Sebum excretion rates in mothers and neonates

The Global Prevalence of Seborrheic Dermatitis: A Systematic Review and Meta-Analysis

Importance

Seborrheic dermatitis is a prevalent chronic inflammatory skin disease, yet its global prevalence, pathogenesis, and epidemiology remain inadequately defined.

Objective

To provide a detailed estimation of the global prevalence of seborrheic dermatitis, analyze demographic variations, and explore differences in various settings.

Data Sources

Embase, PubMed, Scopus, and Cochrane Database of Systematic Reviews were searched from inception through October 2023.

Study Selection

Original investigations on seborrheic dermatitis prevalence were included after duplicate screening of titles, abstracts, and full articles, including only studies with clinician-diagnosed cases.

Data Extraction and Synthesis

Following PRISMA guidelines, data were extracted and quality was assessed independently by multiple reviewers. A random-effects model using restricted maximum likelihood was used for meta-analysis and subgroup analyses.

Main Outcome and Measure

The primary outcome was the pooled estimate of global seborrheic dermatitis prevalence.

Results

From 1574 identified articles, 121 studies were included, encompassing 1 260 163 individuals and revealing a pooled global seborrheic dermatitis prevalence of 4.38% (95% CI, 3.58%-5.17%), with significant heterogeneity (I2 = 99.94%). Subgroup analyses showed variations by age, with a higher prevalence in adults (5.64% [95% CI, 4.01%-7.27%]) compared to children (3.70% [95% CI, 2.69%-4.80%]) and neonates (0.23% [95% CI, 0.04%-0.43%]). Geographic analyses indicated variability, with the highest prevalence in South Africa (8.82% [95% CI, 3.00%-14.64%]) and the lowest in India (2.62% [95% CI, 1.33%-3.92%]).

Conclusions and Relevance

This comprehensive meta-analysis provides a detailed estimation of the global prevalence of seborrheic dermatitis, highlighting significant variability across different demographics and settings.

Pediatric Acne Vulgaris: A Guide for Recognition, Examination, Referral, and Treatment

Acne is a common skin condition in adolescent patients but much less common in childhood. Pediatric providers should be familiar with the varying presentations in the pediatric population and recognize when additional physical signs of hyperandrogenism are present. This article details the pathogenesis and presentation of acne in infancy, mid-childhood, and preadolescence. The differential diagnosis is discussed and recommendations for initial workup, referral, and treatment are provided. [Pediatr Ann. 2024;53(4):e115-e120.].

Association between skin barrier development and early-onset atopic dermatitis: A longitudinal birth cohort study

BACKGROUND

A diagnosis of atopic dermatitis (AD) is common during infancy; however, it is unclear whether differential skin barrier development defines this period and signals disease onset in predisposed individuals.

OBJECTIVE

We sought to study (NCT03143504) and assess the feasibility of remote skin testing from birth to monitor skin barrier maturation and model association with an AD diagnosis by age 12 months.

METHODS

Biophysical testing and infrared spectroscopy were conducted at the maternity ward and family home. Tape stripping collected samples for desquamatory protease and natural moisturizing factor analysis. The 4 common European filaggrin risk alleles were screened.

RESULTS

A total of 128 infants completed the study, with 20% developing mild disease. Significant changes in permeability barrier function, desquamatory protease activity, and molecular composition assessed spectroscopically were observed longitudinally, but only subtle evidence of differential skin barrier development was noted between infant subgroups. Common filaggrin risk alleles were strongly associated with early-onset disease and conferred a significant reduction in natural moisturizing factor and water content by age 4 weeks. Accounting for a family history of atopy, these parameters alongside a greater lipid/protein ratio and reduced chymotrypsin-like activity at birth were associated with AD. Measured in ambient conditions, transepidermal water loss did not signal disease risk at any stage.

CONCLUSIONS

Skin barrier dysfunction lacked an acquired modality but was considered proportional to cohort severity and suggests that a portfolio of tests used in a community setting has the potential to improve current AD risk evaluations from birth.

