Peter R. Hull

Comprehensive analysis of the gene encoding filaggrin uncovers prevalent and rare mutations in ichthyosis vulgaris and atopic eczema

We recently reported two common filaggrin (FLG) null mutations that cause ichthyosis vulgaris and predispose to eczema and secondary allergic diseases. We show here that these common European mutations are ancestral variants carried on conserved haplotypes. To facilitate comprehensive analysis of other populations, we report a strategy for full sequencing of this large, highly repetitive gene, and we describe 15 variants, including seven that are prevalent. All the variants are either nonsense or frameshift mutations that, in representative cases, resulted in loss of filaggrin production in the epidermis. In an Irish case-control study, the five most common European mutations showed a strong association with moderate-to-severe childhood eczema (χ2 test: P = 2.12 × 10−51; Fishers exact test: heterozygote odds ratio (OR) = 7.44 (95% confidence interval (c.i.) = 4.9–11.3), and homozygote OR = 151 (95% c.i. = 20–1,136)). We found three additional rare null mutations in this case series, suggesting that the genetic architecture of filaggrin-related atopic dermatitis consists of both prevalent and rare risk alleles.

Loss-of-function variants in the filaggrin gene are a significant risk factor for peanut allergy

Background IgE-mediated peanut allergy is a complex trait with strong heritability, but its genetic basis is currently unknown. Loss-of-function mutations within the filaggrin gene are associated with atopic dermatitis and other atopic diseases; therefore, filaggrin is a candidate gene in the etiology of peanut allergy. Objective To investigate the association between filaggrin loss-of-function mutations and peanut allergy. Methods Case-control study of 71 English, Dutch, and Irish oral food challenge–positive patients with peanut allergy and 1000 non peanut-sensitized English population controls. Replication was tested in 390 white Canadian patients with peanut allergy (defined by food challenge, or clinical history and skin prick test wheal to peanut ≥8 mm and/or peanut-specific IgE ≥15 kUL−1) and 891 white Canadian population controls. The most prevalent filaggrin loss-of-function mutations were assayed in each population: R501X and 2282del4 in the Europeans, and R501X, 2282del4, R2447X, and S3247X in the Canadians. The Fisher exact test and logistic regression were used to test for association; covariate analysis controlled for coexistent atopic dermatitis. Results Filaggrin loss-of-function mutations showed a strong and significant association with peanut allergy in the food challenge–positive patients (P = 3.0 × 10−6; odds ratio, 5.3; 95% CI, 2.8-10.2), and this association was replicated in the Canadian study (P = 5.4 × 10−5; odds ratio, 1.9; 95% CI, 1.4-2.6). The association of filaggrin mutations with peanut allergy remains significant (P = .0008) after controlling for coexistent atopic dermatitis. Conclusion Filaggrin mutations represent a significant risk factor for IgE-mediated peanut allergy, indicating a role for epithelial barrier dysfunction in the pathogenesis of this disease.

