Identification of a locus for type I punctate palmoplantar keratoderma on chromosome 15q22-q24

Is punctate palmoplantar keratoderma type 1 associated with malignancy? A systematic review of the literature

BACKGROUND

An association between punctate palmoplantar keratoderma type 1 (PPPK1) and malignancy has been proposed for decades. Some authors suggest that individuals with PPPK1 should undergo screening for various types of malignancies while others caution that an association is not well-established. In this systematic review, we summarized and evaluated the current evidence for a possible association between PPPK1 and malignancy.

METHODS

The review was conducted along PRISMA guidelines. The search used Embase, MEDLINE, Scopus, and the Human Gene Mutation Database up to March 2022. All studies reporting on individuals with the diagnosis of PPPK1 with or without history of malignancy were included. Two authors screened for eligible studies, extracted predefined data, and performed a quality assessment.

RESULTS

Of 773 studies identified, 45 were included. Most studies were reports on single families (24 of 45 studies) or multiple families (10 of 45 studies). The number of index cases with PPPK1 across all included studies was 280, and when family members reported with PPPK1 were added, a total of 817 individuals were identified. Overall, 23 studies reported on individuals with PPPK1 with a history of malignancy, whereas 22 studies reported on individuals with PPPK1 without a history of malignancy. Although the extracted data were not considered to be of sufficient quality to synthesize and answer our research question, the review did not confirm an association between PPPK1 and malignancy.

CONCLUSION

This review shows that there is a lack of well-designed studies on this topic to conclude whether individuals with PPPK1 have an increased risk of malignancy. Based on the present literature, however, we could not confirm an association between PPPK1 and malignancy and find it highly questionable if patients with PPPK1 should be offered surveillance for malignancies.

Hereditary Palmoplantar Keratoderma: A Practical Approach to the Diagnosis

The ridged skin of the palms and soles has several unique features: (i) presence of dermatoglyphics created by alternating ridges and grooves forming a unique pattern, (ii) presence of the highest density of eccrine sweat glands and absence of pilosebaceous units, and (iii) differential expression of keratins compared to the glabrous skin. These features explain the preferential localization of palmoplantar keratoderma (PPK) and several of its characteristic clinical features. PPK develops as a compensatory hyperproliferation of the epidermis and excessive production of stratum corneum in response to altered cornification of the palmoplantar skin due to mutations in the genes encoding several of the proteins involved in it. PPK can manifest as diffuse, focal, striate, or punctate forms per se or as a feature of several dermatological or systemic diseases. There is a wide genetic and phenotypic heterogeneity in hereditary PPK, due to which reaching an accurate diagnosis only on the basis of clinical features may be sometimes challenging for the clinicians in the absence of molecular studies. Nevertheless, recognizing the clinical patterns of keratoderma, extent of involvement, degree of mutilation, and associated appendageal and systemic involvement may help in delineating different forms. Molecular studies, despite high cost, are imperative for accurate classification, recognizing clinical patterns in resource poor settings is important for appropriate diagnosis, genetic counseling, and management. This review intends to develop a practical approach for clinical diagnosis of different types of hereditary PPK with reasonable accuracy.

Haploinsufficiency for AAGAB causes clinically heterogeneous forms of punctate palmoplantar keratoderma

Palmoplantar keratodermas (PPKs) are a group of disorders that are diagnostically and therapeutically problematic in dermatogenetics. Punctate PPKs are characterized by circumscribed hyperkeratotic lesions on the palms and soles with considerable heterogeneity. In 18 families with autosomal dominant punctate PPK, we report heterozygous loss-of-function mutations in AAGAB, encoding α- and γ-adaptin-binding protein p34, located at a previously linked locus at 15q22. α- and γ-adaptin-binding protein p34, a cytosolic protein with a Rab-like GTPase domain, was shown to bind both clathrin adaptor protein complexes, indicating a role in membrane trafficking. Ultrastructurally, lesional epidermis showed abnormalities in intracellular vesicle biology. Immunohistochemistry showed hyperproliferation within the punctate lesions. Knockdown of AAGAB in keratinocytes led to increased cell division, which was linked to greatly elevated epidermal growth factor receptor (EGFR) protein expression and tyrosine phosphorylation. We hypothesize that p34 deficiency may impair endocytic recycling of growth factor receptors such as EGFR, leading to increased signaling and cellular proliferation.

Nonsense mutations in AAGAB cause punctate palmoplantar keratoderma type Buschke-Fischer-Brauer

Punctate palmoplantar keratodermas (PPKPs) are rare autosomal-dominant inherited skin diseases that are characterized by multiple hyperkeratotic plaques distributed on the palms and soles. To date, two different loci in chromosomal regions 15q22-15q24 and 8q24.13-8q24.21 have been reported. Pathogenic mutations, however, have yet to be identified. In order to elucidate the genetic cause of PPKP type Buschke-Fischer-Brauer (PPKP1), we performed exome sequencing in five affected individuals from three families, and we identified in chromosomal region 15q22.33-q23 two heterozygous nonsense mutations-c.370C>T (p.Arg124(∗)) and c.481C>T (p.Arg161(∗))-in AAGAB in all affected individuals. Using immunoblot analysis, we showed that both mutations result in premature termination of translation and truncated protein products. Analyses of mRNA of affected individuals revealed that the disease allele is either not detectable or only detectable at low levels. To assess the consequences of the mutations in skin, we performed immunofluorescence analyses. Notably, the amount of granular staining in the keratinocytes of affected individuals was lower in the cytoplasm but higher around the nucleus than it was in the keratinocytes of control individuals. AAGAB encodes the alpha-and gamma-adaptin-binding protein p34 and might play a role in membrane traffic as a chaperone. The identification of mutations, along with the results from additional studies, defines the genetic basis of PPKP1 and provides evidence that AAGAB plays an important role in skin integrity.

