Expression of the sarco/endoplasmic reticulum calcium ATPase type 2 and 3 isoforms in normal skin and Darier's disease

BACKGROUND

Darier's disease (DD) is caused by mutations in ATP2A2, which encodes the sarco/endoplasmic reticulum calcium ATPase type 2 (SERCA2), a member of a family of calcium pumps important in intracellular calcium signalling. SERCA2 has two isoforms. SERCA2a occurs mainly in cardiac and skeletal muscle, whereas SERCA2b occurs ubiquitously and is coexpressed with the related SERCA type 3 (SERCA3) in many tissues. It is not known why mutations in the widely expressed SERCA2 manifest as a focal skin disease.

OBJECTIVES

To provide insight into the pathogenesis of DD by examining SERCA isoform expression in normal skin and DD skin.

METHODS

Using immunohistochemistry we studied SERCA2a, SERCA2b and SERCA3 expression in nonlesional and lesional skin from seven patients with DD and normal skin from seven control subjects. We quantified SERCA2a and SERCA2b staining intensity by grey scale analysis of fluorescence intensity.

RESULTS

In normal and DD epidermis both SERCA2a and SERCA2b staining was seen. SERCA2a staining in epidermis was less intense relative to pilar muscle whereas SERCA2b staining in epidermis was of marginally greater intensity than in pilar muscle. SERCA3 was not expressed in normal or DD epidermis, but was found in eccrine glands and blood vessels. No reduction was detected in SERCA2a or SERCA2b staining intensity in DD nonlesional epidermis compared with control epidermis. In within-patient comparisons, SERCA2a and SERCA2b staining in lesional epidermis was less intense than in nonlesional epidermis.

CONCLUSIONS

Both SERCA2a and SERCA2b are present in epidermis, although the latter may predominate. The absence of coexpressed SERCA3 in epidermis may explain the localization of DD. Comparable SERCA2 staining intensity in nonlesional DD and control epidermis, even in patients predicted to be haploinsufficient, suggests partial compensation by upregulation of the normal allele. Unknown additional factors may trigger focal lesions by overcoming this compensation. Reduced staining intensity in lesional tissue may be secondary, or may reflect local downregulation of SERCA2 expression predisposing to development of focal lesions.

Cross-linked envelopes in nail plate in lamellar ichthyosis

BACKGROUND

Corneocytes of the nail plate, like those of the stratum corneum, generate cornified envelopes (CEs) of cross-linked protein that can be visualized readily after removal of non-cross-linked protein by detergent extraction. Defective CE formation occurs in epidermal scale and hair in transglutaminase 1 (TGM1)-negative lamellar ichthyosis (LI) and has been proposed as a diagnostic aid for this syndrome.

OBJECTIVES

(i) To ascertain whether TGM1 is important for CE formation in nail; (ii) to characterize CE abnormalities occurring in LI that may be distinguished from other types of inherited ichthyosis when nail samples are subjected to detergent extraction; and (iii) to evaluate the utility of nails as a diagnostic aid for LI.

METHODS

Nail samples were provided by nine patients previously classified as having TGM1-negative LI, four with other types of ichthyotic conditions and six normal controls. Samples were extracted extensively in sodium dodecyl sulphate under reducing conditions and examined by light and electron microscopy.

RESULTS

After extraction, defective CE cross-linking was visualized in epidermal corneocytes from seven of nine patients exhibiting TGM1-negative LI, whereas nail samples from patients with the other syndromes were normal. The defects in CE structure resembled those recently reported for LI scale, although in some cases residual CE and CE-associated structures were present.

CONCLUSIONS

Despite the paucity of clinical nail symptoms in LI, TGM1 activity is important for generation of normal CE in nail plate, consistent with its importance in protein cross-linking in interfollicular epidermis and hair. Lack of this activity leads to a strikingly aberrant appearance of CE in LI nail after detergent extraction that is evident ultrastructurally in a large majority of cases. Nail envelopes therefore could provide a useful diagnostic tool in distinguishing LI from other ichthyoses with overlapping clinical features.

Post-menopausal frontal fibrosing alopecia

Post-menopausal frontal fibrosing alopecia (PFFA) has become an increasingly recognized distinct clinical entity in recent years. Most cases have been reported from Australia; however, it seems likely that the condition is under-recognized. PFFA has similarities to lichen planopilaris but is differentiated by a distinctive symmetrical fronto-temporal distribution and progressive course. We report two cases from the UK and review the literature.

Genes, growth factors and acanthosis nigricans

Acanthosis nigricans (AN) occurs most commonly in association with hyperinsulinaemia and more rarely as a paraneoplastic syndrome. It is also a feature of several genetic disorders. Indirect evidence suggests a role for tyrosine kinase growth factor receptor signalling in the pathogenesis of AN. Defects in the insulin receptor gene causing insulin resistance and AN are well recognized, but recent data in several other syndromes of this association, including lipodystrophic disorders, have identified causative defects in other pathways. The mechanism of AN due to insulin resistance is most probably direct or indirect activation of the insulin-like growth factor 1 receptor by high levels of circulating insulin. However, more direct evidence for abnormal tyrosine kinase receptor signalling in AN has been provided by studies of craniosynostosis and skeletal dysplasia syndromes with AN, which have identified activating mutations in fibroblast growth factor receptors.