How do the skin barrier and microbiome adapt to the extra-uterine environment after birth? Implications for the clinical practice

The multiple protective functions of the skin derive from the interactions between epithelial skin and immune cells as well as the commensal microbiota. Developed in the last trimester of intra-uterine life, the skin barrier adapts dynamically after birth. Specific differences in the structure and physiology have been disclosed between infant and adult skin. The stratum corneum of infants is thinner and structured by thicker corneocytes with a more anisotropic surface in comparison to adult skin. Lower levels of the natural moisturizing factor and its constituents, together with the increased protease activity in the epidermis result in dry baby skin and ongoing adaptation of the desquamation to the extra-uterine environment. Infant epidermis is characterized by an accelerated proliferation rate and clinically competent permeability barrier in term neonates, despite the higher baseline values of transepidermal water loss in infants. The skin surface of newborns is less acidic, which could increase susceptibility to diaper and atopic dermatitis. Immediately after birth, skin is colonized by commensal bacteria-a process dependent on the mode of delivery and of major importance for the maturation of the immune system. Skin bacterial diversity and dysbiosis have been related to different pathology such as atopic and seborrheic dermatitis. This paper focuses on the ongoing structural, functional and biochemical adaptation of the human skin barrier after birth. We discuss the interactions on the 'skin barrier/ microbiota/ immune system' axis and their role in the development of competent functional integrity of the epidermal barrier.

Newborn and elderly skin: two fragile skins at higher risk of pressure injury

Skin is a key organ maintaining internal homeostasis by performing many functions such as water loss prevention, body temperature regulation and protection from noxious substance absorption, microorganism intrusion and physical trauma. Skin ageing has been well studied and it is well known that physiological changes in the elderly result in higher skin fragility favouring the onset of skin diseases. For example, prolonged and/or high-intensity pressure may suppress local blood flow more easily, disturbing cell metabolism and inducing pressure injury (PI) formation. Pressure injuries (PIs) represent a significant problem worldwide and their prevalence remains too high. A higher PI prevalence is correlated with an elderly population. Newborn skin evolution has been less studied, but some data also report a higher PI prevalence in this population compared to older children, and several authors also consider this skin as physiologically fragile. In this review, we compare the characteristics of newborn and elderly skin in order to determine common features that may explain their fragility, especially regarding PI risk. We show that, despite differences in appearance, they share many common features leading to higher fragility to shear and pressure forces, not only at the structural level but also at the cellular and molecular level and in terms of physiology. Both newborn and elderly skin have: (i) a thinner epidermis; (ii) a thinner dermis containing a less-resistant collagen network, a higher collagen III:collagen I ratio and less elastin; (iii) a flatter dermal-epidermal junction (DEJ) with lower anchoring systems; and (iv) a thinner hypodermis, resulting in lower mechanical resistance to skin damage when pressure or shear forces are applied. At the molecular level, reduced expression of transforming growth factor β (TGFβ) and its receptor TGFβ receptor II (TβRII) is involved in the decreased production and/or increased degradation of various dermal extracellular matrix (ECM) components. Epidermal fragility also involves a higher skin pH which decreases the activity of key enzymes inducing ceramide deficiency and reduced barrier protection. This seems to be correlated with higher PI prevalence in some situations. Some data also suggest that stratum corneum (SC) dryness, which may disturb cell metabolism, also increases the risk of PI formation. Besides this structural fragility, several skin functions are also less efficient. Low applied pressures induce skin vessel vasodilation via a mechanism called pressure-induced vasodilation (PIV). Individuals lacking a normal PIV response show an early decrease in cutaneous blood flow in response to the application of very low pressures, reflecting vascular fragility of the skin that increases the risk of ulceration. Due to changes in endothelial function, skin PIV ability decreases during skin ageing, putting it at higher risk of PI formation. In newborns, some data lead us to hypothesize that the nitric oxide (NO) pathway is not fully functional at birth, which may partly explain the higher risk of PI formation in newborns. In the elderly, a lower PIV ability results from impaired functionality of skin innervation, in particular that of C-fibres which are involved in both touch and pain sensation and the PIV mechanism. In newborns, skin sensitivity differs from adults due to nerve system immaturity, but the role of this in PIV remains to be determined.

Skin Barrier Function in Infants: Update and Outlook

A good understanding of infant skin should provide a rationale for optimum management of the health of this integument. In this review, we discuss the skin barrier function of infants, particularly with reference to the use of diapers and baby wipes. The skin barrier of newborns continues to develop with age. Two years after birth, the barrier properties of infant skin closely resemble those of adult skin. However, several risk factors may contribute to impaired skin barrier and altered skin permeability in infants. Problems may arise from the use of diapers and baby wipes. The skin covered by a diaper is effectively an occluded environment, and thus is vulnerable to over-hydration. To date there has been no published information regarding dermal absorption of ingredients contained in baby wipes. Similarly, dermal absorption of topical ingredients in infants with underlying skin conditions has not been widely explored. Clearly, there are serious ethical concerns related to conducting skin permeation studies on infant skin. However, the increasing availability of non-invasive methods for in vivo studies is encouraging and offers new directions for studying this important patient group.

