Isotretinoin treatment of Darier's disease

Darier disease: Current insights and challenges in pathogenesis and management

Darier disease is a rare autosomal dominant genodermatosis caused by mutations in the ATP2A2 gene encoding for sarcoendoplasmic reticulum Ca2+ ATPase isoform 2. The skin disease is characterized by a chronic relapsing course with recurrent reddish-brown keratotic papules and plaques located mainly in seborrhoeic areas. Due to chronic inflammation and epidermal barrier defects of the skin, patients often develop severe bacterial and viral superinfections. Therapeutic options are limited, mainly symptomatic and in most cases unsatisfactory in the long term. Patients are advised to avoid aggravating factors such as high temperature, high humidity, UV radiation and mechanical irritation. To prevent superinfection, antiseptics and periodic use of topical corticosteroids are fundamental in treatment. In case of bacterial and viral superinfection, systemic anti-infective therapy is often necessary. Currently, the most effective treatment option for extensive and persistent skin lesions is systemic retinoids, which are thought to mainly target the epidermal compartment (e.g. by reducing hyperkeratosis). One hallmark of Darier disease patients is chronic skin inflammation. We and others have previously reported Th17 cells in the dermal infiltrate of inflamed Darier disease skin. Counteracting inflammation by blocking the IL-23/IL-17 axis improved skin manifestations in a small cohort of previously therapy-resistant patients over 1 year. Furthermore, several other topical treatment options for mild disease as well as various ablative therapies and surgical excision have been proposed to be effective in some patients with hypertrophic skin lesions. This article aims to outline the pathogenesis, clinical features, diagnosis/differential diagnosis and available treatment modalities of Darier disease.

Th17-associated cytokines IL-17 and IL-23 in inflamed skin of Darier disease patients as potential therapeutic targets

Darier disease (DD) is a rare, inherited multi-organ disorder associated with mutations in the ATP2A2 gene. DD patients often have skin involvement characterized by malodorous, inflamed skin and recurrent, severe infections. Therapeutic options are limited and inadequate for the long-term management of this chronic disease. The aim of this study was to characterize the cutaneous immune infiltrate in DD skin lesions in detail and to identify new therapeutic targets. Using gene and protein expression profiling assays including scRNA sequencing, we demonstrate enhanced expression of Th17-related genes and cytokines and increased numbers of Th17 cells in six DD patients. We provide evidence that targeting the IL-17/IL-23 axis in a case series of three DD patients with monoclonal antibodies is efficacious with significant clinical improvement. As DD is a chronic, relapsing disease, our findings might pave the way toward additional options for the long-term management of skin inflammation in patients with DD.

Targeting SERCA2 in organotypic epidermis reveals MEK inhibition as a therapeutic strategy for Darier disease

Mutation of the ATP2A2 gene encoding sarco-endoplasmic reticulum calcium ATPase 2 (SERCA2) was linked to Darier disease more than 2 decades ago; however, there remain no targeted therapies for this disorder causing recurrent skin blistering and infections. Since Atp2a2-knockout mice do not phenocopy its pathology, we established a human tissue model of Darier disease to elucidate its pathogenesis and identify potential therapies. Leveraging CRISPR/Cas9, we generated human keratinocytes lacking SERCA2, which replicated features of Darier disease, including weakened intercellular adhesion and defective differentiation in organotypic epidermis. To identify pathogenic drivers downstream of SERCA2 depletion, we performed RNA sequencing and proteomics analysis. SERCA2-deficient keratinocytes lacked desmosomal and cytoskeletal proteins required for epidermal integrity and exhibited excess MAPK signaling, which modulates keratinocyte adhesion and differentiation. Immunostaining patient biopsies substantiated these findings, with lesions showing keratin deficiency, cadherin mislocalization, and ERK hyperphosphorylation. Dampening ERK activity with MEK inhibitors rescued adhesive protein expression and restored keratinocyte sheet integrity despite SERCA2 depletion or chemical inhibition. In sum, coupling multiomic analysis with human organotypic epidermis as a preclinical model, we found that SERCA2 haploinsufficiency disrupts critical adhesive components in keratinocytes via ERK signaling and identified MEK inhibition as a treatment strategy for Darier disease.