Safety and efficacy of combined high-dose treatment with calcipotriol ointment and solution in patients with psoriasis

BACKGROUND

In the vast majority of psoriatic patients, psoriatic lesions are localised on the body as well as on the scalp. Therefore, safety data on the combined use of calcipotriol in lotion and calcipotriol in ointment are needed.

OBJECTIVE

This study investigated the effect of high-dose treatment with a combination of calcipotriol ointment and scalp solution on calcium metabolism, indices of bone turnover and PASI in patients with extensive psoriasis.

METHODS

Following a 2-week wash-out period, 88 patients were randomised to 4 weeks of treatment with either calcipotriol ointment/scalp solution (80-100 g/week and 30-50 ml/week, respectively; n = 41) or with a dithranol/tar regimen (n = 47). Patients were seen at weeks 1, 2 and 4 during treatment and 1 week following cessation of treatment.

RESULTS

No significant differences at the end of treatment were found between the 2 groups with respect to 24-hour urinary excretion of calcium (expressed as calcium/creatinine ratio), phosphate or pyridinoline, serum concentrations of calcium (albumin corrected), creatinine, phosphate, parathyroid hormone, 25-hydroxyvitamin D(3), 1,25-dihydroxyvitamin D(3), osteocalcin, alkaline phosphatase (total and bone-specific iso-enzymes) or 1-collagen telopeptide. At the end of treatment, the psoriasis area and severity index had decreased by 57.4% in the calcipotriol group and by 36.1% in the dithranol/tar group (p = 0.004). Investigators' and patients' assessments of overall efficacy also favoured treatment with calcipotriol (p < 0.001).

CONCLUSION

The combined use of calcipotriol ointment/scalp solution did not affect the indices of calcium metabolism or bone turnover and was significantly more effective than dithranol/tar in reducing disease severity and extent in patients with extensive psoriasis.

Genetic epidemiology of Darier's disease: a population study in the west of Scotland

BACKGROUND

Darier's disease has a world-wide distribution, but estimates of prevalence have varied. The discovery that the disease is due to mutations in ATP2A2 provides the opportunity to study the genetic epidemiology of the disease in localized populations.

OBJECTIVES

To survey the prevalence of Darier's disease in the west of Scotland and look for founder effects in this population.

METHODS

We ascertained cases of Darier's disease in the west of Scotland and used genealogy and mutational analysis to seek common ancestry.

RESULTS

Seventy-eight current cases were identified, giving a prevalence of approximately 1 : 30 000. While 63 cases gave a history of Darier's disease in previous generations, conventional genealogy identified only two pairs of two family groups with common ancestry within the last 180 years. Eleven patients (14%; three of whom had in total four affected children) had probable de novo mutations. Causative mutations in ATP2A2 have been identified in 11 of 15 pedigrees screened for mutation, but no two share the same mutation.

CONCLUSIONS

High estimates of prevalence are likely to be due to intensive ascertainment, rather than founder effects. Darier's disease is likely to be more common than has been recognized in other populations.

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.

Platelet and cardiac function in Darier's disease

ATP2A2, the gene that is abnormal in Darier's disease, encodes SERCA2, a calcium pump that is expressed in many tissues. The wide expression of SERCA2 might suggest that ATP2A2 mutations would cause a multisystem disease. There is however, no evidence of consistent extracutaneous manifestations of Darier's disease. We have conducted preliminary studies in patients with Darier's disease, in two extracutaneous systems in which SERCA2 is known to be important, in order to investigate whether subtle defects have been overlooked. We found no evidence for altered cardiac function in 10 patients using two-dimensional, colour and Doppler echocardiography. There were no consistent defects in platelet function in 12 patients, using bleeding time and aggregation studies. We conclude that the skin is sensitive to defects in SERCA2 function to which other systems appear robust.

The clinical photography of Herbert Brown: a perspective on early 20th Century dermatology

Herbert Brown was Consultant Dermatologist to the Victoria Infirmary, Glasgow during the first half of the 20th Century. He was a keen amateur photographer, and his large archive of photographs illustrates comprehensively the work of a clinical dermatologist in that era.

trans-dominant inhibition of connexin-43 by mutant connexin-26: implications for dominant connexin disorders affecting epidermal differentiation

Dominant mutations of GJB2-encoding connexin-26 (Cx26) have pleiotropic effects, causing either hearing impairment (HI) alone or in association with palmoplantar keratoderma (PPK/HI). We examined a British family with the latter phenotype and identified a new dominant GJB2 mutation predicted to eliminate the amino acid residue E42 (ΔE42) in Cx26. To dissect the pathomechanisms that result in diverse phenotypes of dominant GJB2 mutations, we studied the effect of three Cx26 mutants (ΔE42, D66H and R75W) identified in individuals with PPK/HI, and another (W44C) present in individuals with non-syndromic HI on gap junctional intercellular communication. We expressed mutant Cx26 alone and together with the epidermal connexins Cx26, Cx37 and Cx43 in paired Xenopus oocytes, and measured the intercellular coupling by dual voltage clamping. Homotypic expression of each connexin as well as co-expression of wild-type (wt) Cx26/wtCx43 and wtCx26/wtCx37 yielded variable, yet robust, levels of channel activity. However, all four Cx26 mutants were functionally impaired and failed to induce intercellular coupling. When co-expressed with wtCx26, all four mutants suppressed the wtCx26 channel activity consistent with a dominant inhibitory effect. However, only those Cx26 mutants associated with a skin phenotype also significantly (P&lt;0.05) inhibited intercellular conductance of co-expressed wtCx43, indicating a direct interaction of mutant Cx26 units with wtCx43. These results demonstrate, for the first time, a trans-dominant negative effect of Cx26 mutants in vitro. Furthermore, they support a novel concept suggesting that the principal mechanism for manifestation of dominant GJB2 mutations in the skin is their dominant interference with the function of wtCx43. This assumption is further corroborated by our finding that Cx26 and Cx43 focally colocalize at gap junctional plaques in affected skin tissue of two carriers of ΔE42.