Neuroendocrinology and neurobiology of sebaceous glands

The nervous system communicates with peripheral tissues through nerve fibres and the systemic release of hypothalamic and pituitary neurohormones. Communication between the nervous system and the largest human organ, skin, has traditionally received little attention. In particular, the neuro-regulation of sebaceous glands (SGs), a major skin appendage, is rarely considered. Yet, it is clear that the SG is under stringent pituitary control, and forms a fascinating, clinically relevant peripheral target organ in which to study the neuroendocrine and neural regulation of epithelia. Sebum, the major secretory product of the SG, is composed of a complex mixture of lipids resulting from the holocrine secretion of specialised epithelial cells (sebocytes). It is indicative of a role of the neuroendocrine system in SG function that excess circulating levels of growth hormone, thyroxine or prolactin result in increased sebum production (seborrhoea). Conversely, growth hormone deficiency, hypothyroidism, and adrenal insufficiency result in reduced sebum production and dry skin. Furthermore, the androgen sensitivity of SGs appears to be under neuroendocrine control, as hypophysectomy (removal of the pituitary) renders SGs largely insensitive to stimulation by testosterone, which is crucial for maintaining SG homeostasis. However, several neurohormones, such as adrenocorticotropic hormone and α-melanocyte-stimulating hormone, can stimulate sebum production independently of either the testes or the adrenal glands, further underscoring the importance of neuroendocrine control in SG biology. Moreover, sebocytes synthesise several neurohormones and express their receptors, suggestive of the presence of neuro-autocrine mechanisms of sebocyte modulation. Aside from the neuroendocrine system, it is conceivable that secretion of neuropeptides and neurotransmitters from cutaneous nerve endings may also act on sebocytes or their progenitors, given that the skin is richly innervated. However, to date, the neural controls of SG development and function remain poorly investigated and incompletely understood. Botulinum toxin-mediated or facial paresis-associated reduction of human sebum secretion suggests that cutaneous nerve-derived substances modulate lipid and inflammatory cytokine synthesis by sebocytes, possibly implicating the nervous system in acne pathogenesis. Additionally, evidence suggests that cutaneous denervation in mice alters the expression of key regulators of SG homeostasis. In this review, we examine the current evidence regarding neuroendocrine and neurobiological regulation of human SG function in physiology and pathology. We further call attention to this line of research as an instructive model for probing and therapeutically manipulating the mechanistic links between the nervous system and mammalian skin.

Layton A. A novel method to demonstrate that pregnant women with polycystic ovary syndrome hyper-expose their fetus to androgens as a possible stepping stone for the developmental theory of PCOS. A pilot study

BACKGROUND

Polycystic ovary syndrome (PCOS), whose aetiology is unknown, is predominately a familial syndrome but confirmation of candidate genes has proved elusive. The developmental hypothesis for the origin of PCOS suggests that exposure of the fetus to excess androgens influences imprinting, leading to altered genetic expression in adult life. The aim of this pilot study was to examine whether the female fetus of a mother with PCOS is indeed exposed to excess androgens.

METHODS

Using sebum production in the newborn as a surrogate for exposure to excess androgens during pregnancy thisprospective case control studyexamined whether neonatal sebum excretion is greater in female infants born to PCOS mothers compared to non-PCOS. Women with known PCOS (all 3 Rotterdam criteria) (n = 9) and non-PCOS controls (n = 12), with a female fetus, were recruited at 24 weeks pregnancy and serum testosterone estimated. Sebum was measured using Sebutape® for 30 and 60 min within 24 h of birth, at 1 week, 4-6 weeks and 6 months after birth in both mother and child. Sebum excretion was measured in mother and child in the same site at each time frame and consistently. All semi-quantitative sebum excretion estimations were compared (t-test) between the two groups and correlated with testosterone concentrations during pregnancy.

