Hair follicle mites (Acari: Demodicidae) of man

Cutaneous neurogenic inflammation mediated by TRPV1-NGF-TRKA pathway activation in rosacea is exacerbated by the presence of Demodex mites

BACKGROUND

Rosacea is a common chronic inflammatory skin condition that is often refractory to treatment, with frequent relapses. Alterations in the skin immunological response and Demodex mite infestation are the primary aetiologic factors targeted for treatment. Transient receptor potential cation channel subfamily V member 1 (TRPV1) is a nociceptive cation channel that plays a role in cutaneous neurogenic pain and can be activated by various rosacea triggers.

OBJECTIVES

We investigated the effects of TRPV1 modulation in rosacea, focussing on Demodex mite colonization and cutaneous neurogenic inflammation.

METHODS

We examined mRNA expression levels according to Demodex population counts. An in vitro study using capsazepine as a TRPV1 antagonist was performed to assess the influence of TRPV1 in keratinocytes. A rosacea-like mouse model was generated by the injection of the 37-amino acid C-terminal cathelicidin peptide (LL37), and changes in the skin, dorsal root ganglion (DRG) and ears were examined.

RESULTS

Increased Demodex mite population counts were associated with increased expression levels of TRPV1, tropomyosin receptor kinase A (TrkA) and nerve growth factor (NGF), and these levels could be reduced by capsazepine treatment in keratinocytes. In an in vivo study, the downstream effects of TRPV1 activation were investigated in the skin, DRG and ears of the rosacea-like mouse model.

CONCLUSIONS

The findings of this study are instrumental for understanding the underlying causes of rosacea and could potentially lead to the development of new treatments targeting the NGF-TrkA-TRPV1 pathway. The identification of this pathway as a therapeutic target could represent a major breakthrough for rosacea research, potentially resulting in more effective and targeted rosacea treatments. This study contributes to an improved understanding of rosacea pathophysiology, which may lead to the development of more effective treatments in the future.

Prevalence of Demodex folliculorum and Demodex brevis in patients with blepharitis and chalazion

PURPOSE

Demodex folliculorum and Demodex brevis are common ectoparasites on skin that also can lead to blepharitis and chalazion. The aim of our study is to determine the prevalence of Demodex spp. in eyelashes of patients diagnosed with chronic blepharitis and chalazion.

METHODS

This study included 330 patients diagnosed with chronic blepharitis, 70 patients diagnosed with chalazion and 130 volunteers without any ocular problems. Patient eyelashes were examined under a light microscope at magnifications of × 40, × 100 and × 400. Demodex spp. were determined.

RESULTS

Parasite prevalence was significantly higher in blepharitis (75.5%) and chalazion groups (70%) compared to the control group (16.2%) (p < 0.001). The prevalence of D. folliculorum in the blepharitis group and D. brevis in the chalazion group was found to be significantly higher compared to other groups (p < 0.05). The average number of mites per eyelash was found to be significantly higher in patients with Demodex positive blepharitis (p = 0.001) and in chalazion patients (p = 0.047) than in the control group. It has been determined that mite positivity increases with age in blepharitis and control groups (p < 0.05). In the group with blepharitis, it was found that mite positivity was significant in the presence of symptoms (p = 0.0001) and Demodex positivity decreased as the education level of individuals increased (p = 0.039).

CONCLUSION

The results of the study show that Demodex spp infestations should be considered in chronic blepharitis and chalazion.

Investigation of the Relationship Between Ocular Demodex Colonization and the Conjunctival Flora

OBJECTIVE

This study aimed to determine whether ocular Demodex colonization leads to changes in the conjunctival flora in healthy middle-aged individuals.

METHODS

This study included 70 patients who applied to an ophthalmology clinic with a complaints of presbyopia. Two eyelash specimens from the lower eyelids of both eyes were obtained from each individual. In eyelash specimens were examined for Demodex spp. by direct wet smearing under microscopy. Conjunctival culture samples were cultivated on blood agar, eosin methylene blue and chocolate agar.

RESULTS

In the 38.5% of the individuals, Demodex spp. mites were found in the eyelashes, out of which 11.4% were Demodex brevis and 27.1% Demodex folliculorum. Bacterial growth was observed in 82.9% of the samples examined. The most frequently detected bacterium was Staphylococcus epidermidis (57%).

