26 - SEBORRHEIC DERMATITIS Flashcards
describe seborrheic dermatitis
Seborrheic dermatitis (SD) is clinically characterized by erythematous, scaly patches on sebaceous gland–rich sites, including scalp, face, upper trunk, and intertriginous areas.
The affected areas present as various appearances from mild pinkish and sometimes greasy scaling to solid adherent crusts. Patients with this condition complain of discomfort, with symptoms of itching and burning, and also have some serious cosmetic problems, leading to psychosocial distress that has a negative impact on their quality of life. 2 SD arises in all races and ethnic groups and has a worldwide distribution, but a higher incidence and more-severe forms are observed in AIDS patients and individuals with certain neurologic conditions, such as Parkinson disease.3
SD usually appears as a chronic and relapsing pattern in adolescents and young adults when the activity of sebaceous glands increases from hormonal effects, with the incidence increasing in patients with older than 50 years of age. 4 SD can also affect babies as young as age 2 weeks with peak incidence at 3 months of age, which is called _________
infantile seborrheic dermatitis
The overall prevalence of SD in general population is between 2.35% and 11.30%, depending on the study. 5 A male predominance is observed in all ages without any racial or regional predilection. SD is often influenced by a seasonal impact. It becomes more common and severe in the cold and dry climates, whereas it may be mitigated by sun exposure. However, several cases induced by treatment of psoralen plus ultraviolet A (PUVA) therapy have been reported
The symptoms of SD are mainly chronic, persistent, and recurrent. The red, flaking, and greasy lesions of scalp and face are easily observed, particularly on nasolabial folds (Fig. 26-2); eyebrows, upper eyelid, forehead, postauricular areas (Fig. 26-3)
external auditory canal and auricle (Fig. 26-4), with generally symmetrical distribution.
SD can appear in other sites, such as occiput and neck. When the sternal area on the chest (Fig. 26-5), upper back (Fig. 26-6), and umbilicus are involved, petaloid or arcuate lesions with fine pink scale can be seen.
In contrast, intertriginous areas, including inguinal and axillary regions, show less scale, making SD easily confusable with intertrigo. However, variations of these clinical appearances are common. Scalp involvement is more common in the male patient, in the patient with long disease duration, and in the patient with a history of acne. 1 The severity of SD varies from mild erythema and pruritus to severe, oily, thick scale with a burning or tingling sensation.
Some patients with SD also may present with Pityrosporum folliculitis and blepharitis. How does pityrosporum folliculitis manifest?
Pityrosporum folliculitis typically manifests as a diffuse papulopustular eruption with peripheral erythema on the trunk and arises more in immunocompromised patients.
How does seborrheic blepharitis manifest?
Seborrheic blepharitis usually appears as a type of anterior blepharitis, inducing flaking and scaling on the eyelids and creating uncomfortable, irritating problems.
Characterize infantile seborrheic dermatitis
The nonpruritic skin eruption generally affects the frontal or vertex areas (or both areas) of the scalp and the central areas of the face with dry, thick, adherent, and flaking scale, and may be accompanied by erythematous rash on intertriginous folds of the trunk and extremities (Fig. 26-7). The extensive involvement of the scalp, commonly called “cradle cap,” is one of the typical appearances observed in ISD. ISD normally resolves spontaneously within the first 6 to 12 months of life. Extensive and serious conditions should be differentiated from immunosuppressed status.
What is Leiner disease?
The term Leiner disease was first introduced by Carl Leiner in 1908, to describe infants with desquamative erythroderma, sparse hair, frequent loose stools, and failure to thrive. 7 Later, Miller reported other patients with similar clinical features who had generalized SD. Miller also found a lack of opsonization by the serum of the patients. 8 Since Miller’s findings it has become clear that Leiner disease is an umbrella phenotype rather than a single-disease entity, and a variety of immunologic defects have been identified. 9 Congenital or acquired deficiencies of C3, C5, and phagocytic activity results in defective opsonization of yeast and bacteria. Association of Leiner disease and Netherton syndrome was also suggested. 9 Secondary bacterial infection can bring death to a Leiner disease patient, so appropriate treatment, such as IV hydration, temperature regulation, and antibiotics, is essential. Infusion of fresh-frozen plasma or whole blood can be beneficial in supplementing the deficient factors in a hereditary form of Leiner’s disease. 8 The prognosis of Leiner disease depends on the nature of the underlying immunologic abnormality of the patients.
