Resident CoRneR Neonatal Skin: A Dynamic Adaptation Process Brooke Walls, DO ecently I became an aunt, and as I held my production (eg, triglycerides, wax esters, squalene).3 precious and practically perfect niece, I con- Interestingly, sebum production increases at birth templated the fascinating and intricate post- and reaches the rate of an adult within the first week R 4 partum changes that occur in neonatal skin to adapt after birth, with good correlation between the sebum to our dry terrestrial life. During this physiologic excretion rates of neonates and their mothers.5 It is adaptation, newborns may develop a range of cutane- likely that hormonal stimuli play a role in sebaceous ous entities due to undeveloped adnexal structures, gland activity, which explains the occurrence of seba- maternal hormone stimulation, or other unknown ceous hyperplasia in neonates in the first few days of mechanisms. Rarely, cutaneous lesions may be indi- life, with subsequent resolution in the ensuing weeks. cators of underlying systemic diseases or congenital Although full-term neonatal skin is similar to syndromes. I recognized the yellowish papules across adult skin in many ways, it also demonstrates many my newborn niece’s nose as CUTISsebaceous hyperplasia, interesting differences. In full-term newborns, a phys- which prompted my curiosity to revisit the chal- iologic adaptation process begins immediately after lenging subject of pustular and acneform lesions in birth to adapt to extrauterine life.6 This process is neonates. I became acutely aware that I may be called expedited in preterm newborns, such that by 2 to on for a curbside consultation from her concerned 3 weeks after birth, the skin is comparable to a full- first-time parents and therefore sought to brush up on term newborn.1 The structure and function of the this subject. skin (eg, stratum corneum thickness, transepidermal ToDo understand the abnormal, Not one must first under- water loss,Copy pH, natural moisturizing factor [NMF]) stand the normal. Neonatal skin is dynamic, continu- continue to develop and evolve over the first few ously adapting to its new extrauterine environment years of life. and providing protection, thermoregulation, and The stratum corneum is fully formed in full-term electrolyte homeostasis both prepartum and postpar- newborns, albeit thinner than in adults; however, tum. The inside-out and outside-in barrier function of the barrier function of the skin is intact at birth.6,7 the skin is competent at birth in full-term newborns1; Transepidermal water loss is a recognized measure however, a rapid process of change and adaptation of barrier function and mirrors adults.7 The pH of ensues after birth to adapt to the dry terrestrial adult skin ranges from 4.0 to 5.5, creating an acidic environment. Full-term neonates are born with a environment known as the acid mantle, which is protective waxy covering termed the vernix caseosa, necessary to maintain bacteriological, chemical, and a hydrophobic film that covers the fetus in the third mechanical resistance.1 Interestingly, newborn skin trimester and fulfills a variety of functions, includ- is substantially more alkaline than adult skin at birth ing electrolyte transport, thermoregulation, protec- and during the first 24 hours of life.1 Over the next tion provided by antioxidants, and epidermal barrier few days to weeks, the pH continues to decrease, drop- development.2 The sebaceous glands directly contrib- ping to an approximate pH of 5.1 where it remains ute to the formation of the vernix caseosa via lipid until the second year of life when it typically normal- izes to the adult level. An alkaline pH increases the activity of serine proteases, which inhibits lamellar From Nova Southeastern University College of Osteopathic body secretion and induces inflammation. A high Medicine, Largo, Florida. pH also favors the colonization of Staphylococcus The author reports no conflict of interest. aureus and Candida albicans and provides a compelling WWW.CUTIS.COM VOLUME 92, AUGUST 2013 E1 Copyright Cutis 2013. No part of this publication may be reproduced, stored, or transmitted without the prior written permission of the Publisher. Resident Corner Differential Diagnosis of Pustules in Newborns8 Disease Description Treatment Infantile Recurrent crops of acral pustules; neutrophils in Usually resolves spontaneously acropustulosis the pustules within 2–3 years; antihistamines for pruritus Eosinophilic pustular Follicular pustules most commonly on the Topical corticosteroids and folliculitis scalp and extremities that recur in crops; antihistamines for symptomatic may occasionally be the presenting sign of relief; usually resolves sponta- hyperimmunoglobulin E syndrome neously by 3 years of age