Targeting SERCA2 in organotypic epidermis reveals MEK inhibition as a therapeutic strategy for Darier disease

Mutation of the ATP2A2 gene encoding sarco-endoplasmic reticulum calcium ATPase 2 (SERCA2) was linked to Darier disease more than two decades ago; however, there remain no targeted therapies for this disorder causing recurrent skin blistering and infections. Since Atp2a2 knockout mice do not phenocopy its pathology, we established a human tissue model of Darier disease to elucidate its pathogenesis and identify potential therapies. Leveraging CRISPR/Cas9, we generated human keratinocytes lacking SERCA2, which replicated features of Darier disease, including weakened intercellular adhesion and defective differentiation in organotypic epidermis. To identify pathogenic drivers downstream of SERCA2 depletion, we performed RNA sequencing and proteomic analysis. SERCA2-deficient keratinocytes lacked desmosomal and cytoskeletal proteins required for epidermal integrity and exhibited excess MAP kinase signaling, which modulates keratinocyte adhesion and differentiation. Immunostaining patient biopsies substantiated these findings with lesions showing keratin deficiency, cadherin mis-localization, and ERK hyper-phosphorylation. Dampening ERK activity with MEK inhibitors rescued adhesive protein expression and restored keratinocyte sheet integrity despite SERCA2 depletion or chemical inhibition. In sum, coupling multi-omic analysis with human organotypic epidermis as a pre-clinical model, we found that SERCA2 haploinsufficiency disrupts critical adhesive components in keratinocytes via ERK signaling and identified MEK inhibition as a treatment strategy for Darier disease.

Darier's follicular dyskeratosis

Darier's follicular dyskeratosis (synonym: Dariers disease, DarierWhites disease) is a rare genetic disease with an autosomal dominant type of inheritance, which belongs to the group of acantholytic dermatoses and is characterized by a violation of keratinization processes with lesions of the skin, nails, mucous membranes of the oral cavity and genitals. Dariers disease is caused by a mutation in the ATP2A2 gene. This disrupts the operation of the SERCA2 pump and leads to a violation of calcium homeostasis in keratinocytes and a decrease in intercellular adhesion. Dariers disease is manifested by brownish papules in seborrheic and intertriginal areas with a keratotic surface, which can merge into macerated plaques. Typical nail changes in Dariers disease include red and white longitudinal stripes ending in V-shaped notches on the free edge of the nail plates. Warty acrokeratosis, as well as bullous, hemorrhagic, comedonic and linear-segmental types are clinical variants of Dariers disease. Dariers disease is often associated with neuropsychiatric disorders. Exacerbation may be caused by superinfection with Staphylococcus aureus or by herpes simplex virus. Histology in Darieres disease is characterized by pronounced dyskeratosis. For local therapy, keratolytic agents are important, as well as antiseptic treatment to avoid superinfection. In addition, local corticosteroids are used. Among the systemic methods of treatment, the systemic retinoids are the most effective. Ablative methods of treatment (dermabrasion, CO2 laser, Er:YAG laser) are effective in limited areas.

Therapeutic Options for the Treatment of Darier's Disease: A Comprehensive Review of the Literature

Darier's disease (also known as keratosis follicularis or dyskeratosis follicularis) is an autosomal dominant inherited disorder which manifests as hyperkeratotic greasy papules in the first or second decade of life. Aside from symptom management and behavioral modifications to avoid triggers, there are currently no validated treatments for Darier's disease (DD). However, a variety of treatments have been proposed in the literature including retinoids, steroids, vitamin D analogs, photodynamic therapy, and surgical excision. The purpose of this review article is to identify therapeutic options for treating DD and to outline the evidence underlying these interventions. A search was conducted in Medline for English language articles from inception to July 4, 2020. Our search identified a total of 474 nonduplicate studies, which were screened by title and abstract. Of these, 155 full text articles were screened against inclusion/exclusion criteria, and 113 studies were included in our review. We identified Grade B evidence for the following treatments of DD: oral acitretin, oral isotretinoin, systemic Vitamin A, topical tretinoin, topical isotretinoin, topical adapalene gel, topical 5-flououracil, topical calciptriol and tacalcitol (with sunscreen), grenz ray radiation, and x-ray radiation. All other evidence for treatments of DD consisted of case reports or case series, which is considered grade C evidence. Considering the quality and quantity of evidence, clinicians may consider initiating a trial of select topical or oral retinoids first in patients with localized or generalized DD, respectively.