What is PITYRIASIS AMIANTACEA?
Asbestos-like scalp, called pityriasis amiantacea, was first described by Alibert in 1832. Pityriasis amiantacea is also called tinea asbestina, tinea amiantacea, keratosis follicularis amiantacea, and porrigo amiantacea.
Pityriasis amiantacea is an inflammatory condition of the scalp that is characterized by large plates of thick, silvering scale firmly adherent to both the scalp and hair tufts (Fig. 26-8).
This can be a localized or diffuse condition, and is attributed to diffuse hyperkeratosis and parakeratosis with follicular keratosis surrounding each hair with a sheath of corneocytes and debris. It is more common in females and it may occur at any age, often without evident causes. Alopecia, which is generally reversible but is sometimes cicatricial, is a common feature of pityriasis amiantacea. 10 Concomitant secondary bacterial infection, mostly Staphylococcus aureus, may result in scarring alopecia, so early and appropriate treatment is necessary. The most frequent skin diseases associated with pityriasis amiantacea are psoriasis (35%) and eczematous conditions like SD and atopic dermatitis (34%). Of pediatric patients with pityriasis amiantacea, lesions in 2% to 15% develop into typical psoriasis. 11 Pityriasis amiantacea may also manifest as a complication of lichen planus, lichen simplex chronicus, superficial fungal, or pyogenic infection, or as an adverse effect of molecularly targeted therapy such as vemurafenib. 12,13 In these cases, therapy should be directed toward the underlying etiology.
SD arises in more extensive and refractory patterns in up to 83% of HIV-seropositive and AIDS patients (Fig. 26-9).4 The initial clinical symptom may appear as a butterflylike rash seen in systemic lupus erythematosus. SD is associated with reduction of T-cell function, and gets worse as the CD4+ lymphocyte count decreases, making SD an indicator for evaluating the progression of AIDS
IMMUNE RESPONSE AND INFLAMMATION
The immune component may be important in the pathogenesis of SD because SD is much more common in immunosuppressed patients. The DBA/2 2C TCR transgenic mouse, which has a defect in expression of CD4+ and CD8+ cells owing to the lack of T-cell progenitor thymocytes, exhibited SD-like eruptions.15 Several studies have focused on the cellular immunity and humoral immunity in SD, but there are some controversies. One study showed a normal CD4+-toCD8+ ratio, whereas another study demonstrated a decreased CD4+-to-CD8+ ratio in 68% of patients. 16 A decrease in the number of B cells in 28% of patients and a rise of the number of natural killer cells in 48% of patients were reported. In addition, 60% of patients showed an increase in CD8+ cells and 70% of patients showed a diminished CD4+-to-CD8+ ratio. Also, it was stated that SD patients had an increased production of immunoglobulin (Ig) A and IgG antibodies in serum. 16 However, there was no change in the total amount of antibodies against Malassezia in SD, suggesting that changes to the antibodies are not likely linked with Malassezia. 17 The alteration of inflammatory cytokines in patients with SD has been demonstrated by immunohistochemical studies. The production of interleukin (IL)-1α, IL-1β, IL-4, IL-12, tumor necrosis factor-α, and interferon (IFN)-γ was increased in the lesions compared with the normal skin. 18 Significantly increased IL-1RA–to–IL-1α and IL-1RA–to–IL-8 ratios, as well as overproduction of histamine, were also shown to occur in SD when compared with healthy controls. 19 An investigation of gene expression by DNA microarrays in 15 patients with dandruff showed the reciprocal expression of induced inflammatory genes and repressed lipid metabolism genes compared with nondandruff individuals. 20 The expression of induced inflammatory genes was distinctly observed in uninvolved skin of the patients as well, indicating the presence of predisposing factors related to inflammation in patients with SD. Furthermore, inflammation induced by oxidative stress through reactive oxygen species may have a potential role in the pathogenesis of SD.