CONCLUSION

Although Demodex spp. infestation has been shown to be related to diseases on ocular surface of eyes such as pterygium, xerophthalmia and chalazion, we did not observe that it induces changes in ocular surface flora in healthy adults.

Which factors influence Demodex proliferation? A retrospective pilot study highlighting a possible role of subtle immune variations and sebaceous gland status

Demodex folliculorum and brevis are commensal mites that live in low densities in human pilosebaceous follicles as part of the normal adult microbiota, but that give rise to demodicosis and, possibly, rosacea, when they proliferate excessively. This proliferation is favored by various factors, including age, marked immunosuppression, sebaceous gland hyperplasia, and hypervascularization-related factors. To study possible factors influencing mite proliferation, we explored the effects of different variables on Demodex densities (Dd) in a retrospective study of two groups of subjects selected on the basis of their clinical diagnosis: Demodex+, consisting of subjects with demodicosis or with centro-facial papulopustules suggesting rosacea (n = 844, mean Dd 263.5 ± 8.9 D/cm² ), and Demodex-, consisting of subjects with other facial dermatoses or healthy facial skin (n = 200, mean Dd 2.3 ± 0.4 D/cm² ). Demodex densities were measured using two consecutive standardized skin surface biopsies (SSSB1 [superficial] and SSSB2 [deep]) taken from the same facial site on each subject. In the Demodex+ group: the SSSB1 decreased with age in women (p = 0.004), and the SSSB2 increased with age in men (p = 0.001) (the pattern was similar for SSSB1 + 2, but not statistically significant); Dds were lower in those who had received cortisone (either topically or systemically); 13 subjects (1.5%) had known immunosuppression, 62 (7.3%) had hypothyroidism, and in 20 (3.6% of the women) there was a reported link with pregnancy; 78 of the subjects (9.2%) were part of a pair from the same family or household; when associated bacterial infection was suspected, Staphylococcus epidermidis was often isolated. Our results suggest close interactions between the mite, sebaceous gland size and function, and subtle variations of immune status. Potential factors influencing Demodex proliferation should be further investigated, including hypothyroidism, pregnancy, corticosteroid administration, Staphylococcus epidermidis, contagiousity, and genetic background.

The Pathogenic Role of Demodex Mites in Rosacea: A Potential Therapeutic Target Already in Erythematotelangiectatic Rosacea?

Rosacea is a common facial dermatosis but its definition and classification are still unclear, especially in terms of its links with demodicosis. Triggers of rosacea (ultraviolet light, heat, spicy foods, alcohol, stress, microbes) are currently considered to induce a cascading innate and then adaptive immune response that gets out of control. Recent histological and biochemical studies support the concept that this inflammatory response is a continuum, already present from the onset of the disease, even when no clinical signs of inflammation are visible. The Demodex mite is beginning to be accepted as one of the triggers of this inflammatory cascade, and its proliferation as a marker of rosacea; moreover, the papulopustules of rosacea can be effectively treated with topical acaricidal agents. Demodex proliferation appears to be a continuum process in rosacea, and may not be clinically visible at the onset of the disease. Molecular studies suggest that Demodex may induce tolerogenic dendritic cells and collaborate with vascular endothelial growth factor (VEGF) to induce T cell exhaustion and favor its own proliferation. These interactions among VEGF, Demodex, and immunity need to be explored further and the nosology of rosacea adapted accordingly. However, treating early rosacea, with only clinically visible vascular symptoms, with an acaricide may decrease early inflammation, limit potential flare-ups following laser treatment, and prevent the ultimate development of the papulopustules of rosacea. The effectiveness of this approach needs to be confirmed by prospective controlled clinical trials with long-term follow-up. Currently, the evidence suggests that patients with only vascular symptoms of rosacea should be carefully examined for the presence of follicular scales as signs of Demodex overgrowth or pityriasis folliculorum so that these patients, at least, can be treated early with an acaricidal cream.