Isotretinoin Use and Subsequent Depression and Suicide Presenting the Evidence

AbstractThe growing number of reported cases of depression and suicide associated with isotretinoin (a retinoid receptor agonist) use in patients with acne has prompted concern among dermatologists, patients, and their relatives and has triggered new warnings from regulators including depression-related, patient-informed consent forms. In establishing a cause-effect relationship, it is useful to judiciously consider whether there is an association, what is the nature of that association, if there is a plausible biological mechanism of action, the validity and reliability of measures used and the strength of study designs. Hoffmann-La Roche estimates that by April 2001 approximately 12 million patients worldwide have used isotretinoin, with 5 million patients in the US.A MEDLINE search between January 1966 and May 14 2003 of the published medical literature found 24 documented cases of isotretinoin-associated depression, with 3 suicides. One additional patient committed suicide during the fourth month of isotretinoin treatment and 3 further patients attempted suicide by taking an overdose of isotretinoin. The US FDA’s Adverse Event Reporting System (AERS) contains almost 23 000 reports for isotretinoin from its approval in 1982 to December 2002. As of November 30, 2002, AERS contained 3104 reports (US and foreign) with at least one reported psychiatric event. The FDA is aware of 173 reports of suicide (both US and foreign) in association with isotretinoin. Reports of positive dechallenge and rechallenge present a strong signal pointing to an association between isotretinoin and depression. A Hoffmann-La Roche sponsored epidemiological study failed to find any evidence of an association between isotretinoin and depression or suicide. However, the design of the study was flawed and the evidence was deemed inconclusive. Further studies using strong study designs, reliable and valid measures, and adequate sample sizes may bring us closer to the answer.The evidence suggesting a relationship between isotretinoin and depression needs to be weighed against the increasing prevalence of depression among adolescents and young adults and the psychological impact of acne. The literature contains credible evidence that isotretinoin treatment may reduce the psychosocial impact of acne in some patients. At the present time, there is no known pharmacological mechanism that would account for psychiatric symptomatology as a result of isotretinoin treatment; however, retinoid receptors are widely distributed in the brain and more research is needed to ascertain whether they have a role in depression.In the meantime, for the practitioner, the obvious benefit of isotretinoin in treating acne should encourage continued use. However, patients and their relatives must be informed and depressive symptoms should be actively assessed at each visit and, if necessary, referral to a psychiatrist, antidepressant therapy or discontinuation of isotretinoin should be considered.

Heterozygous Null Alleles in Filaggrin Contribute to Clinical Dry Skin in Young Adults and the Elderly

TO THE EDITOR Null mutations in the epidermal barrier protein filaggrin (FLG) cause ichthyosis vulgaris (IV, Smith et al., 2006) and are a major risk factor for eczema and other atopic diseases (Palmer et al., 2006; Baurecht et al., 2007; Brown et al., 2008a; Henderson et al., 2008). About 10% of European patients are heterozygous for such null mutations (Sandilands et al., 2006), but clinical details of their skin phenotype are sparse. A recent study of 811 English children reported that mild ichthyosis, palmar hyperlinearity, and keratosis pilaris were commoner in carriers of null mutations (Brown et al., 2008a). We report the effect of heterozygosity for FLG null alleles, and age, on the prevalence of simple subjective or objective clinical features of ‘‘dry skin’’ in adults and elderly patients not selected for inflammatory skin disease. Patients referred for diagnosis of a discrete skin lesion to dermatology clinics in Glasgow were recruited in two age cohorts: young adults 18–40 years (192 patients; 82 men, 110 women), and the elderly 60–75 years (99 patients; 55 men, 44 women). Patients were asked not to apply body moisturizers for 48 hours before their appointment; sunbed users or those who had been on a sunny holiday within 6 weeks were excluded. The protocol was approved by the South Glasgow Research Ethics Committee, conformed to the Declaration of Helsinki Principles, and written informed consent was obtained. The study took place in all months of the year, in a climate without extreme variation in humidity, and all assessments took place before genotyping. A questionnaire asked patients whether they considered they had dry skin (possible responses, coded 0–3, were not at all, a little, moderately, or a lot), sensitive skin (same responses) and how often they used a moisturizer for the body (never, now and again, more than once a week, or daily), and sought a history of childhood eczema or other diseases. Trained observers made objective assessments of visible fine scale and of roughness in each of three body sites (volar forearms, lower legs, and lower back), of keratosis pilaris (upper arms only), and of increased palmar markings and texture. A simple scoring scale for each parameter was used: absent (0), just perceptible (1), obvious (2), and marked (3). The total score of these parameters (maximum 27) was used as a summary measure of ‘‘dry skin’’. DNA, extracted from whole blood using standard procedures, was genotyped for four FLG null mutations common in the UK (R501X, 2282del4, R2447X, and S3247X) as described (Palmer et al., 2006; Sandilands et al., 2007) with minor refinements (Table S1). Statistical comparisons were made in 284 patients in whom all four mutations were successfully typed, between those wild-type sequence at all loci (wt) and patients heterozygous for only one of the mutations (null). Of 284, 252 (89%) patients were wild type for all four mutations; 29 (10.2%) were heterozygous for one null mutation, and 3 (1%) were compound heterozygotes, R501X/R2447X, 2282del4/ S3247X, and R2447X/S3247X. The frequency of these alleles was consistent with the previous UK data (Table S2; Sandilands et al., 2007; Brown et al., 2008b). Four patients in whom the assessors commented on marked scaling consistent with IV included all three compound heterozygotes; the fourth was heterozygous only for R501X but on biopsy showed a reduced granular layer, consistent with previous immunohistochemical analysis indicative of an undetected second null mutation (Sandilands et al., 2007); for financial reasons, this patient was not subjected to full sequencing. Questionnaire results are shown in Figure 1a and Table S3. Women were highly significantly more likely than men to consider they had dry skin (39 vs 11%) or use body moisturizers regularly (43 vs 7%). Heterozygous carriers of null mutations were more likely to think they had dry skin Abbreviation: FLG, filaggrin; IV, ichthyosis vulgaris

