Targeting epidermal lipids for treatment of Mendelian disorders of cornification

French national protocol for the management of congenital ichthyosis

Congenital ichthyoses (CI) comprise a heterogeneous group of monogenic genetic skin diseases characterized by diffuse scaling, often associated with skin inflammation. Diagnosis of the individual form of ichthyosis is complex and is guided by clinical expertise. CI usually has a major impact on quality of life (QOL) and thus requires lifelong treatment. To date, there are no curative therapies, although various symptomatic treatment options exist. The present protocol for the management of CI has been drawn up in accordance with the recommendations published in 2012 by the French National Authority for Health, based on a literature review, with the help and validation of members of the French network for rare skin diseases (FIMARAD). It provides a summary of evidence and expert-based recommendations and is intended to help clinicians with the management of these rare and often complex diseases.

Crosstalk between cholesterol metabolism and psoriatic inflammation

Psoriasis is a chronic autoinflammatory skin disease associated with multiple comorbidities, with a prevalence ranging from 2 to 3% in the general population. Decades of preclinical and clinical studies have revealed that alterations in cholesterol and lipid metabolism are strongly associated with psoriasis. Cytokines (tumor necrosis factor-α (TNF-α), interleukin (IL)-17), which are important in the pathogenesis of psoriasis, have been shown to affect cholesterol and lipid metabolism. Cholesterol metabolites and metabolic enzymes, on the other hand, influence not only the biofunction of keratinocytes (a primary type of cell in the epidermis) in psoriasis, but also the immune response and inflammation. However, the relationship between cholesterol metabolism and psoriasis has not been thoroughly reviewed. This review mainly focuses on cholesterol metabolism disturbances in psoriasis and their crosstalk with psoriatic inflammation.

Use of Topical Glycolic Acid Plus a Lovastatin-Cholesterol Combination Cream for the Treatment of Autosomal Recessive Congenital Ichthyoses

Importance

Autosomal recessive congenital ichthyosis (ARCI) is a heterogeneous group of disorders caused by defects in signaling pathways involved in epidermal proliferation and differentiation, leading to a wide range of skin manifestations. Therapeutic options are limited and often unsatisfactory. Topical cholesterol and statin as a combined formulation has proven successful in the treatment of patients with CHILD syndrome (congenital hemidysplasia ichthyosis and limb defects).

Objective

To assess change in disease severity score after a 3-month therapeutic regimen consisting of a glycolic acid, 10% to 20%, cream and a combination cream of lovastatin, 2%, with cholesterol, 2%, in the treatment of ARCI.

Design, Setting, and Participants

This case series of 15 patients with ARCI was conducted at the American University of Beirut, a referral center in the Middle East region for genodermatoses, between May 2017 and January 2018. No age groups were excluded; all patients were from the Middle East area; and all were initially not responsive to treatment with hydrating creams in combination with urea creams, 30% to 40%, or glycolic acid, 10% to 20%. Excluded were patients who had been taking systemic retinoids within 3 months before the start of the study.

Interventions

A 3-month therapeutic regimen of glycolic acid, 10% to 20%, cream and a combination of lovastatin, 2%, with cholesterol, 2%, cream.

Main Outcomes and Measures

Percentage change in disease severity scores following 2 and 3 months of study treatment.

Results

Of the 15 patients included in the study, 10 were male (mean age, 11.2 years; age range, 2-38 years). The average percentage reduction in the disease severity score was 33.7% at 2 months (from 60.8 to 40.2) and 57.5% at 3 months (from 60.8 to 21.9). Adverse effects were mild and consisted mainly of irritation and burning.

Conclusions and Relevance

These findings suggest a benefit from a treatment regimen consisting of glycolic acid, 10% to 20%, and a combination of lovastatin, 2%, with cholesterol, 2%, in the treatment of ARCI. This combination of creams might also prove to be beneficial in other types of ichthyoses and other dermatological diseases with a defective skin barrier.

Management of congenital ichthyoses: European guidelines of care, part one

These guidelines for the management of congenital ichthyoses have been developed by a multidisciplinary group of European experts following a systematic review of the current literature, an expert conference held in Toulouse in 2016 and a consensus on the discussions. They summarize evidence and expert-based recommendations and are intended to help clinicians with the management of these rare and often complex diseases. These guidelines comprise two sections. This is part one, covering topical therapies, systemic therapies, psychosocial management, communicating the diagnosis and genetic counselling.