MICROBIAL EFFECTS
Malassezia, normal flora that inhabits human skin, is suggested to be important in SD. This opinion is based on the evidences that the common lesions of SD are related to the distribution of sebaceous glands where Malassezia preferentially colonizes, and that antifungal medications have therapeutic effects on SD. A decline in the number of Malassezia by use of antifungal agents corresponds with the relief of the symptoms. 4 Moreover, pityriasis versicolor and Pityrosporum folliculitis, induced by Malassezia, are commonly accompanied by SD. However, there is a lack of difference in Malassezia counts between patients with SD and healthy individuals. In addition, a mycelial form of Malassezia, a pathogenic form observed in pityriasis versicolor, has not been detected in SD. 17 These facts propose a complex causative role of Malassezia for SD. The prevalence and types of the most predominant Malassezia species found on SD lesions differ among studies, countries, or parts of body, but Malassezia globosa and Malassezia restricta are considered to be the most important of the 14 Malassezia species identified. 4,22 The complete genome sequences of M. globosa and M. restricta have been determined and these genomes encode lipase and phospholipase, making the species lipophilic or lipiddependent. 23 The primary role of these enzymes is to metabolize lipid into fatty acids to produce fungal cell walls responsible for virulence, including invasion and dissemination. 24 Not all M. globosa or M. restricta strains were found in SD, implying that there may exist specific strains capable of causing the disease. 25 Also, an increased amount of Malassezia furfur was observed in patients with SD versus healthy controls. 26 The high concentration of M. furfur can disturb protective skin barriers and induce inflammation. Malassezin, generated by M. furfur or M. restricta, can serve as agonists to aryl hydrocarbon receptor, which is involved in the differentiation of T-helper 17 cells and the mediation of contact sensitivity.
LIPID AND HOST SUSCEPTIBILITY FACTORS
Several analyses of skin surface lipids in patients with SD or dandruff have shown alterations in those irrespective of HIV status. 28 These findings were not consistent with one another, but they introduced the causative relationship between SD and the composition of skin surface lipids. Specifically, irritating free fatty acids, such as oleic acid produced by lipase of M. globosa, could mediate dandruff-like flaking in the dandruff-susceptible individuals with SD but not in nonsusceptible individuals. 29 Individual susceptibility is considered to be associated with a disrupted epidermal barrier that allows penetration of the irritating metabolites. The process for Malassezia to reach the aryl hydrocarbon receptor in the granular and spinous layers also may depend on such defective skin character. This host susceptibility factor could explain the lack of a positive correlation between the number of Malassezia and the severity of dandruff.
EPIDERMAL HYPERPROLIFERATION
Increased epidermal turnover in SD, which is also shown in psoriasis, implicates SD in a disorder of hyperproliferation, and Malassezia can be considered as one of the incidental outcomes derived from the phenomenon. SD resembles psoriasis in many aspects, both clinically and histologically, and it is sometimes difficult to differentiate the two diseases even after a skin biopsy. There are case reports that keratolytics and antiinflammatory medications were successful in the treatment of the patients with SD whose treatment with amphotericin B had failed. 30 This alteration of epidermis may be related with the increased activity of calmodulin and explains the basis of use of cytostatic medications such as azelaic acid.
Histopathologic Differences between Classic Seborrheic Dermatitis and AIDS-Associated Seborrheic Dermatitis
HIV-associated SD is histologically distinctive from the ordinary SD, showing very severe patterns such as extensive parakeratosis, leukoexocytosis, necrosis of keratinocytes, and superficial perivascular infiltrate of plasma cells (Table 26-1).
Site-Specific Differential Diagnosis of Seborrheic Dermatitis
Several diseases should be considered in the differential diagnosis of SD (Tables 26-2 and 26-3), especially as ISD is easily confused with atopic dermatitis, psoriasis, histiocytosis, and scabies; sometimes it is impossible to distinguish among these diseases in infants younger than 3 months of age. Checking family history and pruritus and taking certain laboratory tests including serum IgE levels and multiple allergen stimulation tests may give a clue to whether it is atopic dermatitis or ISD. When the skin eruption arises solely on the scalp, an involvement of frontal hair lines is a distinctive feature for scalp psoriasis. 38 Langerhans cell histiocytosis, previously called Letterer-Siwe disease has more generally purpuric lesions and tends to desquamate on the scalp and ulcerate on the folds and the mucosal areas. Severe itching that includes the palms and soles suggests scabies. Intertrigo, contact dermatitis, neonatal erythroderma, and multiple carboxylase deficiency should also be excluded in infants.39
Comparison of Infantile Seborrheic Dermatitis with Differential Diagnoses