Isotretinoin use in acne: prospective evaluation of adverse events.

Background: Isotretinoin is an effective treatment for severe acne. Although the spectrum of side effects has been well documented, the changing incidence of such side effects over the course of treatment has not been studied in detail. Objectives: The purpose of our study was to examine a group of patients monthly over their course of treatment and prospectively document the side effects experienced. Methods: Over the period between January 1991 and July 1996, 124 courses of treatment with isotretinoin for severe acne were followed. The patients were treated for 4 months at a dose of 1 mg per kg body weight. A questionnaire was administered monthly, inquiring specifically about side effects known to be associated with isotretinoin. Any additional side effects were also noted. Results: The majority of patients experienced persistent dryness of lips. Dry eyes affected 40% of patients; this continued throughout treatment in 25%. Contact lens wearers were more likely to develop conjunctivitis. Lower back pain was reported early in about 30% of patients and fewer than 10% of patients would develop it later in the course of treatment. Arthralgia was noted in 16.5% of patients at the first visit and there was little change with ongoing treatment. Hair loss was experienced in a small percentage but was rarely noted on more than one occasion. Headaches occurred in less than 10% and were occasionally severe, but most often intermittent and recorded at a single visit. Depression occurred in 4% of patients and tended to persist throughout the treatment. All these patients completed the full course of treatment. Conclusion: This prospective analysis has shown that patients treated with isotretinoin experienced a predictable series of side effects. Some occurred fleetingly, but several persisted for the duration of treatment.

A Large Mutational Study in Pachyonychia Congenita

Pachyonychia congenita (PC) is a rare autosomal dominant skin disorder characterized predominantly by nail dystrophy and painful palmoplantar keratoderma. Additional clinical features include oral leukokeratosis, follicular keratosis, and cysts (steatocysts and pilosebaceous cysts). PC is due to heterozygous mutations in one of four keratin genes, namely, KRT6A, KRT6B, KRT16, or KRT17. Here, we report genetic analysis of 90 new families with PC in which we identified mutations in KRT6A, KRT6B, KRT16, or KRT17, thereby confirming their clinical diagnosis. A total of 21 previously unreported and 22 known mutations were found. Approximately half of the kindreds had mutations in KRT6A (52%), 28% had mutations in KRT16, 17% in KRT17, and 3% of families had mutations in KRT6B. Most of the mutations were heterozygous missense or small in-frame insertion/deletion mutations occurring within one of the helix boundary motif regions of the keratin polypeptide. More unusual mutations included heterozygous splice site mutations, nonsense mutations, and a 1-bp insertion mutation, leading to a frameshift and premature termination codon. This study, together with previously reported mutations, identifies mutation hotspot codons that may be useful in the development of personalized medicine for PC.

