improvement in her respiratory distress after each treatment. This report is the first case of pachyonychia congenita with laryngeal obstruction in which the gene mutation has been established (a deletional mutation in K6a), confirming that laryngeal obstruction can occur in PC-1.     

Pachyonychia congenita tarda

Pachyonychia congenita is a distinct hereditary disorder of keratinization, in which dystrophy of all nails is associated with palmoplantar keratoderma and other hyperkeratoses. Recently a late-onset type has been reported. We report a second family with late-onset pachyonychia congenita, showing a remarkable clinical heterogeneity. Furthermore, one patient demonstrated a number of associated hyperkeratoses not previously recognized. Acitretin proved useful in the treatment of this late-onset form of pachyonychia congenita.     

先天性甲肥厚症Ⅰ型一家系调查

报告先天性甲肥厚症一家系,4代17人中有8人患病,8例患者均于出生后不久即有甲变色,继而甲增厚．2-4岁时出现掌跖角化,局部摩擦后可发生水疱和糜烂。部分患者有舌苔白腻,所有患者均未见胎生齿及脂囊瘤。先证者双肘膝关节毛囊角化性丘疹,足趾及跖部灶性胼胝样角化过度,20甲营养不良。该家系中有2例患者2岁时因突发急性呼吸困难抢救无效而死亡。     

A new type of pachyonychia congenita

We describe two patients with an apparently unique autosomal dominant ectodermal dysplasia. Symptoms consist of thickening of all nails as seen in pachyonychia congenita and severe generalized hypotrichosis. No other abnormalities were present. Histopathological examination of scalp skin showed a reduction in the number of hair follicles, but other abnormalities were not found. Direct sequencing of the keratins known to be associated with pachyonychia congenita, Krt 6a, 6b, 16 and 17, failed to detect mutations. This suggests that this may be a new type of pachyonychia caused by a mutation in a so-called hard keratin.     

Pachyonychia congenita. A clinical, histological and microradiographic study with special reference to oral manifestations.

This paper rresents a clinical, histological and microradiographic study of three patients with pachyonychia congenita with special reference to oral manifestations. The patients, who are relatives, exhibited thickening of finger- and toe-nails, follicular keratosis, palmoplantar keratosis and hyperhidrosis, oral leukokeratosis, and natal teeth. It is stated in the discussion that natal teeth and oral leukokeratosis may constitute the earliest clinical manifestations of pachyonychia congenita and that they appear to accur earlier than nail lesions. When there is a hereditary disposition for pachyonychia congenita, it is important to inspect the oral cavity at an early stage.     

Pachyonychia congenita complicated by hidradenitis suppurativa: a family study

A family is described in which five of the six members with the Jackson-Lawler type of pachyonychia congenita also had varying degrees of hidradenitis suppurativa. We suggest an association between this type of pachyonychia congenita and hidradenitis suppurativa.     

Pachyonychia congenita associated with median rhomboid glossitis

A 3-year-old girl presented with subungual hyperkeratosis and nail plates with increased transverse curvature, distal elevation, yellow-brown discoloration, and mild thickening. The changes, which affected all 20 nails, had developed during the first year of life. Mucocutaneous examination showed the presence of median rhomboid glossitis. The patient's mother had similar nail changes, which had been present since infancy as well as a focal plantar keratoderma and hyperhidrosis. The patient's clinical presentation and history were compatible with a diagnosis of pachyonychia congenita, a rare heritable disease that affects the nails, skin, oral and laryngeal mucosae, teeth, and hair. Dominant-negative mutations in four keratin genes (K6a, K6b, K16, and K17) lead to keratinocyte fragility and the resultant pachyonychia congenita phenotype. Successful targeted therapies are currently lacking for this oftentimes disabling disorder. Although oral manifestations are a common feature of PC, to our knowledge, this represents the first report of median rhomboid glossitis in association with PC.     

Report of the 13th Annual International Pachyonychia Congenita Consortium Symposium

The International Pachyonychia Congenita Consortium (IPCC) is a group of physicians and scientists from around the world dedicated to developing therapies for pachyonychia congenita, a rare autosomal dominant skin disorder. The research presented at the 13th Annual Research Symposium of the IPCC, held on 10–11 May 2016, in Scottsdale, AZ, U.S.A., is reported here.     

Pachyonychia congenita Typ II (Jackson-Lawler-Syndrom)

Pachyonychia congenita (PC) is a rare ectodermal dysplasia with variable expression. The condition is usually inherited as an autosomal dominant trait. Several classifications of PC have been proposed. Feinstein and colleagues suggested four clinical types of PC. Type II, the Jackson-Lawler-Syndrome, is characterized by multiple epidermal cysts, palmoplantar bullae and hyperhidrosis as well as natal teeth in addition to the main findings of pachyonychia, palmoplantar hyperkeratosis and follicular keratosis. We report two patients (father and son) with Jackson-Lawler-Syndrome and describe in detail pathogenesis, diagnostic criteria and treatment approaches as well as the different classifications of pachyonychia congenita.     