Localization of a gene (MCUL1) for multiple cutaneous leiomyomata and uterine fibroids to chromosome 1q42.3-q43

Dominant transmission of multiple uterine and cutaneous smooth-muscle tumors is seen in the disorder multiple leiomyomatosis (ML). We undertook a genomewide screen of 11 families segregating ML and found evidence for linkage to chromosome 1q42.3-q43 (maximum multipoint LOD score 5.40). Haplotype construction and analysis of recombinations permitted the minimal interval containing the locus, which we have designated "MCUL1," to be refined to an approximately 14-cM region flanked by markers D1S517 and D1S2842. Allelic-loss studies of tumors indicated that MCUL1 may act as a tumor suppressor. Identification of MCUL1 should have wide interest, since this gene may harbor low-penetrance variants predisposing to the common form of uterine fibroids and/or may undergo somatic mutation in sporadic leiomyomata.

A novel mutation in the keratin 13 gene causing oral white sponge nevus

White sponge nevus (WSN) is an autosomal-dominantly inherited form of mucosal leukokeratosis. Defects in keratins, proteins that form the stress-bearing cytoskeleton in epithelia, have been shown to cause several epithelial fragility disorders. Recently, mutations in the genes encoding mucosal-specific keratins K4 and K13 were shown to be the underlying cause of WSN. We have studied a large Scottish family with 19 persons affected by WSN in four generations. The K4 locus was excluded by genetic linkage analysis; however, genetic linkage consistent with a K13 defect was obtained. Subsequently, a heterozygous missense mutation 335A>G was detected in exon 1 of the KRT13 gene, predicting the amino acid change N112S in the 1A domain of the K13 polypeptide. The mutation was confirmed in affected family members and was excluded from 50 unaffected people by restriction enzyme analysis. These results confirm that mucosal keratin defects are the cause of WSN.

Mutant loricrin is not crosslinked into the cornified cell envelope but is translocated into the nucleus in loricrin keratoderma

Loricrin is a major constituent of the epidermal cornified cell envelope. We have recently identified heterozygous loricrin gene mutations in two dominantly inherited skin diseases, the ichthyotic variant of Vohwinkel syndrome and progressive symmetric erythrokeratoderma, collectively termed loricrin keratoderma. In order to see whether the mutant loricrin molecules predicted by DNA sequencing are expressed in vivo and to define their pathologic effects, we raised antibodies against synthetic peptides corresponding to the mutated sequences of loricrin. Immunoblotting of horny cell extracts from loricrin keratoderma patients showed specific bands for mutant loricrin. Immunohistochemistry of loricrin keratoderma skin biopsies showed positive immunoreactivity to the mutant loricrin antibodies in the nuclei of differentiated epidermal keratinocytes. The immunostaining was localized to the nucleoli of the lower granular cell layer. As keratinocyte differentiation progressed the immunoreactivity moved gradually into the nucleoplasm leaving nucleoli mostly nonimmunoreactive. No substantial staining was observed along the cornified cell envelope. This study confirmed that mutant loricrin was expressed in the loricrin keratoderma skin. Mutant loricrin, as a dominant negative disrupter, is not likely to affect cornified cell envelope crosslinking directly, but seems to interfere with nuclear/nucleolar functions of differentiating keratinocytes. In addition, detection of the mutant loricrin in scraped horny layer could provide a simple noninvasive screening test for loricrin keratoderma. J Invest Dermatol 115:1088-1094 2000

Connexin mutations associated with palmoplantar keratoderma and profound deafness in a single family

Recently, mutations in two gap junction genes, GJB2 and GJB3 (encoding Connexin 26 and Connexin 31, respectively), have been shown to underlie either inherited hearing loss and skin disease or both disorders. In this study, we have extended our analysis of a small family in which palmoplantar keratoderma and various forms of deafness is segregating. In addition to the previously described sequence variant M34T in GJB2, two other sequence variants were identified: D66H also in GJB2 and R32W in GJB3. As D66H segregated with the skin disease, it is likely to underlie the palmoplantar keratoderma. The other two gap junction variants identified may contribute to the type of hearing impairment and the variable severity of the skin disease in the family.

