Arch Dermatol Res. 2012 Jan 19;
Dahlqvist J, Westermark GT, Vahlquist A, Dahl N

Autosomal recessive congenital ichthyosis (ARCI) is a group of disorders characterized by abnormal desquamation of the skin and a disrupted epidermal water barrier. Ichthyin/NIPAL4 gene mutations have been identified in a subgroup of ARCI patients, but the role of ichthyin in epidermis remains elusive. In order to obtain new insights concerning the characteristics of ichthyin and the ARCI pathogenesis, we studied the expression and localization of ichthyin and related epidermal components in cultured keratinocytes and skin sections from patients with Ichthyin mutations and healthy controls. We observed an up-regulation of Ichthyin mRNA levels after in vitro differentiation of keratinocytes from both a patient with Ichthyin mutations and controls. Confocal and electron microscopy analyses of immunolabeled skin sections revealed that ichthyin localizes to desmosomes and keratins in both patients with mutant Ichthyin and controls, with an increased immunolabeling in patients. Nile red lipid analysis of skin sections exposed intra-cellular lipid accumulations in cells of the granular and cornified layers in patients but not in controls, consistent with the pathognomonic lipid membrane structures previously identified in epidermis from patients. Our combined findings indicate that ichthyin is associated with keratins and desmosomes in epidermis and is involved in lipid metabolism, possibly through processing of lamellar bodies. These results provide new clues to the understanding of the epidermal water barrier and the pathogenesis in ARCI.

J Dermatol Sci. 2011 Dec 24;
Nakagawa N, Yamamoto M, Imai Y, Sakaguchi Y, Takizawa T, Ohta N, Yagi N, Hatta I, Hitomi K, Takizawa T, Takeda J, Tsuda T, Matsuki M, Yamanishi K

BACKGROUND: Mutations in the gene encoding transglutaminase 1 (TG1) are responsible for various types of autosomal recessive congenital ichthyosis (ARCI), such as lamellar ichthyosis (LI), congenital ichthyosiform erythroderma (CIE) and some minor variants of ARCI. A point mutation of R143C in the β-sandwich domain of TG1 has been often identified in patients with LI or CIE. OBJECTIVE: To elucidate the effect of that point mutation on skin barrier structures and functions, we generated mice with a point mutation of R142C, which corresponds to the R143C mutation in human TG1. METHODS: A mouse line with the R142C point mutation in TG1 was established using a gene targeting technique and the Cre-loxP system. The skin phenotypes were analyzed in homozygous mutant Tgm1(R142C/R142C) mice. RESULTS: In the skin of Tgm1(R142C/R142C) mice, expression of the mutant transcripts was comparable with wild-type or Tgm1(+/R142C) mice. However, the amount of mutated protein in the skin was markedly decreased in Tgm1(R142C/R142C) mice, and the TG1 activity of Tgm1(R142C/R142C) keratinocytes was almost lost. Tgm1(R142C/R142C) mice exhibited morphological and functional skin barrier defects and neonatal lethality. The stratum corneum of those mice lacked cornified envelopes, and loricrin, the major structural component, failed to assemble at the corneocyte cell periphery. Tgm1(R142C/R142C) mice showed a marked increase in transepidermal water loss and their skin was easily permeable to toluidine blue dye. The intercellular lipid lamellar structures of the stratum corneum were irregular and the 13-nm periodic X-ray diffractions from the stratum corneum lipid molecules were lost in vivo. CONCLUSION: From these results, we suggest that the R142C mutation of TG1 reduces the enzyme stability which is indispensable for development of the stratum corneum and skin barrier function and for postnatal survival of mice.

Eur J Dermatol. 2012 Jan 17;
Nawaz S, Tariq M, Ahmad I, Malik NA, Baig SM, Dahl N, Klar J

A Mutations in the gene encoding the ABCA12 protein are associated with different subtypes of autosomal recessive congenital ichthyosis (ARCI), including Harlequin ichthyosis (HI), lamellar ichthyosis (LI) and non-bullous congenital ichthyosiform erythroderma (NCIE). Disruption of ABCA12 lead to perturbed lipid transport in lamellar granules and a defective intercellular lipid layer of the stratum corneum. We have identified a large consanguineous Pakistani family affected by NCIE. Autozygosity mapping showed that affected individuals are homozygous for the ABCA12 gene region. Subsequent mutation screening revealed a homozygous c.4676G>T transition in all five affected family members. The mutation results in a novel p.G1559V substitution within the first nucleotide binding domain of ABCA12. The combined results support that an ABCA12 missense mutation, despite its location in a functional domain, may be associated with a mild ichthyosis phenotype. Furthermore, our findings increase the mutational spectrum in ABCA12 associated with ARCI of diagnostic and prognostic importance.