Increased Demodex Density in Patients Hospitalized for Worsening Heart Failure

Infection is an important factor leading to the exacerbation of heart failure (HF), resulting in hospitalization. Demodex species are obligatory parasites in human skin, and increased density was reported in immunocompromised patients. In this study, we aimed to investigate the Demodex density in hospitalized HF patients compared to that of healthy controls. Methods: This study included 36 HF patients and 36 age and sex-matched healthy controls. Five standardized biopsies were taken from the face of participants and assessed for Demodex by a light microscope. Results: At least one Demodex mite was detected in 20 HF patients and nine of the control group. The number of Demodex mites was significantly higher in the HF group (median 1; min. 0 and max. 10) compared to the control group (median 0; minimum. 0 and maximum. 3). Demodicidosis was positive in 14 of the HF patients. Demodicidosis was not detected in the control group. Conclusions: This study showed that Demodex positivity is more common in HF patients hospitalized for HF exacerbation. Demodicidosis should be considered in hospitalized HF patients.

Is the presence of Demodex folliculorum increased with impaired glucose regulation in polycystic ovary syndrome?

Demodex parasites may cause skin and eyelash lesions by settling on the pilosebaceous unit. This parasite plays a role in the pathophysiology of acne in polycystic ovarian syndrome (PCOS). We aimed to examine the relationship between Demodex folliculorum and blood glucose control in patients with PCOS with skin and eyelash lesions. Forty-four patients with PCOS with skin lesions were enrolled in the study. At least two specimens were taken from the skin lesions using the standard method and at least six epilated eyelashes were taken from both eyes under a biomicroscope and evaluated using a light microscope. The demographic characteristics, body mass index (BMI) and clinical parameters of the patients were recorded. Demodex folliculorum was present at a rate of 59.1% in the skin lesions of the patients with PCOS, 40.9% in eyelash samples and 43.18% in both skin and lashes. Homeostasis model assessment of insulin resistance (HOMA-IR), glycosylated haemoglobin (HB A1c) concentrations, and BMIs were significantly higher in the patients who had D. folliculorum in skin samples than in those without (p = .010, p = .007 and p = .02). Impaired glucose regulation may explain the pathophysiology of the increased D. folliculorum presence in the skin lesions of patients with PCOS.Impact statementWhat is already known on this subject? Although several studies on Demodex folliculorum and PCOS have been conducted, we have not yet found a study that examines D. folliculorum parasites in the eyelashes and skin correlating with glucose regulation in PCOS. This study presents new information about the relationship between the presence of D. folliculorum and impaired glucose regulation in women with PCOS.What do the results of this study add? D. folliculorum is seen more commonly in skin lesions in patients with PCOS with impaired blood glucose regulation.What are the implications of these findings for clinical practice and/or further research? D. folliculorum is present in both skin and eyelash lesions in patients with PCOS. These lesions may be prevented by avoiding unregulated glucose levels and obesity. In future studies, the investigation of the resorption of D. folliculorum parasites in skin lesions with the continuation of normal glucose levels in patients with PCOS will reveal a more interesting linkage.

Erythematotelangiectatic rosacea may be associated with a subclinical stage of demodicosis: a case-control study

BACKGROUND

Facial densities of Demodex mites have been observed to be greater in patients with demodicosis and papulopustular rosacea than in healthy control patients. In patients with erythematotelangiectatic rosacea (ETR), this density has been observed to be similar to or greater than that of healthy controls. Erythema and telangiectasia, characteristics of ETR, are often observed among patients with pityriasis folliculorum, a discreet demodicosis, suggesting a possible link between these conditions.

OBJECTIVES

To compare the facial Demodex densities of patients with clinical ETR and patients with healthy skin, demodicosis, rosacea with papulopustules, and other facial dermatoses.

METHODS

In this retrospective study, we recorded Demodex densities measured using two consecutive standardized skin surface biopsies (SSSB1 and SSSB2) in 23 patients with ETR, 20 healthy control patients, 590 patients with demodicosis, 254 with rosacea with papulopustules and 180 with other facial dermatoses.

RESULTS

Patients with ETR had higher Demodex densities (D cm^-2 ) than did the healthy controls (mean ± SEM; SSSB1: 15·7 ± 6·3 vs. 1·8 ± 1·1 D cm^-2 , P = 0·042; SSSB2: 38·0 ± 13·7 vs. 5·1 ± 2·1 D cm^-2 , P = 0·026) and patients with other dermatoses (SSSB1: 0·4 ± 0·1 D cm^-2 , P = 0·004; SSSB2: 1·3 ± 0·3 D cm^-2 , P = 0·004), but lower densities than patients with demodicosis (SSSB1: 82·7 ± 4·2 D cm^-2 , P = 0·008; SSSB2: 172·2 ± 7·7 D cm^-2 , P = 0·001) or rosacea with papulopustules (SSSB1: 86·6 ± 7·3 D cm^-2 , P = 0·027; SSSB2: 197·0 ± 12·1 D cm^-2 , P = 0·002).