Hailey-Hailey disease is caused by mutations in ATP2C1 encoding a novel Ca(2+) pump

Hailey-Hailey disease (HHD) is an autosomal dominant skin disorder characterized by suprabasal cell separation (acantholysis) of the epidermis. Previous genetic linkage studies localized the gene to a 5 cM interval on human chromosome 3q21. After reducing the disease critical region to <1 cM, we used a positional cloning strategy to identify the gene ATP2C1, which is mutated in HHD. ATP2C1 encodes a new class of P-type Ca(2+)-transport ATPase, which is the homologue for the rat SPLA and the yeast PMR1 medial Golgi Ca(2+)pumps and is related to the sarco(endo)plasmic calcium ATPase (SERCA) and plasma membrane calcium ATPase (PCMA) families of Ca(2+)pumps. The predicted protein has the same apparent transmembrane organization and contains all of the conserved domains present in other P-type ATPases. ATP2C1 produces two alternative splice variants of approximately 4.5 kb encoding predicted proteins of 903 and 923 amino acids. We identified 13 different mutations, including nonsense, frameshift insertion and deletions, splice-site mutations, and non-conservative missense mutations. This study demonstrates that defects in ATP2C1 cause HHD and together with the recent identification of ATP2A2 as the defective gene in Darier's disease, provide further evidence of the critical role of Ca(2+)signaling in maintaining epidermal integrity.

Connexin mutations associated with palmoplantar keratoderma and profound deafness in a single family

Recently, mutations in two gap junction genes, GJB2 and GJB3 (encoding Connexin 26 and Connexin 31, respectively), have been shown to underlie either inherited hearing loss and skin disease or both disorders. In this study, we have extended our analysis of a small family in which palmoplantar keratoderma and various forms of deafness is segregating. In addition to the previously described sequence variant M34T in GJB2, two other sequence variants were identified: D66H also in GJB2 and R32W in GJB3. As D66H segregated with the skin disease, it is likely to underlie the palmoplantar keratoderma. The other two gap junction variants identified may contribute to the type of hearing impairment and the variable severity of the skin disease in the family.

Novel proline substitution mutations in keratin 16 in two cases of pachyonychia congenita type 1

Pachyonychia congenita (PC) is a group of inherited ectodermal dysplasias, the characteristic phenotype being hypertrophic nail dystrophy. Two main clinical subtypes, PC-1 and PC-2, are inherited as autosomal dominant disorders, but other less well characterized clinical forms also exist. The PC-1 phenotype may be distinguished by the absence of the epidermal cysts found in PC-2, and it has been shown to be caused by mutations in either keratin K16 or its expression partner, the K6a isoform of K6. Mutations in K16 have also been shown to cause a milder related phenotype, focal non-epidermolytic palmoplantar keratoderma. Recently, we have developed a long-range polymerase chain reaction (PCR) strategy which allows specific amplification of the entire functional K16 gene (KRT16A), without amplification of the two K16 pseudogenes (psiKRT16B and psiKRT16C), enabling mutation analysis based on genomic DNA. Here, using this methodology, we describe novel mutations R127P and Q122P in the helix 1A domain of K16 in two families presenting with PC-1. Both mutations were excluded from 50 normal unrelated individuals by restriction enzyme analysis of K16 PCR fragments. In one family, ultrastructural analysis was performed, revealing distinctive tonofilament abnormalities. Specifically, keratin filament bundles were greatly condensed, but did not form the dense amorphous aggregates seen in a number of other keratin disorders. In the second kindred, autosomal dominant cataract was present in some but not all members affected by PC. As the cataract phenotype did not fully cosegregate with the K16 mutation, and given that K16 is not expressed in the lens, these two phenotypes may be coincidental.

Identification of novel mutations in basic hair keratins hHb1 and hHb6 in monilethrix: implications for protein structure and clinical phenotype

Monilethrix is an hereditary hair dystrophy recently shown to be due to mutations in the helix termination motif of two type II (basic) human hair keratin genes, hHb1 and hHb6. It has been suggested that mutation in hHb1 produces a less severe phenotype. We have studied hair keratin genes and clinical features in 18 unrelated pedigrees of monilethrix from Germany, Scotland, Northern Ireland, and Portugal, in 13 of which mutations have not previously been identified. By examining the rod domains of hHb1, hHb3 and hHb6, we have identified mutations in nine of the new pedigrees. We again found the glutamine-lysine substitution (E413K) in the helix termination motif of hHb6 in two families, and in another, the corresponding E413K substitution in the hHb1 gene. In four families a similar substitution E402K was present in a nearby residue. In addition two novel mutations within the helix initiation motif of hHb6 were found in Scottish and Portuguese cases, in whom the same highly conserved asparagine residue N114 was mutated to histidine (N114H) or aspartic acid (N114D) residues, respectively. In four other monilethrix pedigrees mutations in these domains of hHb1, hHb3, and hHb6 were not found. The mutations identified predict a variety of possible structural consequences for the keratin molecule. A comparison of clinical features and severity between cases with hHb1 and hHb6 mutations does not suggest distinct effects on phenotype, with the possible exception of nail dystrophy, commoner with hHb1 defects. Other factors are required to explain the marked variation in clinical severity within and between cases.