HLA-DQB1*02 and DQB1*06:03P are associated with peanut allergy

Peanut allergy (PA) is a common and serious food allergy and its prevalence has increased in the past decade. Although there is strong evidence of inheritance, the genetic causes of this disease are not well understood. Previously, a large-scale genome-wide association study described an association between human leukocyte antigen (HLA)-DQB1 and asthma; the aim of this study was to evaluate the association between HLA-DQB1 and PA. Genotypic and allelic profiles were established for 311 Caucasian members of a well-described Canadian group of children with PA and 226 Caucasian controls. Firth’s logistic regression analyses showed associations between HLA-DQB1 alleles and PA for DQB1*02 (P=1.1 × 10−8, odds ratio (OR)=0.09 (CI=0.03–0.23)) and DQB1*06:03P alleles (P=2.1 × 10−2, OR=2.82 (CI=1.48–5.45)). This study of HLA in PA demonstrates specific association between two allelic groups of the HLA-DQB1 gene (DQB1*02 and DQB1*06:03P) and PA, highlighting its possible role in the development of this disease.

Histopathology of actinic prurigo.

Actinic prurigo (AP) is an idiopathic familial photodermatosis seen in American Indians. We report on 17 patients: 16 had dermatitis and one had actinic cheilitis. Ten patients had acute dermatitis and six had chronic dermatitis. The histologies of acute AP and polymorphous light eruption (PLE: limited concept) are eczematous and indistinguishable. Both show spongiosis, superficial (and sometimes deep) perivascular lymphocytic infiltrates, and papillary dermal edema. Both also show vacuolar degeneration of the basal layer. In contrast, the chronic lichenified AP lesions are associated with marked hyper-keratosis, acanthosis, elongation of the rete ridges, and tissue repair. The large lymphoid germinal centers in the lamina propria are the main features of the lip histology. Seven biopsies were positive in the basal membrane zone on direct immunofluorescent testing, four were negative, and one was inconclusive. IgM was present in six and C3 in two. These immunofluorescent results are probably not significant. Immunofluorescent testing of the lip was negative. Although it is not possible to distinguish acute AP from PLE histologically, it is possible to differentiate the two conditions when chronic AP changes are present.

Compliance with Self-Examination Surveillance in Patients with Melanoma and Atypical Moles: An Anonymous Questionnaire Study

Background: Regular skin self-examination is suggested as a means to detect melanomas at an early stage and thus improve prognosis. Compliance, however, has seldom been assessed in a routine clinical setting and anonymously. Objectives: To assess compliance with self-examination in patients with either a previous melanoma or atypical moles (dysplastic nevi) and to examine the perceived utility of supplied photographs. Methods: An anonymous questionnaire was sent to all patients seen with either a melanoma or atypical moles between the years 1995 and 2005. The melanoma cohort consisted of 143 patients. There were 440 patients with atypical moles. Results: Replies to the questionnaire were received from 94 of the melanoma patients and from 185 patients in the atypical mole cohort. Only 22% (12) in the melanoma group performed a total skin examination monthly. Fewer than 10% of those with atypical moles did a monthly skin examination, but about half of the patients examined their entire skin more than once a year. Conclusion: Self-examination is practiced in the majority of patients with either a previous melanoma or atypical moles. Those doing this on a regular monthly basis are a small minority.

Major gene segregation of actinic prurigo among north American Indians in Saskatchewan

Actinic prurigo is an idiopathic, familial photodermatosis seen especially in American Indians. Segregation analysis was performed on 12 Saskatchewan pedigrees with American Indian ancestry, comprising a total of 1,148 individuals, ascertained via probands diagnosed with actinic prurigo. Although a high degree of familial aggregation has been noted in the past and dominant inheritance has been suggested, no formal segregation analysis has been attempted. Actinic prurigo has a variable age of onset and, therefore, age at the time of censoring must be taken into account in the analysis. However, as these ages of 57% of the unaffected individuals were missing, an algorithm was devised to impute the missing ages from known birth years in the family based on the age differences among relatives and spouses. Using these imputed ages, simple dominant inheritance with incomplete penetrance and a single age of onset distribution was found. The method for imputing the ages at examination was evaluated, as was the correction for ascertainment, by using alternative methods and comparing the results. Regardless of the method used, a dominant mode of inheritance without any multifactorial component remained the best hypothesis.