CONCLUSIONS

ETR may be associated with nonvisible Demodex proliferation, possibly corresponding to a subclinical stage of demodicosis. Dermatologists should be aware of this potential association and look for subclinical demodicosis in patients with ETR, so that topical acaricidal treatment can be offered if Demodex density is high.

Demodex mites modulate sebocyte immune reaction: possible role in the pathogenesis of rosacea

BACKGROUND

Rosacea is a common facial skin disorder mainly affecting middle-aged adults. Its aetiology is unknown and pathogenesis uncertain. Activation of the host innate immune response has been identified as an important factor. The Demodex mite population in the skin of rosacea patients is significantly higher than in patients with normal skin, suggesting that they may be of aetiological importance in this disorder.

OBJECTIVES

To determine the potential of Demodex mites to interact with the host immune system.

METHODS

Live Demodex mites were extracted from normal facial skin of control subjects and used in cell stimulation experiments with the immortalized SZ95 sebocyte line. Time- and mite-dose-dependent experiments were performed. Direct effects of Demodex and effects of the medium in which Demodex had been cultured were evaluated on the Toll-like receptor (TLR) signalling pathway on both a gene and protein expression level.

RESULTS

Mites modulated TLR signalling events on both mRNA and protein levels in SZ95 sebocytes. An initial trend towards downmodulation of genes in this pathway was observed. A subsequent switch to positive gene upregulation was recorded after 48 h of coculture. Demodex secreted bioactive molecules that affected TLR2 receptor expression by sebocytes. High numbers of Demodex induced proinflammatory cytokine secretion, whereas lower numbers did not.

CONCLUSIONS

Demodex mites have the capacity to modulate the TLR signalling pathway of an immortalized human sebocyte line. Mites have the capacity to secrete bioactive molecules that affect the immune reactivity of sebocytes. Increasing mite numbers influenced interleukin-8 secretion by these cells.

A Clinical Scoring System for Diagnosis of Ocular Demodicosis

Background

Demodex may cause chronic and refractory blepharitis with associated ocular surface problems, and its diagnosis and treatment can be quite challenging. In this study, our aim was to assess the efficacy of tea tree oil in Demodex treatment on caucasian patients in an industrialized region of Turkey, and to develop a systematic scoring system for extremely accurate diagnosis in the absence of advanced facilities.

Material/Methods

Charts of 412 patients with blepharitis were reviewed. A group of 39 out of 412 cases were identified as chronic and treatment-refractory, and therefore were enrolled in this study. Eyelashes from each of the lower and upper eyelids of both eyes were evaluated at ×40 and ×100 magnification using light microscopy. Treatment was started with 4% tea tree oil eyelid gel and 10% eyelash shampoo. Symptoms and findings were scored according to the most common complaints.

Results

The mean age of the patients was 54.1±15.4 years. Seventeen (43.5%) patients were male and 22 (56.5%) patients were female. In 30 out of the 39 patients (76.9%) D. folliculorum was detected. Symptoms disappeared in 25 patients. The mean score of patients who were Demodex-negative was 2.7±1.0, and the mean score of patients who were Demodex-positive was 3.8±1.6 (p=0.047). Ninety-four percent of those with a score of 4 and over were found to be Demodex-positive (p=0.025).

Conclusions

Treatment with tea tree oil can be successful. If there is no facility to identify Demodex under light microscopy, we recommend starting treatment for patients who have scores of 4 and over using the scoring chart developed in this study.

Demodex Folliculitis of the Scalp: Clinicopathological Study of an Uncommon Entity