RESULTS

In this pilot study, 21 women completed the 6 month examination period (PCOS group (n = 9) and controls (n = 12). Mean testosterone was 6.2 nmol/L (normal <3.1 nmol/L) in PCOS mothers and 2.75 nmol/L in controls at 24 weeks pregnancy. At all time frames, the results of sebum excretion at 30 and 60 min were consistent. The sebum excretion of mothers in both groups was fairly constant from birth throughout 6 months. All babies were born between 37 and 41 weeks gestational age. Six of nine newborns had detectable sebum excretion at birth in the PCOS mothers group compared to 1 of 12 in the controls (P = 0.01).

CONCLUSIONS

These results suggest that women with PCOS could hyper-expose their fetus to androgens in-utero and that this may be detected using a simple novel test within 24 h of birth to predict development of PCOS in adult life and induce research to eliminate its symptoms.

TRIAL REGISTRATION

NCT 02654548 .Clinical Trials UK.Retrospectively registered 11/1/16.

Development of stratum corneum chymotrypsin-like protease activity and natural moisturizing factors from birth to 4 weeks of age compared with adults

BACKGROUND

From birth, the functional properties of the neonatal epidermal barrier mature whereby the stratum corneum (SC) hydrates and the skin surface acidifies. The identification of a thinner infant SC compared with adults suggests underdeveloped mechanisms underlying differentiation and desquamation.

OBJECTIVES

To assess the functional properties of the neonatal SC from birth, in conjunction with the quantification of superficial chymotrypsin-like protease activity [kallikrein-7 (KLK-7)] and filaggrin-derived natural moisturizing factors (NMF).

METHODS

A total of 115 neonates recruited to the Oil in Baby SkincaRE (OBSeRvE) randomized controlled trial underwent a full evaluation of the SC at birth (< 72 h old) and at 4 weeks of age (n = 39, no oil control group) using minimally invasive instrumentation and methodology. A cohort of 20 unrelated adults was recruited for comparison.

RESULTS

At birth NMF levels correlated with SC hydration (r = 0·50) and skin-surface pH (r = -0·54). From birth to 4 weeks, transepidermal water loss (TEWL), superficial KLK-7 activity and filaggrin-derived NMF significantly elevated. Impaired epidermal barrier function at birth (> 75th percentile TEWL) was accompanied by significantly elevated chymotrypsin-like protease activity and reduced levels of NMF.

CONCLUSIONS

The biophysical, biological and functional properties of the developing neonatal SC are transitional from birth to 4 weeks of age and differ significantly from adults. The presence of impaired barrier function with elevated protease activity and reduced NMF at birth suggests why certain infants are predisposed to epidermal barrier breakdown and the development of atopic dermatitis.

Investigation of the Association of the Second-to-Fourth Digit Ratio with Skin Sebum Levels in Females with Acne Vulgaris

BACKGROUND

A relationship between acne vulgaris (AV) and the masculinized (lower) second-to-fourth digit (2D:4D) ratio in females was demonstrated in our previous study. Development of the digits and the sebaceous glands both occur during the same gestational period; therefore, the association between the 2D:4D ratios and AV may result from the effects of the prenatal endocrine environment on the sebaceous glands.

OBJECTIVE

The aim of this study was to evaluate the relationship between the 2D:4D ratio and sebum levels in the skin of females with AV.

METHODS

In total, 215 female AV patients and 92 healthy controls, aged 18-35 years, were enrolled in this study. Finger-length measurements were made using a digital Vernier caliper, and the sebum levels of five facial areas were measured using a Sebumeter SM 815. Acne severity was assessed using the International Consensus Conference on Acne Classification System.

RESULTS

The 2D:4D ratios of the AV patients were significantly lower than those of the controls, for both hands. The mean sebum levels in the T-zone, U-zone and whole face were significantly higher for AV patients compared with controls. The 2D:4D ratio in the left hand showed significant negative correlations with the sebum levels in the U-zone; however, no association was found between the 2D:4D ratios and sebum levels in the T-zone and whole face. While acne severity was positively correlated with skin sebum levels, no correlation between acne severity and 2D:4D ratios was observed.

CONCLUSION

This study provides preliminary evidence regarding the association between lower 2D:4D ratios and higher rates of sebum secretion in the U-zone for females with AV. The 2D:4D ratio might be a predictor of sebum levels, as well as acne development, in females.

Postnatal maturation of skin barrier function in premature infants

BACKGROUND

In preterm infants, skin barrier maturation entails regional variability.

OBJECTIVES

To characterize postnatal skin barrier development in covered, uncovered and diapered regions in healthy premature infants over a longitudinal observation period.