Darier and Hailey-Hailey disease: update 2021

The autosomal-dominant genodermatoses Darier disease and Hailey-Hailey disease present special challenges to dermatologists. Despite their similar pathogenesis featuring impaired adhesion of suprabasal keratinocytes as a result of defective ATPases in epidermal calcium channels, the two diseases differ considerably in clinical presentation and therapeutic options. Darier disease is characterized by reddish brown, keratotic papules in seborrheic and intertriginous areas, which may coalesce into extensive lesions. Individuals affected with Hailey-Hailey disease primarily develop intertriginous papulovesicles and small blisters, which often evolve into erythematous plaques with erosions and painful fissures. Quality of life is significantly reduced because of complaints (itch, burning sensation, pain), body malodor and chronicity. Therapeutic options remain limited. Antiseptics and intermittent topical corticosteroids are a cornerstone of therapy, and systemic anti-infective treatment is often required in cases of superinfection. Ablative surgical interventions such as dermabrasion and CO₂ laser surgery can lead to long-term remissions in intertriginous Hailey-Hailey disease, while temporary relief may also be achieved by intralesional injections of botulinum toxin. Of the systemic medications available for Darier disease, acitretin, which is approved for this purpose, has the best supporting evidence. The efficacy of immunosuppressants and immune modulators is inconsistent. Low-dose naltrexone produces more satisfactory results in Hailey-Hailey than Darier disease. The present CME article summarizes current knowledge of the two dermatoses, taking recent developments into account.

Preclinical assessment of dual CYP26[A1/B1] inhibitor, DX308, as an improved treatment for keratinization disorders

Background

Retinoid‐based therapies are commonly used in the treatment of disorders of keratinization and other skin disorders but can result in non‐specific effects and adverse reactions. Use of retinoic acid metabolism blocking agents (RAMBAs) such as DX308 may address these shortcomings.

Objectives

Characterize the therapeutic potential of recently discovered, CYP26‐selective RAMBA, DX308.

Materials and Methods

Preliminary in vitro assessment of potential off‐target activity, metabolic and toxicologic profiling. Studies to assess safety and efficacy of topical treatment in correcting abnormal skin morphology in rhino mice. Extensive gene expression profiling by RNA sequencing and qPCR in 3D epidermis grown with keratinocytes (KCs) from keratinization disorders and healthy controls, to investigate modulation of retinoid biopathways.

Results

In vitro, DX308 does not interact with off‐target nuclear receptors or CYP450s, is not genotoxic, and is stable in skin, despite vigorous hepatic metabolism. In vivo, topical DX308 induces comedolysis and epidermal thickening without apparent adverse effects. Gene expression profiling shows potent modulation of retinoid‐responsive genes by DX308 in both healthy and keratinization disorder KCs. Pathway analysis suggests DX308 may inhibit inflammatory and immune responses in KCs.

Conclusions

These preliminary studies suggest that DX308 is an efficacious topical therapeutic with a favourable metabolic and safety profiles. DX308 may present an improved therapeutic alternative for the treatment of keratinization disorders and other retinoid‐responsive skin ailments.

Management of Darier disease: A review of the literature and update

Darier disease (DD) is a rare type of inherited keratinizing disorder with no definitive therapeutic approach. The objective of this study is to provide a detailed literature review of all the available treatment modalities of Darier disease, including those that are both surgical and non surgical, to compare their efficacies and to propose a novel therapeutic approach. A complete search of the literature for all articles describing the different treatments of Darier disease, with no restrictions on patients' ages, gender or nationalities, was performed with the use of PubMed. A total of 68 articles were included in the study: 3 prospective studies, 44 case reports/case series and 21 letters/correspondences/clinical images. The treatments described were topical, oral or physical. Retinoids (isotretinoin, tazarotene and adapalene) and fluorouracil were the two most effective topical treatments. Oral retinoids were the most effective oral therapy and were prescribed in the cases of generalized Darier disease. For localized and resistant skin lesions, physical therapies including surgical excision, dermabrasion and CO2 laser ablation were the first line choices. Limitations of this article include the inability to verify the accuracy of the published data, the relatively small sample size, the absence of randomized controlled clinical trials and possible unidentified confounding factors in various studies. In every therapeutic approach to Darier disease, consideration of patient comorbidities, disease distribution, severity and treatment accessibility is essential. Large and randomized clinical trials are necessary for the comparison of the efficacy and the safety of all the treatments of Darier disease and settling a consensus for management.

