A longitudinal study of a harlequin infant presenting clinicallyas non-bullous congenital ichthyosiform erythroderma

Management of ocular manifestations of autosomal recessive congenital ichthyosis 4B, harlequin type, in the perinatal period

Autosomal recessive congenital ichthyosis (ARCI4B [OMIM #242500]), also known as harlequin ichthyosis, presents at birth with extreme hyperkeratosis and thick-fissured plaques, leading to tightness of the skin around the eyes, mouth, ears, chest, abdomen, and extremities. Ocular manifestations include cicatricial ectropion and exposure keratitis. We present 2 infants with ARCI4B and cicatricial ectropion who were managed with aggressive nonsurgical therapy. Both infants avoided severe ocular sequelae and maintained corneal clarity, highlighting that management of exposure keratopathy with frequent ophthalmic ointment application can prevent severe ocular surface pathology in ARCI4B.

Peptidylarginine Deiminase Inhibitor Cl-Amidine Attenuates Cornification and Interferes with the Regulation of Autophagy in Reconstructed Human Epidermis

Deimination, a post-translational modification catalyzed by a family of enzymes called peptidylarginine deiminases (PADs), is the conversion of arginine into citrulline residues in a protein. Deimination has been associated with numerous physiological and pathological processes. Our aim was to study its implication in the homeostasis of human epidermis, where three PADs are expressed, namely PAD1, 2, and 3. Three-dimensional reconstructed human epidermis (RHEs) were treated for 2 days with increased concentrations (0-800 μM) of Cl-amidine, a specific PAD inhibitor. Cl-amidine treatments inhibited deimination in a dose-dependent manner and were not cytotoxic for keratinocytes. At 800 μM , Cl-amidine was shown to reduce deimination by half, alter keratinocyte differentiation, decrease the number of corneocyte layers, significantly increase the number of transitional cells, induce clustering of mitochondria and of heterogeneous vesicles in the cytoplasm of granular keratinocytes, and upregulate the expression of autophagy proteins, including LC3-II, sestrin-2, and p62/SQSTM1. LC3 and PADs were further shown to partially co-localize in the upper epidermis. These results demonstrated that Cl-amidine treatments slow down cornification and alter autophagy in the granular layer. They suggest that PAD1 and/or PAD3 play a role in the constitutive epidermal autophagy process that appears as an important step in cornification.

Recent advances in the genetics and management of harlequin ichthyosis

Harlequin ichthyosis (HI) is the most severe and devastating form of the autosomal recessive congenital ichthyoses (ARCIs). Mutations in the ABCA12 gene result in disruption of intercellular lipid deposition in the stratum corneum and a major skin barrier defect. Patients present at birth, often premature, with cutaneous thick, yellow, hyperkeratotic plates with deep erythematous fissures, causing a typical facial appearance. Harlequin ichthyosis has often been considered to be fatal, and management tends to be palliative, but follow-up of 45 affected infants has shown that with good neonatal care and early introduction of oral retinoids, survival rates are improving. Because ABCA12 mutations have been identified, known carriers are able to undergo preventative preimplantation and prenatal genetic testing. Experimental studies have shown recovery of lipid secretion in lamellar granules using corrective gene therapy. Further research is needed to develop alternative therapies to retinoids in HI.

Techniques for toddlers: linear band incision for harlequin ichthyosis with associated compartment syndrome

Harlequin ichthyosis (HI) is a rare autosomal recessive disorder of cornification in which children are born with an extremely thick stratum corneum that becomes a restrictive circumferential encasement around the orifices, limbs, chest, and abdomen, resulting in limb contractures. We present a neonate diagnosed in utero with HI. The infant was born with encasing bands of thickened skin creating strictures that were causing digital and limb cyanosis (compartment syndrome). We treated the child using a new technique of lysis of the encasing bands that we call linear band incision, using a new escharotomy-like procedure while the infant was undergoing a 3-week course oral acitretin therapy. The technique involved linear incision and lysis of encasements that resulted in reperfusion of the injured limbs and prevention of further digital necrosis. The child is currently a healthy 8-year-old boy with skin manifestations resembling congenital ichthyosiform erythroderma. He has use of all of the limbs that were released in the procedures and is maintained on frequent application of bland emollients. Linear band incision is a potentially life- and limb-saving technique in children with HI.

Systemic retinoids in the management of ichthyoses and related skin types

The term retinoid includes both natural and synthetic derivatives of vitamin A. Retinoid-containing treatments have been used since ~1550BC by the early Egyptians. Treatment of ichthyosiform disorders with retinoids dates back at least to the 1930s. Early use of high-dose vitamin A demonstrated efficacy, but because vitamin A is stored in the liver, toxicity limited usefulness. Interest turned to synthetic retinoids in an effort to enhance efficacy and limit toxicity. Acetretin, isotretinoin and, in the past etretinate, have provided the most effective therapy for ichthyosiform conditions. They have been used for a variety of ages, including in newborns with severe ichthyosis and for decades in some patients. Careful surveillance and management of mucous membrane, laboratory, skeletal, and teratogenic side effects has made systemic retinoids the mainstay of therapy for ichthyosis and related skin types.