CHILD syndrome: A modified pathogenesis-targeted therapeutic approach

Congenital Hemidysplasia with Ichthyosiform nevus and Limb Defects (CHILD syndrome) is a rare X-linked dominant genodermatosis caused by mutations in the NAD(P) dependent steroid dehydrogenase-like protein gene. Its defect leads to accumulation of toxic metabolic intermediates upstream from the pathway block and to the deficiency of bulk cholesterol, probably leading to altered keratinocyte membrane function, resulting in the phenotype seen in CHILD syndrome. Symptomatic treatment using emollients and retinoids to reduce scaling has long been used until recently, whereby new therapeutic means based on the pathogenesis-targeted therapy have been developed. We subsequently chose to use the same pathogenesis-based therapy using a 2% cholesterol and 2% lovastatin cream with or without glycolic acid in two of our patients. Improvement in CHILD skin lesions was seen as early as 4 weeks after initiation. The addition of glycolic acid helped improve the penetrance of the cholesterol and lovastatin cream into the thick waxy scales. Our study confirms the efficacy of the pathogenesis-targeted therapy and introduces the possibility of modifying its formula by adding glycolic acid in order to improve the treatment.

Update on Genetic Conditions Affecting the Skin and the Kidneys

Genetic conditions affecting the skin and kidney are clinically and genetically heterogeneous, and target molecular components present in both organs. The molecular pathology involves defects of cell-matrix adhesion, metabolic or signaling pathways, as well as tumor suppressor genes. This article gives a clinically oriented overview of this group of disorders, highlighting entities which have been recently described, as well as the progress made in understanding well-known entities. The genetic bases as well as molecular cell biological mechanisms are described, with therapeutic applications.

Mutations in SULT2B1 Cause Autosomal-Recessive Congenital Ichthyosis in Humans

Ichthyoses are a clinically and genetically heterogeneous group of genodermatoses associated with abnormal scaling of the skin over the whole body. Mutations in nine genes are known to cause non-syndromic forms of autosomal-recessive congenital ichthyosis (ARCI). However, not all genetic causes for ARCI have been discovered to date. Using whole-exome sequencing (WES) and multigene panel screening, we identified 6 ARCI-affected individuals from three unrelated families with mutations in Sulfotransferase family 2B member 1 (SULT2B1), showing their causative association with ARCI. Cytosolic sulfotransferases form a large family of enzymes that are involved in the synthesis and metabolism of several steroids in humans. We identified four distinct mutations including missense, nonsense, and splice site mutations. We demonstrated the loss of SULT2B1 expression at RNA and protein levels in keratinocytes from individuals with ARCI by functional analyses. Furthermore, we succeeded in reconstructing the morphologic skin alterations in a 3D organotypic tissue culture model with SULT2B1-deficient keratinocytes and fibroblasts. By thin layer chromatography (TLC) of extracts from these organotypic cultures, we could show the absence of cholesterol sulfate, the metabolite of SULT2B1, and an increased level of cholesterol, indicating a disturbed cholesterol metabolism of the skin upon loss-of-function mutation in SULT2B1. In conclusion, our study reveals an essential role for SULT2B1 in the proper development of healthy human skin. Mutation in SULT2B1 leads to an ARCI phenotype via increased proliferation of human keratinocytes, thickening of epithelial layers, and altered epidermal cholesterol metabolism.

PNPLA1 Deficiency in Mice and Humans Leads to a Defect in the Synthesis of Omega-O-Acylceramides

Mutations in PNPLA1 have been identified as causative for autosomal recessive congenital ichthyosis in humans and dogs. So far, the underlying molecular mechanisms are unknown. In this study, we generated and characterized PNPLA1-deficient mice and found that PNPLA1 is crucial for epidermal sphingolipid synthesis. The absence of functional PNPLA1 in mice impaired the formation of omega-O-acylceramides and led to an accumulation of nonesterified omega-hydroxy-ceramides. As a consequence, PNPLA1-deficient mice lacked a functional corneocyte-bound lipid envelope leading to a severe skin barrier defect and premature death of newborn animals. Functional analyses of differentiated keratinocytes from a patient with mutated PNPLA1 demonstrated an identical defect in omega-O-acylceramide synthesis in human cells, indicating that PNPLA1 function is conserved among mammals and indispensable for normal skin physiology. Notably, topical application of epidermal lipids from wild-type onto Pnpla1-mutant mice promoted rebuilding of the corneocyte-bound lipid envelope, indicating that supplementation of ichthyotic skin with omega-O-acylceramides might be a therapeutic approach for the treatment of skin symptoms in individuals affected by omega-O-acylceramide deficiency.

CHILD syndrome with mild skin lesions: histopathologic clues for the diagnosis

CHILD syndrome is an acronym signifying congenital hemidysplasia with ichthyosiform nevus and limb defects. A 27-year-old woman presented with chronic verrucous and hyperkeratotic skin lesions involving the left genital area, left hand and left foot since childhood. The histopathologic findings were consistent with verruciform xanthoma. In correlation with the clinical picture of a linear lesion, the diagnosis of CHILD nevus was made. Subsequent genetic analysis identified a germline c.324C>T (p.A105V) NSDHL mutation and confirmed a diagnosis of CHILD syndrome. This syndrome can be associated with only minimal clinical symptoms. The anatomical distribution of the lesions, a static clinical course and the typical histopathologic features of a CHILD nevus can serve as the clue to a diagnosis of CHILD syndrome in such cases.