Nat Genet. 2012; 44(2): 140-7
Grall A, Guaguère E, Planchais S, Grond S, Bourrat E, Hausser I, Hitte C, Le Gallo M, Derbois C, Kim GJ, Lagoutte L, Degorce-Rubiales F, Radner FP, Thomas A, Küry S, Bensignor E, Fontaine J, Pin D, Zimmermann R, Zechner R, Lathrop M, Galibert F, André C, Fischer J

Ichthyoses comprise a heterogeneous group of genodermatoses characterized by abnormal desquamation over the whole body, for which the genetic causes of several human forms remain unknown. We used a spontaneous dog model in the golden retriever breed, which is affected by a lamellar ichthyosis resembling human autosomal recessive congenital ichthyoses (ARCI), to carry out a genome-wide association study. We identified a homozygous insertion-deletion (indel) mutation in PNPLA1 that leads to a premature stop codon in all affected golden retriever dogs. We subsequently found one missense and one nonsense mutation in the catalytic domain of human PNPLA1 in six individuals with ARCI from two families. Further experiments highlighted the importance of PNPLA1 in the formation of the epidermal lipid barrier. This study identifies a new gene involved in human ichthyoses and provides insights into the localization and function of this yet uncharacterized member of the PNPLA protein family.

J Dermatol. 2011 Nov 21;
Alavi A, Shahshahani MM, Klotzle B, Fan JB, Ronaghi M, Elahi E

Ichthyosis is a heterogeneous disorder characterized by abnormal skin scaling over the whole body. Autosomal recessive congenital ichthyosis (ARCI) comprises various forms, the most important of which are lamellar ichthyosis (LI) and congenital ichthyosiform erythroderma (CIE). Seven genes have been identified to be causative of ARCI, and these account for disease in 60-80% of the patients. There is notable phenotypic overlap between the major forms of ARCI, and a strong genotype-phenotype correlation has not been found. Here, we initially aimed to identify the causative gene in a large Iranian ARCI pedigree, and subsequently performed genetic analysis on four other affected pedigrees. A genotype-phenotype correlation was sought. Whole genome homozygosity mapping using high-density single nucleotide polymorphism chips was performed on the large pedigree. Linkage to chromosome 5 and a mutation in NIPAL4 causing p.G297R were identified. The same mutation was also identified in two of the remaining four Iranian pedigrees. Two of the NIPAL4 mutation bearing pedigrees were classified as CIE and one as LI. Notably, all NIPAL4 mutation-bearing patients manifested diffuse yellowish keratoderma on the palms and soles. We provide evidence suggesting presentation of this diffuse yellowish keratoderma may be indicative of mutations in NIPAL4, providing an easily assessable genotype-phenotype correlation.

J Am Acad Dermatol. 2011 Oct 13;
Hernández-Martín A, Garcia-Doval I, Aranegui B, de Unamuno P, Rodríguez-Pazos L, González-Enseñat MA, Vicente A, Martín-Santiago A, Garcia-Bravo B, Feito M, Baselga E, Círia S, de Lucas R, Ginarte M, González-Sarmiento R, Torrelo A

BACKGROUND: Previous reports on the prevalence of autosomal recessive congenital ichthyosis (ARCI) were based on single source data, such as lists of members in a patient association. These sources are likely to be incomplete. OBJECTIVES: We sought to describe the prevalence of ARCI. METHODS: We obtained data from 3 incomplete sources (dermatology departments, a genetic testing laboratory, and the Spanish ichthyosis association) and combined them using the capture-recapture method. RESULTS: We identified 144 living patients with ARCI. Of these, 62.5% had classic lamellar ichthyosis and 30.6% had congenital ichthyosiform erythroderma. The age distribution included fewer elderly patients than expected. The prevalence of ARCI in patients younger than 10 years, the best estimate as less subject to bias, was 16.2 cases per million inhabitants (95% confidence interval 13.3-23.0). According to the capture-recapture model, 71% of the patients were not being followed up in reference units, 92% did not have a genetic diagnosis, and 78% were not members of the ichthyosis association. LIMITATIONS: The prevalence of ARCI in Spain and findings related to the Spanish health care system might not be generalizable to other countries. CONCLUSIONS: The prevalence of ARCI is higher than previously reported. Many patients are not being followed up in reference units, do not have a genetic diagnosis, and are not members of a patient association, indicating room for improvement in their care. Data suggesting a reduced number of older patients might imply a shorter life expectancy and this requires further study.

Hip Int. 2011 Jul-Aug; 21(4): 487-9
Beazley JC, Ho K, Ilchyshyn A, Foguet P

Harlequin ichthyosis (HI) is a rare autosomal recessive skin disorder. No orthopaedic procedure has previously been described on a patient with HI. We report the case of a 17-year-old patient with HI who presented with bilateral juvenile idiopathic arthritis of the hips who underwent bilateral total hip replacements. Our standard operative and postoperative regime was followed and no complications occurred. One year after the second procedure our patient had a Oxford hip score of 43 and was very satisfied with the result.