Autosomal recessive congenital ichthyosis

The term autosomal recessive congenital ichthyosis (ARCI) refers to a group of rare disorders of keratinization classified as nonsyndromic forms of ichthyosis. This group was traditionally divided into lamellar ichthyosis (LI) and congenital ichthyosiform erythroderma (CIE) but today it also includes harlequin ichthyosis, self-healing collodion baby, acral self-healing collodion baby, and bathing suit ichthyosis. The combined prevalence of LI and CIE has been estimated at 1 case per 138 000 to 300 000 population. In some countries or regions, such as Norway and the coast of Galicia, the prevalence may be higher due to founder effects. ARCI is genetically highly heterogeneous and has been associated with 6 genes to date: TGM1, ALOXE3, ALOX12B, NIPAL4, CYP4F22, and ABCA12. In this article, we review the current knowledge on ARCI, with a focus on clinical, histological, ultrastructural, genetic, molecular, and treatment-related aspects.

Harlequin ichthyosis: ABCA12 mutations underlie defective lipid transport, reduced protease regulation and skin-barrier dysfunction

Harlequin ichthyosis (HI) is a devastating autosomal recessive congenital skin disease. It has been vital to elucidate the biological importance of the protein ABCA12 in skin-barrier permeability, following the discovery that ABCA12 gene mutations can result in this rare disease. ATP-binding cassette transporter A12 (ABCA12) is a member of the subfamily of ATP-binding cassette transporters and functions to transport lipid glucosylceramides (GlcCer) to the extracellular space through lamellar granules (LGs). GlcCer are hydrolysed into hydroxyceramides extracellularly and constitute a portion of the extracellular lamellar membrane, lipid envelope and lamellar granules. In HI skin, loss of function of ABCA12 due to null mutations results in impaired lipid lamellar membrane formation in the cornified layer, leading to defective permeability of the skin barrier. In addition, abnormal lamellar granule formation (distorted shape, reduced in number or absent) could further cause aberrant production of LG-associated desquamation enzymes, which are likely to contribute to the impaired skin barrier in HI. This article reviews current opinions on the patho-mechanisms of ABCA12 action in HI and potential therapeutic interventions based on targeted molecular therapy and gene therapy strategies.

Perinatal management of harlequin ichthyosis: a case report and literature review

Harlequin ichthyosis (HI) is a rare and severe form of congenital ichthyosis. Linked to deletion and truncation mutations of a keratinocyte lipid transporter, HI is characterized by diffuse epidermal hyperkeratinization and defective desquamation. At birth, the HI phenotype is striking with thick hyperkeratotic plate-like scales with deep dermal fissures, severe ectropion and eclabium, among other findings. Over the first months of life, the hyperkeratotic covering is shed, revealing a diffusely erythematous, scaly epidermis, which persists for the remainder of the patient's life. Although HI infants have historically succumbed in the perinatal period related to their profound epidermal compromise, the prognosis of HI infants has vastly improved over the past 20 years. Here, we report a case of HI treated with acitretin, focusing on the multi-faceted management of the disease in the inpatient setting. A review of the literature of the management of HI during the perinatal period is also presented.

Repair of cicatricial ectropion in a harlequin baby

The ichthyoses are a collection of scaling skin diseases or keratinizing skin disorders giving the appearance of "fish skin," of which harlequin ichthyosis is the most severe form. It is characterized by profound thickening of the keratin skin layer, armorlike scales that cover the body, and contraction abnormalities of the eyes, ears, and mouth. We report a case of a 6-week-old boy with harlequin ichthyosis and severe bilateral upper and lower eyelid cicatricial ectropion who underwent surgical repair with full-thickness postauricular skin autografts. To our knowledge, this is the youngest reported case and the only case of harlequin ichthyosis in which postauricular skin grafts were used.

Premature terminal differentiation and a reduction in specific proteases associated with loss of ABCA12 in Harlequin ichthyosis

One of the primary functions of skin is to form a defensive barrier against external infections and water loss. Disrupted barrier function underlies the most severe and often lethal form of recessive congenital ichthyosis, harlequin ichthyosis (HI). HI is associated with mutations in the gene that encodes the ABC transporter protein, ABCA12. We have investigated the morphological and biochemical alterations associated with abnormal epidermal differentiation and barrier formation in HI epidermis. An in vitro model of HI skin using human keratinocytes retrovirally transduced with shRNA targeting ABCA12 in a three-dimensional, organotypic co-culture (OTCC) system has also been developed. A robust reduction in ABCA12 expression had a dramatic effect on keratinocyte differentiation and morphology comparable with that observed in HI skin, including a thicker epidermis and abnormal lipid content with a reduction in nonpolar lipids. As seen in HI epidermis, proteins that are normally expressed in late differentiation were highly dysregulated in the ABCA12-ablated OTCC system. These proteins were expressed in the stratum basale and also in the stratum spinosum, indicative of a premature terminal differentiation phenotype. Expression of the proteases kallikrein 5 and cathepsin D was dramatically reduced in both HI epidermis and the OTCC model. These data suggest that ABCA12 is a key molecule in regulating keratinocyte differentiation and transporting specific proteases associated with desquamation.