ATP2A2 mutations in Darier's disease: variant cutaneous phenotypes are associated with missense mutations, but neuropsychiatric features are independent of mutation class

Darier's disease (DD) is an autosomal dominant skin disorder characterized clinically by multiple keratotic papules, and histologically by focal loss of adhesion between epidermal cells (acantholysis) and by abnormal keratinization. Variant forms of cutaneous phenotype, sometimes familial, have been described. Associated neuropsychiatric features, including mental handicap, schizophrenia, bipolar disorder and epilepsy, have also been reported. The cause of DD was shown recently to be mutation in the ATP2A2 gene at 12q24.1, which encodes the sarco-endoplasmic reticulum calcium ATPase type 2 (SERCA2). Here, we show that while both common isoforms of SERCA2 are expressed in the cytoplasm of cultured keratinocytes and fibroblasts, in adult skin sections only the longer isoform, SERCA2b, was expressed abundantly in epidermal structures. Extended mutation analysis in European DD patients using single-strand conformation polymorphism and/or direct sequencing identified 40 different patient-specific mutations in 47 families. The majority (23/40) were likely to result in nonsense-mediated RNA decay. The remaining 17 were missense mutations distributed throughout the protein and were associated significantly with atypical clinical features. The clearest association was with the familial haemorrhagic variant where all four families tested had a missense mutation. Three of the families (one Scottish family and two unrelated Italian families) exhibited the same N767S substitution in the M5 transmembrane domain, and a fourth family, from Sweden, had a C268F substitution in the M3 transmembrane domain. Neuropsychiatric features did not appear to be associated with a specific class of mutation and may be an intrinsic, but inconsistent, effect of defective ATP2A2 expression.

The gene for hypotrichosis of Marie Unna maps between D8S258 and D8S298: exclusion of the hr gene by cDNA and genomic sequencing

Hypotrichosis of Marie Unna (MU) is an autosomal dominant hair-loss disorder with onset in childhood. A genomewide search for the gene was performed in a large Dutch family using 400 fluorescent microsatellite markers. Linkage was detected with marker D8S258, and analysis of this family and a further British kindred with additional markers in the region gave a combined maximum two-point LOD score of 13.42, with D8S560. Informative recombinants placed the MU gene in a 2.4-cM interval between markers D8S258 and D8S298. Recently, recessive mutations in the hr gene were reported in families with congenital atrichia, and this gene was previously mapped close to the MU interval. By radiation-hybrid mapping, we placed the hr gene close to D8S298 but were unable to exclude it from the MU interval. This, with the existence of the semidominant murine hr allele, prompted us to perform mutation analysis for this gene. Full-length sequencing of hr cDNA obtained from an affected individual showed no mutations. Similarly, screening of all exons of the hr gene amplified from the genomic DNA of an affected individual revealed no mutations. Analysis of expressed sequences and positional cloning of the MU locus is underway.

A missense mutation in connexin26, D66H, causes mutilating keratoderma with sensorineural deafness (Vohwinkel's syndrome) in three unrelated families

The multiplicity of functions served by intercellular gap junctions is reflected by the variety of phenotypes caused by mutations in the connexins of which they are composed. Mutations in the connexin26 (Cx26) gene ( GJB2 ) at 13q11-q13 are a major cause of autosomal recessive hearing loss (DFNB1), but have also been reported in autosomal dominant deafness (DFNA3). We now report a Cx26 mutation in three families with mutilating keratoderma and deafness [Vohwinkel's syndrome (VS; MIM 124500), as originally described]. VS is characterized by papular and honeycomb keratoderma associated with constrictions of digits leading to autoamputation, distinctive starfish-like acral keratoses and moderate degrees of deafness. In a large British pedigree, we have mapped the defect to the Cx26 locus. All 10 affected members were heterozygous for a non-conservative mutation, D66H, in Cx26. The same mutation was found subsequently in affected individuals from two unrelated Spanish and Italian pedigrees segregating VS, suggesting that D66H in Cx26 is a common mutation in classical VS. This mutation occurs at a highly conserved residue in the first extracellular domain of the Cx26 molecule, and may exert its effects by interfering with assembly into connexons, docking with adjacent cells or gating properties of the gap junction. Our results provide evidence that a specific mutation in Cx26 can impair epidermal differentiation, as well as inner ear function.

Mutations in ATP2A2, encoding a Ca2+ pump, cause Darier disease

Darier disease (DD) is an autosomal-dominant skin disorder characterized by loss of adhesion between epidermal cells (acantholysis) and abnormal keratinization. Recently we constructed a 2.4-Mb, P1-derived artificial chromosome contig spanning the DD candidate region on chromosome 12q23-24.1. After screening several genes that mapped to this region, we identified mutations in the ATP2A2 gene, which encodes the sarco/endoplasmic reticulum Ca2(+)-ATPase type 2 isoform (SERCA2) and is highly expressed in keratinocytes. Thirteen mutations were identified, including frameshift deletions, in-frame deletions or insertions, splice-site mutations and non-conservative missense mutations in functional domains. Our results demonstrate that mutations in ATP2A2 cause DD and disclose a role for this pump in a Ca(2+)-signalling pathway regulating cell-to-cell adhesion and differentiation of the epidermis.