Type I punctate palmoplantar keratoderma (Buschke-Fisher-Brauer disease) in a family--a report of two cases

BACKGROUND

Inherited palmoplantar keratoderma are a rare group of disorder affecting the palm and sole characterised by hyperkeratosis resulting in severe disability and deformities.

OBJECTIVE

To report a rare case of punctate palmoplantar keratoderma.

METHOD

A case attending our OPD is reported.

RESULT

Case report.

CONCLUSION

This case is reported for its unique presentation and rarity.

[Case report: squamous cell carcinoma, radial forearm flap and Huriez syndrome. Focus on a rare pathology]

Huriez disease is a rare autosomal dominant pathology characterized by the triad hypoplastic nail, hyperkeratosis and scleroatrophy of distal extremities. One of its most principal complications is the development of an aggressive squamous cell carcinoma. We present a case of a 62-year old patient who had an acute two hands scleroatrophy associated with recurrent squamous cell carcinoma treated by large excision and covered by trophic and thick radial forearm flap. This flap allowed us to treat the wound and the sclerosis shrinkage with aim to give back the functional benefit to the patient. It also gave the patient an oncological treatment despite aggressive management in one step surgery. Furthermore, one year later we did not observe cutaneous flap histological modification that could have degenerated into cancer. A multidisciplinary approach with dermatologists, geneticists and plastic surgeons is essential in addition with close medical supervision because of high cancer risks.

[Clinical and genetic characteristics of Buschke-Fischer-Brauer's disease in a Tunisian family]

BACKGROUND

Punctate palmoplantar keratoderma (PPPK), or Buschke-Fischer-Brauer's disease, is a rare form of genodermatosis with autosomal dominant transmission and with variable penetrance. Its molecular basis remains unknown. Two loci were found to be linked to this disease: one on 15q22 and the other on 8q24. We report the clinical and genetic characteristics of PPPK in a Tunisian family.

PATIENTS AND METHODS

A Tunisian family with PPPK was identified through a proband. As far as possible, history taking, physical examination, histopathological tests and blood sampling for DNA extraction were carried out for each patient.

RESULTS

Seventeen patients were included in this study. Age ranged from 15 to 81 years with a sex-ratio of 3.2 m/f. Lesions appeared between the ages of 10 and 65 years and at a mean of 28 years. Clinically, lesions ranged from few keratotic papules on the palms to coalescence of lesions in plaques over palmar and/or plantar surfaces. Hyperhydrosis, hypopigmented macules and nail dystrophy were frequently associated. In all patients, histopathological examination revealed thickening of the epidermis with compact orthohyperkeratosis overlying a small and sharply demarcated area of depressed epidermis. Mechanical measures and keratolytic ointments proved non-beneficial. Genotyping for chromosomes 8 and 15 as well as LOD scores confirmed genetic linkage with the suspected locus on chromosome 15q, with the interval of the locus in question reduced to 3.26 Mb. This region is flanked by markers D15S987 and D15S153.

CONCLUSION

Our study of this family confirmed the classical characteristics of KPP-BFB as well as demonstrating several associated clinical signs of which the significance will be determined in subsequent studies. Further screening studies to identify mutated genes in the region of interest will help us to understand the molecular basis of this disease and hopefully to propose suitable treatment.

Factors affecting statistical power in the detection of genetic association

The mapping of disease genes to specific loci has received a great deal of attention in the last decade, and many advances in therapeutics have resulted. Here we review family-based and population-based methods for association analysis. We define the factors that determine statistical power and show how study design and analysis should be designed to maximize the probability of localizing disease genes.

Refined localization of a punctate palmoplantar keratoderma gene to a 5.06-cM region at 15q22.2-15q22.31

BACKGROUND

Punctate palmoplantar keratoderma (PPK) is a rare autosomal dominant cutaneous disorder characterized by numerous hyperkeratotic papules distributed on the palms and soles. Two loci for punctate PPK were recently found to be located on 8q24.13-8q24.21 and 15q22-15q24. However, no genes for this disease have been identified to date. Objectives To refine the previously mapped regions and to identify the disease gene locus in a four-generation Chinese family with punctate PPK.

METHODS

Genetic linkage analysis was carried out in this family using microsatellite markers on chromosomes 8q and 15q. Two-point linkage analysis was performed using Linkage programs version 5.10 and the haplotype was constructed using Cyrillic version 2.02 software.

RESULTS

We failed to confirm our previous locus at 8q24.13-8q24.21, but significant evidence for linkage was observed in the region of 15q with a maximum two-point LOD score of 5.38 at D15S153 (theta = 0.00). Haplotype analysis localized the punctate PPK locus within the region defined by D15S651 and D15S988. This region overlaps by 5.06 cM with the previously reported punctate PPK region.

CONCLUSIONS

This study refines a disease gene causing punctate PPK to a 5.06-cM interval at 15q22.2-15q22.31.