Consensus recommendations for the use of retinoids in ichthyosis and other disorders of cornification in children and adolescents

Topical and systemic retinoids have long been used in the treatment of ichthyoses and other disorders of cornification. Due to the need for long-term use of retinoids for these disorders, often beginning in childhood, numerous clinical concerns must be considered. Systemic retinoids have known side effects involving bone and eye. Additionally, potential psychiatric and cardiovascular effects need to be considered. Contraceptive concerns, as well as the additive cardiovascular and bone effects of systemic retinoid use with hormonal contraception must also be deliberated for patients of childbearing potential. The Pediatric Dermatology Research Alliance (PeDRA) Use of Retinoids in Ichthyosis Work Group was formed to address these issues and to establish best practices regarding the use of retinoids in ichthyoses based on available evidence and expert opinion.

Oral isotretinoin for the treatment of dermatologic conditions other than acne: a systematic review and discussion of future directions

While isotretinoin has been the gold-standard of therapy for severe acne since its approval in 1982, its anti-inflammatory properties makes it a potentially applicable and versatile therapy for a wide variety of dermatologic conditions yet to be explored. This systematic review comprehensively recounts the success of oral isotretinoin in non-acne cutaneous diseases and provide insight into future directions of isotretinoin utility. A systematic literature review was performed using PubMed. Search terms included "isotretinoin" OR "accutane" AND "skin" OR "dermatology" OR "hair" OR "nails" OR "rosacea" OR "psoriasis" OR "pityriasis rubra pilaris" OR "condyloma acuminata" OR "granuloma annulare" OR "darier's disease" OR "non-melanoma skin cancer" OR "frontal fibrosing alopecia" OR "cutaneous lupus erythematosus" OR "hidradenitis suppurativa" OR "photodamaged skin" OR "skin aging" OR "wart" OR "flat warts" OR "plane warts" OR "lichen planus" OR "dissecting cellulitis" OR "folliculitis decalvans" OR "sebaceous hyperplasia" OR "cutaneous t-cell lymphoma" OR "mycosis fungoides." A total of 169 studies discuss the use of oral isotretinoin for 16 non-acne dermatologic conditions, the most common being non-melanoma skin cancers (0.2-8.2 mg/kg/day), cutaneous T-cell lymphomas (0.5-2 mg/kg/day), and rosacea (0.22-1 mg/kg/day). Inflammatory conditions such as rosacea, granuloma annulare, and hidradenitis suppurativa benefit from lower oral isotretinoin dosage of 0.3-1 mg/kg/day, whereas, hyperkeratotic diseases such as psoriasis and pityriasis rubra pilaris, consistently respond better to higher dosages of up to 2-4 mg/kg/day for lesion clearance. Recurrence of disease following discontinuation of isotretinoin have been reported for rosacea, psoriasis, granuloma annulare, Darier's disease, dissecting cellulitis, and non-melanoma skin cancers. Disease exacerbation was reported in some patients with hidradenitis suppurativa. Off-label isotretinoin is an effective treatment choice for dermatological conditions beyond acne. Further prospective, randomized human trials are needed to clarify when and how to prescribe off-label isotretinoin for maximum efficacy and safety.

Characterization of CYP26B1-Selective Inhibitor, DX314, as a Potential Therapeutic for Keratinization Disorders