The value of in-patient dermatology: a survey of in-patients in Scotland and Northern England

Dermatology in-patient units are frequently threatened with reduction or closure, yet there are few objective data regarding the nature and use of in-patient management with which to assess their value. We have surveyed 300 patients admitted during March 1997 to dermatology units throughout Scotland and Northern England, to establish their clinical and social profile, and the outcome of admission. All departments provided phototherapy and out-patient treatment services, and 84% of those admitted lived within an hour's travel of one of these. Three diagnostic groups (psoriasis, eczema and leg ulcers) accounted for 83% of in-patient days. Patients were admitted principally because of disease severity but many, including half of those with psoriasis, had concurrent medical problems such as alcohol abuse, psychiatric disorder or arthropathy. Many patients with psoriasis and leg ulcers were from socially deprived areas, as defined by low Carstairs index scores, and a similar proportion received income support. Eighteen per cent of patients, mainly those with acute disorders, would have needed admission irrespective of dermatology bed availability. Out-patient management was considered the next best alternative for only 28% of patients, and many patients would have been expected to treat themselves. By contrast, 84% of patients admitted were cleared or substantially improved, or had procedures completed as planned, and another 12% were partially improved. Outcomes were particularly good in psoriasis, eczema and infection groups. We have demonstrated that in-patient management is highly effective in providing remission in chronic skin disease, and our survey also suggests that concomitant disability or social factors mean that for many such patients ambulatory care cannot replace this service.

Epidermolytic palmoplantar keratoderma due to a novel type of keratin mutation, a 3-bp insertion in the keratin 9 helix termination motif

Epidermolytic palmoplantar keratoderma (EPPK) is an autosomal dominant genodermatosis characterized by diffuse keratoderma, typically with an erythematous border. Histologically, palmoplantar epidermis shows suprabasal cytolysis and ultrastructurally, tonofilament aggregation with overlying epidermolytic hyperkeratosis. Mutations in the KRT9 gene, encoding keratin 9 (K9), a cytoskeletal protein expressed exclusively in suprabasal keratinocytes of palmoplantar epidermis, have been reported to cause EPPK. To date, all KRT9 defects reported in EPPK have been missense mutations in exon 1, which encodes the start of the alpha-helical rod domain. However, based on studies of other keratin disorders, it was postulated that mutations at the other end of the rod domain might also produce the EPPK phenotype. Here, we report the first mutation in the 2B domain of KRT9, 1362ins3, leading to an insertion of histidine in the helix termination motif of the K9 polypeptide. Insertional mutations have not been previously described in keratins. The phenotype of this case is similar to EPPK caused by 1A domain mutations, demonstrating that mutations in either of the helix boundary motif sequences of K9 are detrimental to keratin function and keratinocyte structure.

Mutations in keratin K9 in kindreds with epidermolytic palmoplantar keratoderma and epidemiology in Northern Ireland

Epidermolytic palmoplantar keratoderma (EPPK, MIM #144200) is an autosomal dominant disorder in which hyperkeratosis confined to the palms and soles is characterized histologically by cytolysis of suprabasal keratinocytes. Mutations in the keratin 9 gene (KRT9), a type 1 keratin expressed exclusively in the suprabasal keratinocytes of palmoplantar epidermis, have previously been demonstrated in this disorder. Here, we have studied four Northern Irish kindreds presenting with EPPK. By direct sequencing of polymerase chain reaction products, heterozygous missense mutations in exon 1 of KRT9 were detected in all the families. These included a novel mutation M156T; as well as M156V in two kindreds; and R162Q in the remaining family. All mutations were confirmed by reverse strand sequencing and restriction enzyme analysis. The point prevalence of EPPK in Northern Ireland was found to be 4.4 per 100,000. To date, all reported EPPK mutations occur in the helix initiation motif at the start of the central coiled-coil rod domain of K9.

A mutational hotspot in the 2B domain of human hair basic keratin 6 (hHb6) in monilethrix patients

Monilethrix is an inherited hair dystrophy in which affected, fragile, hairs have an unique beaded morphology. Ultrastructural studies suggest a defect in filament structure in the cortex of the hair, and the hard keratins of hair and nail are thus candidate genes. In several families with autosomal dominant monilethrix, the disorder has been linked to the type II keratin gene cluster at chromosome 12q13. Recently, causative mutations in the critical helix termination motif in the 2B domain of the human hair basic keratin 6 (hHb6) have been identified. We now report the results of sequencing this domain in 13 unrelated families or cases with monilethrix. Five of the 13 had the same mutation as previously found, a G to A transversion leading to a lysine for glutamic acid substitution (E413K) in the 2B domain (residue 117 of the 2B helix) of hHb6. The mutation was confirmed by a restriction fragment length polymorphism assay developed for this purpose, and, as this mutation is evidently a common cause of the syndrome, for use in screening other cases. In eight families or cases, however, including three in whom linkage data are consistent with a defect at the type II keratin locus, no mutation was found in this domain of hHb6.

Keratin 17 mutations cause either steatocystoma multiplex or pachyonychia congenita type 2

Pachyonychia congenita type 2 (PC-2; Jackson-Lawler syndrome) is an autosomal dominant disorder characterized by hypertrophic nail dystrophy, mild focal keratoderma, multiple pilosebaceous cysts and other features of ectodermal dysplasia. Keratin 17 (K17) is a differentiation-specific keratin expressed in the nail bed, hair follicle, sebaceous gland and other epidermal appendages. Previously, we have demonstrated that PC-2 is caused by mutations in K17 and that similar mutations in this gene can present as steatocystoma multiplex with little or no nail dystrophy. Here, we describe three unrelated kindreds carrying K17 mutations. Two of these families have identical missense mutations (R94C) in the 1A domain of K17. However, while affected members of one kindred have the classical features of PC-2, affected persons in the other family have the steatocystoma multiplex phenotype. In a third family with PC-2, mutation N92S was detected, bringing the total number of distinct mutations reported in K17 thus far to 11. These results demonstrate that K17 mutations commonly underlie both PC-2 and steatocystoma multiplex and that the alternate phenotypes which arise from these genetic lesions in K17 are independent of the specific mutation involved.