Keratin 17 expression in the hard epithelial context of the hair and nail, and its relevance for the pachyonychia congenita phenotype

The hard-keratin-containing portion of the murine hair shaft displays a positive immunoreactivity with an antibody against the soft epithelial keratin, K17. The K17-expressing cell population is located in the medulla compartment of the hair. Consistent with this observation, K17-containing cells also occur in the presumptive medulla precursor cells located in the hair follicle matrix. Western blot analysis of hair extracts prepared from a number of mouse strains confirms this observation and suggests that K17 expression in the hair shaft is a general trait in this species. The expression of K17 in human hair extracts is restricted to eyebrow and facial hair samples. These are the major sites for the occurrence of the pili torti (twisted hair) phenotype in the type 2 (Jackson-Lawler) form of pachyonychia congenita, previously shown to arise from inherited K17 mutations. Given that all forms of pachyonychia congenita show an involvement of the nail, we compared the expression of the two other genes mutated in pachyonychia congenita diseases, K6 and K16, with that of K17 in human nail. All three keratins are abundantly expressed within the nail bed epithelium, whereas K17 protein is expressed in the nail matrix, which contains the epithelial cell precursors for the nail plate. Our data suggest a role for K17 in the formation and maintenance of various skin appendages and directly support the concept that pachyonychia congenita is a disease of the nail bed.     

A systematic review of reported cases of pachyonychia congenita tarda

Pachyonychia congenita (PC) describes a group of genodermatoses manifesting as thickened nails, palmoplantar keratoderma (PPK) and increased risk of cutaneous infections. PC tarda (PCT) describes late‐onset PC, and associated genetic polymorphisms have been identified. There has been discussion that PCT may not be a distinct entity but rather misdiagnosed ectodermal dysplasia (ED) or PPK. Clarification of this is important for appropriate diagnosis, management and patient and genetic counselling. We aimed to conduct a systematic review of all reported cases of PCT in the published literature and collate evidence of genetic polymorphisms and clinical features to compare with known features of PC, ED and PPK. PubMed (1946 to 1 July 2018), Scopus (1955 to 1 July 2018) and Web of Science (1990 to 1 July 2018) databases were searched for case reports of PCT with no search restrictions on date or language. The search strategy included the terms pachyonychia congenita tarda OR pachyonychia congenita AND (late onset OR delayed OR PCT). In total, 13 reports describing 19 individual cases of PCT were identified. Of the three identified genetic polymorphisms, the earliest identified has been shown to be highly probably pathogenic, with the second likely to result in a benign amino acid change, while the third has since been shown to be nonpathogenic,. No epigenetic studies have been performed on any reported cases. Previous authors have suggested that a number of cases of PCT may be misdiagnosed ED or PPK. The findings of our review cannot refute this suggestion, and highlight the need for thorough clinical documentation of suspected cases of PCT and thorough genetic screening of kindred to identify causative genetic polymorphisms. Further high‐quality datasets and reporting are needed to give further insight into the nature of PCT as a unique entity.     

Treatment of pachyonychia congenita

There are currently no specific treatments for pachyonychia congenita (PC). Available treatments generally are directed at specific manifestations of the disorder, and an effective treatment plan must recognize that different patients are more or less troubled by different manifestations of the disease. Treatment for all aspects of PC has been less than completely satisfactory. Very few studies have compared different approaches to treatment, and fewer still have given longitudinal follow-up of efficacy and patient acceptance. This review is essentially a compilation of anecdotes. It was collected from physicians' reports in the literature, from direct communication with physicians currently following patients with PC and from patients who answered a questionnaire on the Pachyonychia Congenita Project web page (http://www.pachyonychia.org/Registry.html).     

Nail manifestations of some important genetic disorders in children

There are some genetic disorders in which nail changes are the major feature, such as the nail patella syndrome and pachyonychia congenita. Nail abnormalities are a constant feature of other disorders such as hidrotic ectodermal dysplasia, dyskeratosis congenita, some forms of epidermolysis bullosa, and ichthyosis follicularis with alopecia and photophobia. Nail changes often occur in mal de Meleda, Papillon–Lefèvre syndrome, and the keratitis-ichthyosis-deafness (KID) syndrome and are an occasional feature in some other ichthyoses and in incontinentia pigmenti. In Goltz syndrome, nail changes can be supportive of the diagnosis in a case in which the other features are minimal or subtle. In Darier disease, nail changes may be the first sign of the disorder and lead to the diagnosis being made. Nail changes may occur in some conditions such as Apert syndrome and Adams–Oliver syndrome as a result of abnormalities of the distal phalanges.     

Novel keratin 17 mutations in pachyonychia congenita type 2

Pachyonychia congenita type 2 is an inherited ectodermal dysplasia characterized by hypertrophic nail dystrophy and multiple pilosebaceous cysts. Focal nonepidermolytic palmoplantar keratoderma, natal teeth, and pili torti may also be present. Epithelial tissues affected in pachyonychia congenita type 2 express the keratin pair K6b/K17. Here, we report three novel heterozygous mutations in the K17 gene (KRT17A) in patients presenting with pachyonychia congenita type 2. These mutations, R94-98del (deletion of the peptide sequence RLASY) and missense mutations R94P and L95Q, are all within the 1A domain hotspot for pathogenic keratin mutations.     

Eruptive vellus hair cyst in a patient with pachyonychia congenita.

Pachyonychia congenita is characterized by symmetrical nail dystrophy, palmoplantar keratoderma, oral leukokeratosis, and follicular hyperkeratosis. In addition to these features, multiple cutaneous cysts of various kinds have been described. We report a case of pachyonychia congenita associated with eruptive vellus hair cyst.