Dis Model Mech. 2011 Nov; 4(6): 777-85
Li Q, Frank M, Akiyama M, Shimizu H, Ho SY, Thisse C, Thisse B, Sprecher E, Uitto J

Zebrafish (Danio rerio) can serve as a model system to study heritable skin diseases. The skin is rapidly developed during the first 5-6 days of embryonic growth, accompanied by expression of skin-specific genes. Transmission electron microscopy (TEM) of wild-type zebrafish at day 5 reveals a two-cell-layer epidermis separated from the underlying collagenous stroma by a basement membrane with fully developed hemidesmosomes. Scanning electron microscopy (SEM) reveals an ordered surface contour of keratinocytes with discrete microridges. To gain insight into epidermal morphogenesis, we have employed morpholino-mediated knockdown of the abca12 and snap29 genes, which are crucial for secretion of lipids and intracellular trafficking of lamellar granules, respectively. Morpholinos, when placed on exon-intron junctions, were >90% effective in preventing the corresponding gene expression when injected into one- to four-cell-stage embryos. By day 3, TEM of abca12 morphants showed accumulation of lipid-containing electron-dense lamellar granules, whereas snap29 morphants showed the presence of apparently empty vesicles in the epidermis. Evaluation of epidermal morphogenesis by SEM revealed similar perturbations in both cases in the microridge architecture and the development of spicule-like protrusions on the surface of keratinocytes. These morphological findings are akin to epidermal changes in harlequin ichthyosis and CEDNIK syndrome, autosomal recessive keratinization disorders due to mutations in the ABCA12 and SNAP29 genes, respectively. The results indicate that interference of independent pathways involving lipid transport in the epidermis can result in phenotypically similar perturbations in epidermal morphogenesis, and that these fish mutants can serve as a model to study the pathomechanisms of these keratinization disorders.

J Coll Physicians Surg Pak. 2011 Aug; 21(8): 503-5
Habib A, Pasha W, Raza N, Hameed A

Harlequin ichthyosis is a rare and extremely severe form of congenital ichthyosis. The affected neonates usually do not survive beyond first few days after birth, but several long-term survivals have been noted. The inheritance is thought to be autosomal recessive. It has recently been shown that the vast majority of affected individuals are homozygous for mutations in the ABCA12 gene, which cause a deficiency of the epidermal lipid transporter and result in hyperkeratosis and abnormal barrier function. Prenatal diagnosis is possible. We report a case of a newborn with Harlequin ichthyosis, a product of consanguineous marriage, with a history of similar disease leading to early neonatal death previously in a sibling.

Ann Trop Paediatr. 2011; 31(3): 247-9
Rossi G, Mesia D

Harlequin ichthyosis (HI) is a very rare severe form of autosomal recessive congenital ichthyosis, usually associated with stillbirth and early neonatal death. A newborn girl with HI is described. She presented in a critical condition with severe universalis hyperkeratosis, diffuse scales and deep erythematous fissures. She received preventive systemic antibiotics and hygienic nursing with skin and eye care, feeding and appropriate hydration. She was discharged at 28 days in good general condition.

Dermatoendocrinol. 2011 Apr; 3(2): 107-12
Akiyama M

ABCA12 is a member of the large superfamily of ATP-binding cassette (ABC) transporters, which bind and hydrolyze ATP to transport various molecules across limiting membranes or into vesicles. The ABCA subfamily members are thought to be lipid transporters. ABCA12 is a keratinocyte transmembrane lipid transporter protein associated with the transport of lipids in lamellar granules to the apical surface of granular layer keratinocytes. Extracellular lipids, including ceramide, are thought to be essential for skin barrier function. ABCA12 mutations are known to underlie the three main types of autosomal recessive congenital ichthyoses: harlequin ichthyosis, lamellar ichthyosis and congenital ichthyosiform erythroderma. ABCA12 mutations lead to defective lipid transport via lamellar granules in the keratinocytes, resulting in malformation of the epidermal lipid barrier and ichthyosis phenotypes. Studies of ABCA12-deficient model mice indicate that lipid transport by ABCA12 is also indispensable for intact differentiation of keratinocytes.

Br J Dermatol. 2011 Oct; 165(4): 906-11
Rodríguez-Pazos L, Ginarte M, Fachal L, Toribio J, Carracedo A, Vega A

  Mutations in six genes have been identified in autosomal recessive congenital ichthyosis (ARCI). To date, few studies have analysed the spectrum of these mutations in specific populations.We have studied the characteristics of patients with ARCI in Galicia (NW Spain). Methods  We recruited patients by contacting all dermatology departments of Galicia and the Spanish patient organization for ichthyosis. TGM1, ALOX12B, ALOXE3, NIPAL4 and CYP4F22 were analysed in the patients and their relatives.We identified 23 patients with ARCI and estimated a prevalence of 1 : 122 000. Twenty of the patients were studied. Seventeen of them were clinically categorized as having lamellar ichthyosis (LI) and three as having congenital ichthyosiform erythroderma (CIE). TGM1 and ALOXE3 mutations were identified in 12/16 (75%) probands whereas no ALOX12B, NIPAL4 and CYP4F22 mutations were found. TGM1 mutations were found in 11/13 (85%) of LI probands. ALOXE3 mutations were identified in a single patient with CIE. Remarkably, mutations p.Arg760X, p.Asp408ValfsX21 and c.984+1G>A of TGM1 were present in six, four and two families, accounting for 41%, 23% and 14% of all TGM1 mutant alleles, respectively.The high percentage of patients with the same TGM1 mutations, together with the high number of homozygous probands (64%), indicates the existence of a strong founder effect in our population.