Refined genetic mapping of the darier locus to a <1-cM region of chromosome 12q24.1, and construction of a complete, high-resolution P1 artificial chromosome/bacterial artificial chromosome contig of the critical region

Darier disease (DD) (MIM 124200) is an autosomal dominant skin disorder characterized by loss of adhesion between epidermal cells and by abnormal keratinization. We present linkage analysis showing, in four families, key recombination events that refine the location of the DD locus on chromosome 12q23-24.1 to a region of <1 cM. We have constructed a YAC/P1 artificial chromosome (PAC)/bacterial artificial chromosome (BAC)-based physical map that encompasses this refined DD region. The map consists of 35 YAC, 69 PAC, 16 BAC, and 2 cosmid clones that were ordered by mapping 54 anonymous sequence-tagged sites. The critical region is estimated to be 2.4 Mb in size, with an average marker resolution of 37.5 kb. The refinement of the critical interval excludes the ALDH2, RPL6, PTPN11, and OAS genes, as well as seven expressed sequence tags (ESTs) previously mapped in the DD region. The three known genes (ATP2A2, PPP1CC, and SCA2) and the 10 ESTs mapped within the critical region are not obvious candidates for the DD gene. Therefore, this detailed integrated physical, genetic, and partial transcript map provides an important resource for the isolation of the DD gene and, possibly, other disease genes.

Loricrin mutation in Vohwinkel's keratoderma is unique to the variant with ichthyosis

A mutation in the glycine-rich cornified envelope protein loricrin has recently been reported in Vohwinkel's keratoderma (honeycomb keratoderma with pseudoainhum), in a pedigree amongst whom ichthyosis was also a feature. We have studied two further families with Vohwinkel's keratoderma for evidence ofloricrin mutations. Our first family (VK1) also had ichthyosis but not deafness. In lesional and nonlesional skin, granular and transitional cell layers were increased. In immunoelectron-microscopic studies cornified envelopes were abnormally thin and were labeled densely by anti-involucrin antibodies, but only sparsely by antiloricrin antibodies; however, abnormal intranuclear granules seen in granular and cornified layer cells were labeled by antibodies to both C- and N-terminal loricrin. Microsatellite markers in VK1 supported linkage to the loricrin locus in the epidermal differentiation complex at 1q21 (Zmax = 2.48). The loricrin gene was sequenced, identifying a heterozygous mutation as previously reported: a G insertion producing a frameshift after codon 231 and an abnormal C-terminal peptide lacking residues necessary for cross-linking. In our second family (VK2), affected members had sensorineural deafness but not ichthyosis. Immunoelectron-microscopic studies showed normal loricrin distribution, and assuming complete penetrance, linkage to 1q21 was excluded. Vohwinkel's keratoderma is thus clinically and genetically heterogeneous. Only the variant with ichthyosis appears to be due to loricrin mutation. As the arginine-rich domain in C-terminal loricrin caused by the frameshift contains several potential bipartite nuclear localization signals, we suggest that the intranuclear accumulation of loricrin in VK1 is due to these motifs, and may be unique to insertional mutation.

Treatment of psoriasis with intermittent short course cyclosporin (Neoral). A multicentre study

A 1 year, prospective multicentre study was performed to investigate the efficacy and safety of intermittent treatment with cyclosporin in psoriasis vulgaris. Subjects received cyclosporin (Neoral) 5 mg/kg per day until achieving 90% reduction in area affected, or for a maximum of 12 weeks. Those failing to demonstrate a satisfactory response were withdrawn. When further treatment was required, cyclosporin was recommenced. This cycle was repeated up to three times. Psoriasis activity was recorded using the area affected and sign scores for erythema, scaling and infiltration. Overall assessments of response and tolerability were recorded. Forty-one subjects, mean age 36, mean PASI 12.8, entered the first treatment period. Thirty-three received a second period of treatment and 16 a third. Eighteen failed to complete the study as planned: five were withdrawn due to adverse events, four due to treatment failure and nine due to protocol violations. At the end of each treatment period, significant improvements were seen in all efficacy parameters. Overall response was graded as 'considerable improvement' or 'minimal or no symptoms', by over 80% of subjects and investigators. Median intervals to relapse for subjects remaining in the study were 72 days (range 28-329) and 53 days (range 14-141) after periods 1 and 2, respectively. There were significant increases in mean serum creatinine and blood pressure during each treatment period. However, there were no significant differences in either parameter between baseline and the final follow-up visit. At the end of each treatment period, overall tolerability of the treatment was considered 'good' or 'very good' by over 80% of subjects and investigators.

Systemic lupus erythematosus complicating complement type 2 deficiency: successful treatment with fresh frozen plasma

We report a man who presented in 1981 at the age of 30 with cutaneous lupus erythematosus (LE), which was resistant to a range of treatments over the subsequent 11 years. In 1991 he suffered fits, dysphasia and agitated depression, and in 1992 a severe septicaemic illness. Systemic LE was diagnosed, and investigation showed homozygous complement type 2 deficiency (C2d). Over a period of 30 months he has received 6 weekly fresh frozen plasma. Since starting this treatment his cutaneous disease has resolved and his depression, verbal fluency and psychomotor scores improved. We have not observed any adverse effects to this treatment and suggest it should be considered in similar patients.