METHODS

Transepidermal water loss (TEWL), stratum corneum hydration (SCH), pH and sebum were measured at postnatal ages of 1-7 days and 2-7 weeks on the forehead, abdomen, thigh and buttock of preterm infants (gestational age 30-37 weeks; n = 48) under monitored ambient conditions. A standard minimal skin care regimen was practised.

RESULTS

TEWL increased significantly on the buttock (p = 0.007), while remaining stable on the forehead, abdomen and thigh. SCH and sebum remained stable in all studied body regions with increasing age. On the buttock, pH increased (p = 0.049), while other body regions exhibited a significant decrease (p ≤ 0.019). TEWL (p < 0.001) and SCH (p ≤ 0.002) revealed significantly higher values on the buttock, compared to other body regions.

CONCLUSIONS

Stable TEWL, SCH and sebum values may indicate a lack of skin barrier maturation. Postnatal decrease in skin pH suggests an adaptation process with acid mantle formation. Differences in skin barrier development were observed between anatomical regions. SCH, TEWL and pH values demonstrated a distinct course in the diaper area, indicating an impaired skin barrier function in this region.

The role of the skin barrier in modulating the effects of common skin microbial species on the inflammation, differentiation and proliferation status of epidermal keratinocytes

Background

Skin resident microbial species are often thought of either as pathogenic or commensal. However, little is known about the role of the skin barrier in modulating their potential for causing disease. To investigate this question we measured the effects of three microbial species commonly found on the skin (Staphylococcus epidermidis, Staphylococcus aureus, and Propionibacterium acnes) on a reconstructed human epidermal model by either applying the bacteria on the model surface (intact barrier) or adding them to the culture medium (simulating barrier breach).

Results

When added to the medium, all of the tested species induced inflammatory responses and keratinocyte cell death with species-specific potency. P. acnes and S. epidermidis induced specific alterations in the expression of keratinocyte differentiation and proliferation markers, suggesting a barrier reparation response. S. aureus induced complete keratinocyte cell death. On the contrary, topically applied S. epidermidis and P. acnes caused no inflammatory response even when tested at high concentrations, while topical S. aureus induced a weak reaction. None of the tested species were able to alter the expression of keratinocyte differentiation or expression markers, when applied topically.

Conclusions

We show that the skin barrier prevents the effects of common skin bacteria on epidermal keratinocyte inflammation, differentiation and proliferation and highlight the importance of skin barrier in defending against the pathogenic effects of common skin bacteria.

Diversity of the human skin microbiome early in life

Within days after birth, rapid surface colonization of infant skin coincides with significant functional changes. Gradual maturation of skin function, structure, and composition continues throughout the first years of life. Recent reports have revealed topographical and temporal variations in the adult skin microbiome. Here we address the question of how the human skin microbiome develops early in life. We show that the composition of cutaneous microbial communities evolves over the first year of life, showing increasing diversity with age. Although early colonization is dominated by Staphylococci, their significant decline contributes to increased population evenness by the end of the first year. Similar to what has been shown in adults, the composition of infant skin microflora appears to be site specific. In contrast to adults, we find that Firmicutes predominate on infant skin. Timely and proper establishment of healthy skin microbiome during this early period might have a pivotal role in denying access to potentially infectious microbes and could affect microbiome composition and stability extending into adulthood. Bacterial communities contribute to the establishment of cutaneous homeostasis and modulate inflammatory responses. Early microbial colonization is therefore expected to critically affect the development of the skin immune function.

[The sebaceous gland]

The development and function of the sebaceous gland in the fetal and neonatal periods appear to be regulated by maternal androgens and by endogenous steroid synthesis, as well as by other morphogens. The most apparent function of the glands is to excrete sebum. A strong increase in sebum excretion occurs a few hours after birth; this peaks during the first week and slowly subsides thereafter. A new rise takes place at about age 9 years with adrenarche and continues up to age 17 years, when the adult level is reached. The sebaceous gland is a target organ but also an important formation site of hormones, and especially of active androgens. Hormonal activity is based on an hormone (ligand)-receptor interaction, whereas sebocytes express a wide spectrum of hormone receptors. Androgens are well known for their effects on sebum excretion, whereas terminal sebocyte differentiation is assisted by peroxisome proliferator-activated receptor ligands. Estrogens, glucocorticoids, and prolactin also influence sebaceous gland function. In addition, stress-sensing cutaneous signals lead to the production and release of corticotrophin-releasing hormone from dermal nerves and sebocytes with subsequent dose-dependent regulation of sebaceous nonpolar lipids. Among other lipid fractions, sebaceous glands have been shown to synthesize considerable amounts of free fatty acids without exogenous influence. Atopic dermatitis, seborrheic dermatitis, psoriasis and acne vulgaris are some of the disease on which pathogenesis and severity sebaceous lipids may or are surely involved.