Erythema toxicum Blotchy erythema and evanescent macules, Self-limited neonatorum papules, and pustules that can present anywhere on the body, especially the forehead, face, trunk, and extremities; histology typically reveals folliculocentric eosinophils; usually occurs in the first 3–4 days of life; benign Impetigo Superficial vesicles that rupture easily; honey- Topical antibiotics colored crusting Milia Discrete white papules on face; retention cysts Usually resolves spontaneously composed of keratin; common in neonates by 3–4 weeks of life (persistent and/or widespread cases may be a manifestation of hereditary CUTIStrichodysplasia, dystrophic epidermolysis bullosa, Bazex syndrome, Rombo syndrome, oral-facial-digital syndrome, or Down syndrome) Miliaria rubra Occluded sites, especially intertriginous areas; Avoidance of excessive heat Dogreater Not incidence in the first few weeks Copyof life due and humidity; occlusive to relative immaturity of eccrine glands ointments in climates with high humidity Neonatal acne Acneform eruption thought to be due to Daily cleansing with mild stimulation of the sebaceous glands by soap and water; occasionally, maternal hormones mild keratolytics or topi- cal antibiotics Neonatal cephalic Acneform eruption associated with the Malassezia Topical antifungal agents pustulosis species; pinpoint pustules on the cheeks, chin, and forehead Sebaceous Physiologic phenomenon of yellowish papules Usually resolves spontaneously hyperplasia on the nose, chin, or cheeks; representative of in the first few weeks of life stimulation of the sebaceous glands by maternal androgens Transient neonatal Darker skin; hyperpigmentation that typically Lesions usually resolve pustular melanosis persists for months; collarettes of fine white scale spontaneously within smears of the pustules; often variable numbers 24–48 hours; hyperpigmentation of neutrophils gradually fades E2 CUTIS® WWW.CUTIS.COM Copyright Cutis 2013. No part of this publication may be reproduced, stored, or transmitted without the prior written permission of the Publisher. Resident Corner explanation for the high incidence of seborrheic der- first week following delivery. Cleansing with syndets matitis in newborns.7 The acid mantle highlights the or liquid baby cleansers seems comparable or superior importance of avoiding alkaline soaps and detergents to cleansing with water alone; these products also in the postnatal period. Neonatal skin has lower are less likely than soaps to raise the pH of the skin, water content in the stratum corneum despite high thereby causing less irritation.9 content of NMFs.7 In fact, Fluhr et al1 demonstrated Neonatal dermatoses often are daunting, espe- that NMF reaches its highest levels within the first cially given the heightened concern of new parents. 15 days of life, followed by a dramatic decline at Backed with this basic understanding of cutaneous 6 months of age and slow increase over the follow- physiologic adaptation processes and common der- ing years to adult levels but never to the immediate matoses in neonates, I now welcome any curbside postpartum level.7 Fluhr et al7 provided an extensive consultations my brother may throw my way about evaluation of the maturation of infant skin over the his baby girl. first 2 years of life compared to adult skin using in vivo evaluation of the above-mentioned properties; I REFERENCES recommend this study for a more in-depth discussion, 1. Fluhr JW, Darlenski R, Taieb A, et al. Functional skin ad- as the results are beyond the scope of this article. aptation in infancy—almost complete but not fully com- Along with dynamic physiologic adaptation of the petent [published online ahead of print March 23, 2010]. skin, neonates also have an increased susceptibility to Exp Dermatol. 2010;19:483-492. infection due to the cutting of the umbilical cord dur- 2. Rissmann R, Groenink HW, Weerheim AM, et al. New ing delivery as well as possible circumcision in males, insights into ultrastructure, lipid composition and or- which creates at least 1 and potentially 2 open surgi- ganization of vernix caseosa [published online ahead cal wounds. Newborns also are exposed to numerous of print April 20, 2006]. J Invest Dermatol. 2006;126: fomites at the hospital and at home. It is well known 1823-1833. that neonates have up to 5 times the surface area to 3. Williams ML, Hincenbergs M, Holbrook KA. Skin lipid mass ratio compared to adults and thus increased risk content during early fetal development. J Invest Dermatol. for percutaneous absorption of topical medications.8 1988;91:263-268. Many skin appendages areCUTIS not fully functional at 4. Agache P, Blanc D, Barrand C, et al. Sebum levels during birth1; therefore, miliaria rubra and sebaceous gland the first year of life.