Missense mutations in keratin 17 cause either pachyonychia congenita type 2 or a phenotype resembling steatocystoma multiplex

Pachyonychia congenita (PC) is a group of autosomal dominant ectodermal dysplasias in which the main phenotypic characteristic is hypertrophic nail dystrophy. In the Jackson-Lawler form (PC-2), pachyonychia is accompanied by multiple pilosebaceous cysts, natal teeth, and hair abnormalities. By direct sequencing of genomic PCR products, we report heterozygous K17 missense mutations in the same conserved protein motif in a further five PC-2 families (K17 N92S in one familial and three sporadic cases; K17 Y98D in one familial case) confirming that mutations in this gene are a common cause of PC-2. We also show heterozygous missense mutations in K17 (N92H and R94H) in two families diagnosed as steatocystoma multiplex. Mild nail defects were observed in some but not all of these patients on clinical re-evaluation of these families. All the K17 mutations reported here were shown to co-segregate with the disease in the pedigrees analyzed and were excluded from 100 unaffected, unrelated chromosomes by restriction enzyme analysis of K17 genomic PCR products. We conclude that phenotypic variation is observed with K17 mutations, as is the case with other keratin disorders.

A mutation in the mucosal keratin K4 is associated with oral white sponge nevus

White sponge nevus (WSN) is a benign autosomal dominant disorder which affects non-cornifying stratified squamous epithelia (MIM 193900) (ref. 1). Phenotypically it presents as white 'spongy' plaques (oral leukokeratoses), most commonly in the mouth but also reported in the esophagus and anogenital mucosa. Histologically, the plaques show evidence of hyperproliferation, acanthosis and tonofilament aggregation. These types of pathogenic changes are characteristic of many of the epidermal keratin disorders. Keratins are expressed in pairs by epithelial cells in a tissue and cell specific manner. The major differentiation specific keratins of the buccal mucosa, nasal, esophageal and anogenital epithelia are K4 and K13 (ref. 7). The tissue distribution and nature of the lesions in patients affected by WSN suggested that mutations in K4 and/or K13 might be responsible for this disorder. We have now confirmed this hypothesis and report here a three base-pair (bp) deletion in the helix initiation peptide of K4 in affected members from two families with this condition.

A gene for monilethrix is closely linked to the type II keratin gene cluster at 12q13

Monilethrix is an uncommon hereditary disorder of hair and nail which produces hair fragility and a variable alopecia. Many of the dystrophic hairs have a unique beaded morphology. Ultrastructural changes suggest a defect in the microfilament structure of the cortex of the hair shaft,and hence the cysteine-rich trichocyte keratins are candidate genes. Here, in two families with autosomal dominant monilethrix, we have excluded linkage to the type I keratin gene cluster on chromosome 17q, but show that the disorder is closely linked to the type II keratin cluster on 12q, where genes for basic trichocyte keratins are found. The combined maximum lod score for D12S96 was 12.27 at theta=0.0. This is the first mapping of a primary human hair disorder and the first evidence implicating a defect of the word 'hard' keratins of hair and nail disease.

Remission of ordinary psoriasis following a short clearance course of cyclosporin

We set out to show that the assumption is incorrect that continuous treatment with cyclosporin is necessary in psoriasis, as this tenet forms a basis for current recommended treatment regimens. Sixty patients with mild to moderate plaque psoriasis were allocated at random to treatment with oral cyclosporin 5 mg/kg/day (30 patients) or topical dithranol and ultraviolet B therapy (30 patients) for up to 16 weeks until clear (median time 6 weeks cyclosporin and 8 dithranol), and the times to relapse compared. The patients were seen monthly for up to 8 months, and the severity and the extent of psoriasis were assessed. Relapse, defined as return of psoriasis to 50% of the area at the start of the trial or patient demand for further treatment, was not significantly different between the groups (hazard ratio 1.11, 95% CI 0.55-2.32). No patients suffered a rebound of severe disease and none relapsed in the first 8 weeks after stopping treatment. The relapse rate was higher following cyclosporin from 8 to 28 weeks after treatment and following dithranol from 28 to 34 weeks. The patients with arthritis had a higher median joint severity score at relapse than prior to treatment with cyclosporin. At the end of 8 months, 5 patients treated with dithranol and 8 patients with cyclosporin remained clear, 75% and 67% having relapsed. We conclude that rapid relapse does not occur after clearance of mild to moderate plaque psoriasis with cyclosporin and the relapse rate was no different from dithranol treatment.

Linkage analyses in British pedigrees suggest a single locus for Darier disease and narrow the location to the interval between D12S105 and D12S129

Darier disease is a dominantly inherited skin disorder in which there appears to be abnormal adhesion between keratinocytes. We and others have shown that the disease in some British pedigrees is closely linked to markers mapping to 12q23-q24.1. In the present study we have defined crossovers that enable us to narrow the location of the disease gene to the interval between the D12S105 and the D12S129 markers. This interval may be expected to be on the order of about 4 cM on the basis of linkage data obtained using the primary CEPH reference families. Our data provide further evidence for locus homogeneity: each of four large British pedigrees, two of which have previously been subjected to preliminary characterization, shows statistically significant evidence for linkage to markers mapping to 12q23-q24.1.