Functional skin adaptation in infancy - almost complete but not fully competent

Early postnatal life is a period of active functional reorganization and cutaneous physiological adaptation to the extrauterine environment. Skin as the outermost organ of mammalians is endowed of multiple functions such as protection, secretion, absorption and thermoregulation. Birth stimulates the epidermal barrier maturation and the skin surface acidification especially in premature infants. In full-term infants the developed stratum corneum accomplishes competent barrier function, in contrast to prematures. Complete barrier maturation in preterm infants is fulfilled by 2-4 weeks of the postnatal life. However, in preterms with 23-25 weeks gestational age this process takes longer. Versatile regulatory mechanisms, namely skin surface acidity, calcium ion gradient and nuclear hormone receptors/ligands are interrelated in the complex postnatal newborn adaptation. The skin of newborns is adjusting quickly to the challenging environmental conditions of the postpartum. However, certain functions, for example, microcirculation, continue to develop even beyond the neonatal period, that is, up to the age of 14-17 weeks. Different environmental factors (for instance, dry and cold climate, diapers and cosmetic care procedures) influence the postnatal development of skin functional parameters such as stratum corneum hydration and the permeability barrier especially in premature infants. The aim of this article is to summarize the current knowledge on skin physiology in newborn and infants with a practical approach and to discuss the possible clinical consequences. This review offers the readership a critical and practical overview of skin physiology in newborns and infants. It emphasizes possible new research fields in neonatal and infantile skin physiology.

Clinical and therapeutic approach to childhood acne: an update

There is a limited literature reporting on acne in childhood. Childhood acne can be classified in neonatal, infantile, mid-childhood, and prepubertal acne, depending on the age of onset. In this review we will present an update on the clinical approach and therapeutic options when facing prepubertal acne in a child. The use of tetracyclines is contraindicated in children younger than 8 years, and oral isotretinoin is not recommended in children younger than 12 years of age according to the FDA and the European Commission. Nevertheless, there are case reports of 10 patients successfully treated with oral isotretinoin for recalcitrant infantile acne with scarring. Further studies are needed to investigate whether isotretinoin may improve the long-term prognosis of infantile acne, which may be associated with more severe acne in adolescence.

Skin care of the diaper area

The skin of the diaper area has special needs for protection from the irritating effects of urine and feces and prevention of diaper dermatitis. These needs include products such as diapers that absorb the excreta, as well as products for cleansing and conditioning the skin. A number of factors play a role in development of diaper dermatitis, including prolonged exposure to excreta, alterations in skin pH or increased hydration, and changes in skin microbial flora. Recent decades have seen great improvements in our understanding of these factors and our ability to develop new and better products to protect baby skin. Better diaper designs and the development of pH-buffered baby wipes have improved the care of skin in the diaper area. Continuing research offers the promise of new products with additional benefits for caregivers and infants.

Prevalence of pityriasis versicolor in a group of Italian pregnant women

BACKGROUND

Although a predisposing role of pregnancy to Malassezia infections is referred, data on the prevalence of pityriasis versicolor (PV) in pregnant women are not available in literature.

OBJECTIVE

To investigate the frequency of PV during pregnancy, 60 pregnant women were clinically and microscopically investigated during and after pregnancy.

RESULTS

Fifty-two women completed all visits; three women were affected by PV at first or third trimester of pregnancy, and none at 6 months after delivery. Colonization due to Malassezia yeasts was very significantly (P < 0.01) or significantly increased (P < 0.05) at the third trimester and 6 months after delivery, respectively. No variation was observed between the end of pregnancy and the postpartum (P > 0.05).

CONCLUSION

Frequency of PV during pregnancy (5.7%) does not seem different from that reported in general population living in temperate climates (2-5%). However, higher degree of colonization by Malassezia resulted at the end of pregnancy and postpartum.