Inhibition of CYP450-mediated retinoic acid (RA) metabolism by RA metabolism blocking agents increases endogenous retinoids and is an alternative to retinoid therapy. Currently available RA metabolism blocking agents (i.e., liarozole and talarozole) tend to have fewer adverse effects than traditional retinoids but lack target specificity. Substrate-based inhibitor DX314 has enhanced selectivity for RA-metabolizing enzyme CYP26B1 and may offer an improved treatment option for keratinization disorders such as congenital ichthyosis and Darier disease. In this study, we used RT-qPCR, RNA sequencing, pathway, upstream regulator, and histological analyses to demonstrate that DX314 can potentiate the effects of all-trans-RA in healthy and diseased reconstructed human epidermis. We unexpectedly discovered that DX314, but not all-trans-RA or previous RA metabolism blocking agents, appears to protect epidermal barrier integrity. In addition, DX314-induced keratinization and epidermal proliferation effects are observed in a rhino mice model. Altogether, the results indicate that DX314 inhibits all-trans-RA metabolism with minimal off-target activity and shows therapeutic similarity to topical retinoids in vitro and in vivo. Findings of a barrier-protecting effect require further mechanistic study but may lead to a unique strategy in barrier-reinforcing therapies. DX314 is a promising candidate compound for further study and development in the context of keratinization disorders.

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.

Comedolytic effect of topically applied active vitamin D3 analogue on pseudocomedones in the rhino mouse

BACKGROUND

Retinoids and active vitamin D(3) analogues regulate the proliferation and differentiation of keratinocytes and are effective in the treatment of psoriasis. Retinoids are known to be effective against acne vulgaris through comedolysis. However, the comedolytic effect of active vitamin D(3) analogues has not been reported.

OBJECTIVES

To investigate whether maxacalcitol, one of the active vitamin D(3) analogues, has a comedolytic effect by using spontaneously comedogenic rhino mice.

METHODS

Rhino mice were treated topically with tretinoin and maxacalcitol once daily for 2 and 4 weeks, respectively. The dermal side of the epidermal sheet was observed to determine the size of the utricle. Haematoxylin and eosin-stained vertical sections were used to measure utricle diameter and density and to evaluate histological changes.

RESULTS

Maxacalcitol (25 microg g(-1)) and tretinoin (0.1%) significantly decreased the size and the diameter of the utricle after 1 week of treatment. However, maxacalcitol did not affect the density while tretinoin did have an effect. Histopathologically, maxacalcitol and tretinoin markedly induced epidermal hyperplasia accompanied by a minor accumulation of inflammatory cells in the dermis, with and without hypercornification, respectively.

CONCLUSIONS

These results indicate that maxacalcitol has a prominent effect on comedolysis and that its mechanism of action may be different from that of retinoids.

Darier's disease: epidemiology, pathophysiology, and management

Darier's disease is a rare cutaneous disease with an autosomal dominant mode of inheritance. Greasy papules and plaques arise on the seborrheic areas and in the flexures and almost all patients have nail abnormalities. Acantholysis and dyskeratosis are the typical histological findings. The underlying defect is a result of mutations in the ATP2A2 gene on chromosome 12q23-24 that encodes for a sarco/endoplasmic reticulum calcium ATPase (SERCA 2). Acantholysis is thought to result from desmosome breakdown. Darier's disease is an example of a dominantly inherited disease caused by haplo-insufficiency. Oral retinoids are the most effective treatment but their adverse effects are troublesome. Topical retinoids, topical corticosteroids, surgery, and laser surgery have their advocates but evidence for efficacy is sparse.

Management of Darier's disease

Darier's disease is an uncommon inherited cutaneous disease which is difficult to manage, especially in adolescence. The warty keratotic papules irritate, smell and look unsightly. Histologically, the condition is characterized by the presence of focal acantholytic dyskeratosis. Treatment is unsatisfactory, particularly in patients with erosive flexural disease, but retinoids reduce the hyperkeratosis. Now the mutation causing Darier's disease has been identified, there is a real possibility of more effective treatment in the future.

Topical treatment of ichthyoses and Darier's disease with 13-cis-retinoic acid. A clinical and immunohistochemical study

In a bilaterally paired double-blind comparison study, a cream containing 0.1% 13-cis-retinoic acid (13-cis-RA) and cream base only were applied over 4 weeks in seven patients with non-erythrodermic lamellar ichthyosis (NELI), two patients with Darier's disease and one patient with autosomal dominant ichthyosis vulgaris (ADIV). In two patients with NELI and two patients with Darier's disease a half-side effect was observed in favour of the side treated with 13-cis-RA. In three patients an induction of cytokeratin-4, and in one of these patients expression of cytokeratin-13, were observed after therapy. Topical 13-cis-RA appears to be a promising approach in the treatment of disorders of keratinization. The selective modulation of the cytokeratin pattern may provide an immunohistochemical tool to investigate the mode of action of retinoids.