Compound Heterozygous ABCA12 Mutations Including a Novel Nonsense Mutation Underlie Harlequin Ichthyosis

Recently, it has been reported that several harlequin ichthyosis (HI) patients survive the neonatal period and their condition subsequently improves. Here we describe a 2-year-old Japanese boy who exhibited typical clinical features of HI at birth. He survived beyond the neonatal period after oral retinoid treatment and, at the age of 2 years, showed moderately thick, lamellar scales and erythroderma over his whole body. The patient is a compound heterozygote for 2 ABCA12 mutations, a paternal deletion mutation c.2021_2022del (p.Lys674ArgfsX63) and a novel maternal nonsense mutation c.7444C --> T (p.Arg2482X). Electron microscopic observation of a skin biopsy specimen from the perinatal period revealed epidermal ultrastructural features consistent with HI. Immunofluorescence labeling using antiserum against a C-terminal ABCA12 epitope showed loss of expression in the patient's epidermis. The present patient demonstrates that rapid diagnosis of HI by ABCA12 expression analysis and mutation detection, and early commencement of systemic retinoid therapy are crucial to significantly improving an HI patient's prognosis.

Stratum corneum defensive functions: an integrated view

Most epidermal functions can be considered as protective, or more specifically, as defensive in nature. Yet, the term "barrier function" is often used synonymously with only one such defensive function, though arguably its most important, i.e., permeability barrier homeostasis. Regardless of their relative importance, these protective cutaneous functions largely reside in the stratum corneum (SC). In this review, I first explore the ways in which the multiple defensive functions of the SC are linked and interrelated, either by their shared localization or by common biochemical processes; how they are co-regulated in response to specific stressors; and how alterations in one defensive function impact other protective functions. Then, the structural and biochemical basis for these defensive functions is reviewed, including metabolic responses and signaling mechanisms of barrier homeostasis. Finally, the clinical consequences and therapeutic implications of this integrated perspective are provided.

Mutations in ABCA12 underlie the severe congenital skin disease harlequin ichthyosis

Harlequin ichthyosis (HI) is the most severe and frequently lethal form of recessive congenital ichthyosis. Although defects in lipid transport, protein phosphatase activity, and differentiation have been described, the genetic basis underlying the clinical and cellular phenotypes of HI has yet to be determined. By use of single-nucleotide-polymorphism chip technology and homozygosity mapping, a common region of homozygosity was observed in five patients with HI in the chromosomal region 2q35. Sequencing of the ABCA12 gene, which maps within the minimal region defined by homozygosity mapping, revealed disease-associated mutations, including large intragenic deletions and frameshift deletions in 11 of the 12 screened individuals with HI. Since HI epidermis displays abnormal lamellar granule formation, ABCA12 may play a critical role in the formation of lamellar granules and the discharge of lipids into the intercellular spaces, which would explain the epidermal barrier defect seen in this disorder. This finding paves the way for early prenatal diagnosis. In addition, functional studies of ABCA12 will lead to a better understanding of epidermal differentiation and barrier formation.

Harlequin ichthyosis: a case study

The most severe manifestation of congenital ichthyosis presents itself in the form known as harlequin ichthyosis. Harlequin ichthyosis is characterized by a profound thickening of the fetal skin. Affected infants are born with a thick "horny shell" of dense, waxy, platelike scales with deep, irregular fissures covering the body. Contraction of the extremities is seen, along with deformities of the ears, eyes, mouth, and digits. This "armor" limits movement and compromises the skin's barrier defense, leaving the newborn at risk for metabolic abnormalities and infection. A case study of our unit's experience is provided.

De novo deletion of chromosome 18q in a baby with harlequin ichthyosis

Harlequin ichthyosis, (MIM 242500), is a rare, autosomal recessive skin disorder due to an inborn error of epidermal keratinization. The gene for this condition has not been localized. We present a case of HI in which there was a de novo deletion of chromosome 18q: the karyotype was 46, XY, del(18)(q21.3). We postulate that the gene for HI may lie at, or distal to 18q21.3 and that the deletion observed in this case may have unmasked this autosomal recessive disorder.

Harlequin fetus: a case report

We report a case of harlequin fetus. This very rare cutaneous malformation is a severe form of congenital ichthyosis. This disorder is due to an inborn error of epidermal keratinization. Malformations of ears, nose, and hypoplasia of fingers or nails are seen. This affection is most often lethal.

The major inherited disorders of cornification. New advances in pathogenesis

This article provides a synopsis of the major (most common) inherited disorders of cornification. It also reviews the recent advances that have been made for each disorder and their practical applications.