Relationship between sebostatic activity, tolerability and efficacy of three topical drugs to treat mild to moderate acne

BACKGROUND

Acne is a multifactorial disorder in which the sebum plays an important pathogenetic role.

PURPOSE OF THE STUDY

To evaluate the sebostatic effect of three anti-acneic ingredients (azelaic acid, adapalene and benzoyl peroxide) conveyed in cream and to determine whether there is a correlation with the therapeutic results.

MATERIALS AND METHODS

Sixty-five patients with mild or moderate acne localized on the face were divided into three therapy groups at random: 25 applied azelaic acid once a day, 20, benzoyl peroxide and 20, adapalene. All the patients were observed at the time of enrolling and a further four times at fortnightly intervals. At each visit the sebum casual level on the forehead, chin and one cheek was measured using a sebumeter. Furthermore, side-effects and clinical-therapeutic effectiveness were noted.

RESULTS

Four patients did not complete the study. Azelaic acid showed an average reduction of 13.9% in sebum production on the forehead, 14.2% on the chin and 15.2% on the cheek. Benzoyl peroxide caused an increase of 10.5% in sebum production on the forehead, 10.3% on the chin and 25.4% on the cheek. Adapalene reduced sebaceous secretion by 0.2% on the forehead and 6.7% on the cheek whereas sebum production increased by 6.2% on the chin. All three drugs showed a clinical improvement in the acneic lesions with moderate adverse effects.

CONCLUSION

The three topical drugs bring about good therapeutic results with scarce side-effects that do not, however, seem to be correlated with the sebostatic activity.

Oral and vulvar changes in pregnancy

The endocrinologic, immunological, and vascular changes that occur during pregnancy are far-reaching. These systemic factors produce profound local impact on the physiology and pathology of the oral cavity, vagina, and vulva. Physiological changes can be expected and tolerable or of such severity that they are viewed as pathological. Existing disease can be exacerbated and dermatoses specific to pregnancy can erupt. Each of these conditions can pose potentially challenging treatment considerations.

Histology of the pouch epithelium and the mammary glands during chemically induced oestrus in the brushtail possum (Trichosurus vulpecula)

Changes in the epithelium of the maternal pouch and the mammary gland of brushtail possums (Trichosurus vulpecula) were examined after animals were treated to induce ovulation with follicle-stimulating hormone (FSH), luteinizing hormone (LH), pregnant mares' serum gonadotrophin (PMSG) and oestradiol. The mammary glands were similar in appearance to those described in eutherian mammals and in previous studies on other marsupials. Exposure of possums to these compounds, particularly PMSG, appeared to result in changes in the mammary glands that could be associated with milk/secretion production. In contrast, the pouch epithelium had a similar histological appearance to that of epithelium from other parts of the body regardless of whether the animal was exposed to stimulants. These preliminary observations are discussed in the context of the purported role of the pouch epithelium and the mammary gland in production of secretions at oestrus and provision of immunological protection to the neonatal marsupial.

Stratum corneum maturation. A review of neonatal skin function

The importance of the stratum corneum and its barrier function for infants, especially for newborns, is clinically evident. Research regarding the maturation of the stratum corneum in neonates, i.e. when full barrier function is obtained, has produced varying results. Based on transepidermal water loss and percutaneous absorption studies, term infants seem to possess stratum corneum with adult barrier properties. Additionally, postnatal life is thought to accelerate stratum corneum maturation, so that even preterm infants have barrier function similar to term infants at 2-3 weeks of gestational age. However, a look at other parameters, such as skin thickness, skin pH and stratum corneum hydration, shows that neonatal skin is always adjusting to the extrauterine environment in contrast to the steady state of adult skin. This suggests that barrier stabilization may be dependent on achieving a balance between different parameters. However, it is still in question, which parameters, what balance and what timing. This paper provides an up-to-date overview on the neonatal skin barrier based on the review of current literature.