Isotretinoin differs from other synthetic retinoids in its modulation of human cellular retinoic acid binding protein (CRABP)

Isotretinoin differs from acitretin and Ro137410 by its striking sebostatic effect in acne after oral, but not topical, administration. The reason for this is not yet understood. Previous studies indicate that cellular retinoic acid binding protein (CRABP) might be implicated in the action of synthetic retinoids. We, therefore, compared the three retinoids for their ability to increase epidermal CRABP levels after systemic and topical treatment. Oral treatment with acitretin and Ro137410 led to a striking increase of epidermal CRABP (from 2.6 +/- 0.9 to 16.2 +/- 2.9, P less than 0.004 and from 2.5 +/- 1.2 to 21.5 +/- 3.4 pmol/mg protein, P less than 0.004, respectively), while isotretinoin failed to induce a comparable rise (3.2 +/- 1.6 before and 3.7 +/- 0.7 pmol/mg protein after treatment), although it displayed in all patients a striking sebostatic effect. After topical application, the increase of CRABP was comparable for all three compounds. The interaction of isotretinoin with the epidermis seems to be different from other synthetic retinoids only after systemic treatment, a finding that parallels clinical observations.

Anti-oxidant effects of retinoids on inflammatory skin diseases

It is well known that retinoids are effective in the treatment of various dermatological disorders. It has been reported that retinoids have inhibitory effects on the generation of superoxide (O2-) by stimulated polymorphonuclear leukocytes (PMNs). In the present study, we investigated the effects of retinoids on the generation of O2- and other reactive oxygen species (ROS), including OH., H2O2 and chemiluminescence, by zymosan-stimulated PMNs and in the xanthine-xanthine oxidase system, because these potent ROS may play an important role in PMN-mediated skin inflammation. It was found that some retinoids had antioxidant effects in the PMN system; however, apart from the effect of tretinoin and Ro 10-1670 on OH. generation, none of the retinoids studied inhibited ROS generation in the xanthine-xanthine oxidase system. On the basis of these results, we discuss a possible mechanism connected with the role of ROS by which retinoids have favourable effects on several inflammatory skin disorders.

The surgical treatment of hypertrophic Darier's disease

Simple surgical debridement under local anesthesia of a recalcitrant case of severe hypertrophic Darier's disease provided symptomatic and cosmetic improvement for 2 years.

Retinoids: a review

The retinoids are synthetic derivatives of vitamin A. Isotretinoin (13-cis-retinoic acid) is now being widely used in the United States for severe acne and etretinate is available in Europe and other countries for psoriasis. These drugs are also effective for a number of other skin diseases. This is an attempt to review basic knowledge of retinoids with which the practicing dermatologist should be familiar, to review the current status of studies, and to speculate on the present and future roles of these drugs in dermatology.

Topical and systemic effects of retinoids on horn-filled utriculus size in the rhino mouse. A model to quantify "antikeratinizing" effects of retinoids

A method was developed to quantify the "antikeratinizing" effects of various retinoids (all-trans-retinoic acid, 13-cis-retinoic acid, motretinide, etretinate) in rhino mouse skin, which contains many keratinized pilosebaceous structures or horn-filled utriculi. Mean utriculus diameters in whole mount epidermis were determined and dose-response relationships were constructed after topical or oral administration of test retinoids. All-trans-retinoic acid was 3.7x, 12.5x, and 50x more potent than 13-cis-retinoic acid, etretinate, and motretinide, respectively, after topical administration. Administered orally, all-trans-retinoic acid was 2.3x more potent than 13-cis-retinoic acid. At 5 mg/kg, each retinoid produced a significant reduction in utriculus size. The rhino mouse model represents a novel and useful assay to quantify antikeratinizing activity and potency differences of biologically active retinoids.

Dermatologic therapy: December, 1981, through November, 1982

In this paper I have reviewed the literature on dermatologic therapy from December, 1981, through November, 1982. This information was presented to a forum at the 41st Annual Meeting of the American Academy of Dermatology in New Orleans in December, 1982. Readers should review the original article in toto before attempting any new, experimental, or controversial therapy summarized.