Abstract:Summary
Palmoplantar keratodermas comprise a diverse group of acquired and hereditary disorders marked by excessive thickening of the epidermis of palms and soles. Early onset and positive family history suggest a genetic cause. While hereditary forms of palmoplantar keratoderma (PPK) may represent the sole or dominant clinical feature, they may also be associated with other ectodermal defects or extracutaneous manifestations. In recent years, much progress has been made in deciphering the genetic basis of PPK… Show more
“…Acquired PPKs are commonly caused by inflammatory dermatoses, such as psoriasis, eczema and chronic hand dermatitis, but can also be associated with systemic or infectious diseases, induced by chemicals or drugs, or be a sign of internal malignancy . Hereditary PPKs comprise an increasing number of entities with different prognoses, and a multitude of associated cutaneous and extracutaneous features . To date, the diagnosis of the different hereditary PPKs is based mainly on inheritance pattern, age at onset, morphology, distribution and severity of hyperkeratosis, pattern of additional dermatologic and systemic manifestations, and histopathological findings.…”
The term palmoplantar keratoderma (PPK) indicates any form of persistent thickening of the epidermis of palms and soles and includes genetic as well as acquired conditions. We review the nosology of hereditary PPKs that comprise an increasing number of entities with different prognoses, and a multitude of associated cutaneous and extracutaneous features. On the basis of the phenotypic consequences of the underlying genetic defect, hereditary PPKs may be divided into the following: (i) non-syndromic, isolated PPKs, which are characterized by a unique or predominant palmoplantar involvement; (ii) non-syndromic PPKs with additional distinctive cutaneous and adnexal manifestations, here named complex PPKs; (iii) syndromic PPKs, in which PPK is associated with specific extracutaneous manifestations. To date, the diagnosis of the different hereditary PPKs is based mainly on clinical history and features combined with histopathological findings. In recent years, the exponentially increasing use of next-generation sequencing technologies has led to the identification of several novel disease genes, and thus substantially contributed to elucidate the molecular basis of such a heterogeneous group of disorders. Here, we focus on hereditary non-syndromic isolated and complex PPKs. Syndromic PPKs are reviewed in the second part of this 2-part article, where other well-defined genetic diseases, which may present PPK among their phenotypic manifestations, are also listed and diagnostic and therapeutic approaches for PPKs are summarized.
“…Acquired PPKs are commonly caused by inflammatory dermatoses, such as psoriasis, eczema and chronic hand dermatitis, but can also be associated with systemic or infectious diseases, induced by chemicals or drugs, or be a sign of internal malignancy . Hereditary PPKs comprise an increasing number of entities with different prognoses, and a multitude of associated cutaneous and extracutaneous features . To date, the diagnosis of the different hereditary PPKs is based mainly on inheritance pattern, age at onset, morphology, distribution and severity of hyperkeratosis, pattern of additional dermatologic and systemic manifestations, and histopathological findings.…”
The term palmoplantar keratoderma (PPK) indicates any form of persistent thickening of the epidermis of palms and soles and includes genetic as well as acquired conditions. We review the nosology of hereditary PPKs that comprise an increasing number of entities with different prognoses, and a multitude of associated cutaneous and extracutaneous features. On the basis of the phenotypic consequences of the underlying genetic defect, hereditary PPKs may be divided into the following: (i) non-syndromic, isolated PPKs, which are characterized by a unique or predominant palmoplantar involvement; (ii) non-syndromic PPKs with additional distinctive cutaneous and adnexal manifestations, here named complex PPKs; (iii) syndromic PPKs, in which PPK is associated with specific extracutaneous manifestations. To date, the diagnosis of the different hereditary PPKs is based mainly on clinical history and features combined with histopathological findings. In recent years, the exponentially increasing use of next-generation sequencing technologies has led to the identification of several novel disease genes, and thus substantially contributed to elucidate the molecular basis of such a heterogeneous group of disorders. Here, we focus on hereditary non-syndromic isolated and complex PPKs. Syndromic PPKs are reviewed in the second part of this 2-part article, where other well-defined genetic diseases, which may present PPK among their phenotypic manifestations, are also listed and diagnostic and therapeutic approaches for PPKs are summarized.
“…The inheritance pattern, phenotype characteristics, and location of the hyperkeratosis as well as the presence of additional extracutaneous features form the basis of classification of different types of PPK (Has and Technau-Hafsi, 2016, Lucker et al., 1994, Schiller et al., 2014). Mutations in more than 20 genes have been associated with both isolated and syndromic forms of hereditary PPK.…”
In this paper, we report three patients with severe palmoplantar keratoderma associated with ichthyosis and sensorineural deafness. Biallelic mutations were found in VPS33B, encoding VPS33B, a Sec1/Munc18 family protein that interacts with Rab11a and Rab25 proteins and is involved in trafficking of the collagen-modifying enzyme LH3. Two patients were homozygous for the missense variant p.Gly131Glu, whereas one patient was compound heterozygous for p.Gly131Glu and the splice site mutation c.240-1G>C, previously reported in patients with arthrogryposis renal dysfunction and cholestasis syndrome. We demonstrated the pathogenicity of variant p.Gly131Glu by assessing the interactions of the mutant VPS33B construct and its ability to traffic LH3. Compared with wild-type VPS33B, the p.Gly131Glu mutant VPS33B had reduced coimmunoprecipitation and colocalization with Rab11a and Rab25 and did not rescue LH3 trafficking. Confirming the cell-based experiments, we found deficient LH3-specific collagen lysine modifications in patients’ urine and skin fibroblasts. Additionally, the epidermal ultrastructure of the p.Gly131Glu patients mirrored defects in tamoxifen-inducible VPS33B-deficient Vps33bfl/fl-ERT2 mice. Both patients and murine models revealed an impaired epidermal structure, ascribed to aberrant secretion of lamellar bodies, which are essential for epidermal barrier formation. Our results demonstrate that p.Gly131Glu mutant VPS33B causes an autosomal recessive keratoderma-ichthyosis-deafness syndrome.
“…Systemic retinoids, in particular acitretin, may induce improvement in palmoplantar hyperkeratosis, although they are not recommended in epidermolytic PPK, due to a possible worsening of disease manifestations . Importantly, in women of childbearing age pregnancy must be excluded and contraception initiated before starting retinoid therapy .…”
Hereditary palmoplantar keratodermas (PPKs) comprise a large and heterogeneous group of disorders characterized by persistent thickening of the epidermis at palmar and plantar surfaces. Clinical and genetic features of isolated and complex PPKs have been reviewed in part I of this 2-part review. Here we focus on clinical and molecular classification of syndromic PPKs which are recognized by additional extracutaneous manifestations, in particular deafness, specific mucosal lesions, cardiomyopathy, inborn errors of metabolism, involvement of internal organs or disorders of sexual development. Other genetic diseases, which may show palmoplantar involvement, such as selected subtypes of hereditary epidermolysis bullosa, various hereditary ichthyoses and other keratinization disorders, several ectodermal dysplasias and some multisystem genetic disorders, are also briefly summarized. PPK diagnosis is based on inheritance pattern, age at onset, morphology, distribution and severity of hyperkeratosis, pattern of additional dermatological and systemic manifestations and laboratory findings. Molecular analysis is at present the gold standard to confirm the diagnosis in PPK forms due to mutations in known causative genes. No specific and curative therapy is currently available for PPKs which highly impair patients' quality of life. Topical treatments are symptomatic and offer only temporary relief. Among systemic treatments, retinoids improve disease symptoms in the majority of patients.
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