Acne and sebaceous gland function

The embryologic development of the human sebaceous gland is closely related to the differentiation of the hair follicle and the epidermis. The number of sebaceous glands remains approximately the same throughout life, whereas their size tends to increase with age. The development and function of the sebaceous gland in the fetal and neonatal periods appear to be regulated by maternal androgens and by endogenous steroid synthesis, as well as by other morphogens. The most apparent function of the glands is to excrete sebum. A strong increase in sebum excretion occurs a few hours after birth; this peaks during the first week and slowly subsides thereafter. A new rise takes place at about age 9 years with adrenarche and continues up to age 17 years, when the adult level is reached. The sebaceous gland is an important formation site of active androgens. Androgens are well known for their effects on sebum excretion, whereas terminal sebocyte differentiation is assisted by peroxisome proliferator-activated receptor ligands. Estrogens, glucocorticoids, and prolactin also influence sebaceous gland function. In addition, stress-sensing cutaneous signals lead to the production and release of corticotrophin-releasing hormone from dermal nerves and sebocytes with subsequent dose-dependent regulation of sebaceous nonpolar lipids. Among other lipid fractions, sebaceous glands have been shown to synthesize considerable amounts of free fatty acids without exogenous influence. Sebaceous lipids are responsible for the three-dimensional skin surface lipid organization. Contributing to the integrity of the skin barrier. They also exhibit strong innate antimicrobial activity, transport antioxidants to the skin surface, and express proinflammatory and anti-inflammatory properties. Acne in childhood has been suggested to be strongly associated with the development of severe acne during adolescence. Increased sebum excretion is a major factor in the pathophysiology of acne vulgaris. Other sebaceous gland functions are also associated with the development of acne, including sebaceous proinflammatory lipids; different cytokines produced locally; periglandular peptides and neuropeptides, such as corticotrophin-releasing hormone, which is produced by sebocytes; and substance P, which is expressed in the nerve endings at the vicinity of healthy-looking glands of acne patients. Current data indicate that acne vulgaris may be a primary inflammatory disease. Future drugs developed to treat acne not only should reduce sebum production and Propionibacterium acnes populations, but also should be targeted to reduce proinflammatory lipids in sebum, down-regulate proinflammatory signals in the pilosebaceous unit, and inhibit leukotriene B(4)-induced accumulation of inflammatory cells. They should also influence peroxisome proliferator-activated receptor regulation. Isotretinoin is still the most active available drug for the treatment of severe acne.

Seborrheic dermatitis

Seborrheic dermatitis is a common inflammation of the skin, occurring most often on the face, scalp and chest. It is closely related to infantile seborrheic dermatitis, or diaper rash. Seborrheic dermatitis is particularly common in patients with Parkinson's disease or with HIV/AIDS. The recent resurgence of interest in Malassezia yeasts has revived the old hypothesis that seborrheic dermatitis is caused by an altered relationship between these skin commensals and the host. Moreover, the success of antifungal medications in treating seborrheic dermatitis provides new evidence for this view.

LEARNING OBJECTIVE

Upon completing this paper, the reader should be aware of the clinical presentation of seborrheic dermatitis and which populations are at particular risk of developing this disorder. In addition, s/he will be aware of the role of Malassezia yeasts in seborrheic dermatitis and the way in which knowledge of the importance of these yeasts has altered the treatment of this disorder.

Chronological ageing and photoageing of the human sebaceous gland

The human sebaceous gland undergoes both extrinsic and intrinsic ageing. The latter is associated with morphological changes and alteration in the sebaceous gland activity. The high androgen-dependent sebum secretion in neonates falls during childhood, starts to rise again during puberty and reaches its maximum in young adults. While the number of sebaceous glands remains the same during life, sebum levels tend to decrease after menopause in females, whereas no major changes appear until the eighth decade of life in men. Reduced androgen levels in aged individuals lead to a slow cellular turnover in the sebaceous glands resulting in hyperplasia of the facial sebaceous glands in advanced age. Ultraviolet radiation and immune suppression (cyclosporin A with corticosteroids) represent cofactors for the development of sebaceous gland hyperplasia. Current molecular findings indicate that overexpression of the ageing-associated gene Smad7 and parathormone-related protein correlate with sebaceous gland hyperplasia, whereas c-myc overexpression is associated with enhanced sebum production. On the other hand, down-regulation of the mismatch repair genes hMLH-1 and hMSH-2 may promote the development of sebaceous gland carcinoma. In addition to spontaneous single tumours, sebaceous gland carcinomas have been reported in immune-suppressed transplant recipients (azathiorpine, cisplatin, cyclosporin A) and in association with the Muir-Torre syndrome. Microsatellite instability with a loss of the mismatch repair gene hMSH-2 has been detected in immune suppressed patients and under photo-induced DNA damage. Topical and systemic oestrogens offer treatment options for skin xerosis in menopausal females. A combination of isotretinoin and interferon-alpha may prevent tumour development in patients with Muir-Torre syndrome.