Demodex is a saprophytic mite in humans commonly present in the pilosebaceous units, which has been implicated as a pathogen in several skin conditions. The clinical presentation and histopathology of Demodex folliculitis of the scalp have been described in only a few case reports. This study was performed to further elucidate the clinicopathological features of this entity. We have studied 333 consecutively submitted scalp biopsies performed for hair loss and alopecia. All specimens were completely step-sectioned. Biopsies with Demodex mites were further studied histopathologically, and the patients' clinical files were reviewed. There were 17 biopsies (5.1%) with Demodex in at least 1 pilosebaceous unit. Based on the clinical presentation, histopathology, and response to therapy, Demodex was considered to be nonpathogenic in 13 cases. The remaining 4 cases were characterized by hair loss, scalp erythema, scales, and pustules. There were 2 or more pilosebaceous units with Demodex along mononuclear and/or neutrophilic infiltrates around and in the involved follicles and occasionally granulomas. All 4 cases responded completely to metronidazole therapy. In conclusion, Demodex is infrequently found in scalp biopsies for hair loss and alopecia, and, in most cases, it does not seem to be pathogenic. Occasionally, however, it is associated with folliculitis characterized by hair loss, erythema, scales, and pustules clinically; neutrophilic and/or mononuclear-cell folliculitis with occasional granulomas histopathologically; and a prompt response to anti-Demodex therapy.

Neutrophilic sebaceous adenitis with intralobular Demodex mites: a case report and review of the literature

A 61-year-old white man presented with a 1-week history of an asymptomatic erythematous, annular plaque with minimal scale limited to the nasal bridge. Histological examination showed a mixed infiltrate of lymphocytes and neutrophils within sebaceous glands. The clinical and histopathological presentation was consistent with a diagnosis of neutrophilic sebaceous adenitis. Several Demodex brevis mites were present deep within the affected sebaceous lobules. Demodex brevis mites are uncommon inhabitants of sebaceous glands of the nose, presenting more commonly on other body sites. The cause of neutrophilic sebaceous adenitis is unknown, but the presence of D. brevis in affected sebaceous glands in this case suggests a possible association.

Prevalence of Demodex folliculorum and Demodex brevis in childhood malnutrition and malignancy

BACKGROUND

Hair follicle mites, Demodex folliculorum and Demodex brevis, are known to accompany immune-deficiency states, however no study so far has investigated their presence in malnutrition. In this study we aimed to determine the prevalence of those mites in childhood malnutrition, malignancy and risk factors.

METHODS

One hundred children with malnutrition, 31 children with malignancy and 63 children without any chronic disease and infection were included in this study. History, physical examination, anthropometric measurements and routine laboratory findings were recorded. Demodex spp. were investigated by standard superficial skin biopsies.

RESULTS

Demodex was found in 25 patients (25%), 10 patients (32.3%), and one patient (1.6%) among malnutrition, malignancy, and control groups, respectively (P = 0.001). By using multilogistic regression binary method, it was found that malnutrition, malignancy and low socioeconomic level increased the risk 17.37 times (P = 0.006), 27.29 times (P = 0.002), and 2.3 times (P = 0.037), respectively. Of 22 children who were evaluated after 6 months, 13 (59.1%) were negative for Demodex. In 11 (84.6%) of those 13, nutritional status was improved.

CONCLUSION

Demodex was detected in approximately in one-quarter and one-third of children with malnutrition and malignancy, respectively. Eliminating the cause of immunosuppression, such as poor nutritional status, seems also to be an effective method for eliminating Demodex.

A clinico-pathological approach to the classification of human demodicosis. Ein klinisch-pathologischer Ansatz zur Klassifikation der humanen Demodikose

BACKGROUND

Demodicosis is a parasitic skin disease caused by the follicle mites Demodex folliculorum and Demodex brevis. Although there are several clinical variants of this disease, a clear classification is missing.

OBJECTIVE

To characterize the clinical features and course of the different forms of demodicosis.

PATIENTS

Prospective study of 87 patients with clinical symptoms of demodicosis and positive acarological findings. Each patient was examined an average of six times during the treatment period.

RESULTS

We suggest that demodicosis be divided into both primary and secondary types. The usual etiological agent of primary demodicosis is D. folliculorum, which causes an erythemato-squamous eruption in the facial T-zone. The rash starts on unaltered skin and covers 8 - 15 % of the face. Pruritus accompanies the onset of the rash, while erythema is first apparent after papulo-pustules are seen and disappears after treatment. Half the patients show seasonal exacerbations. Secondary demodicosis is usually caused by D. brevis and characterized by a symmetrical malar papulo-pustular eruption. It develops on diseased skin and covers 30 - 40 % of the face. Pruritus starts after the lesion exacerbation, but erythema precedes the papulo-pustular phase and persists after treatment. Most patients flare during the summer. The facial distribution, seasonality and pathogenesis, as well as the species of mite involved, must be taken into consideration in separating the various forms of demodicosis.

Infestivity of Demodex canis to Hamster Skin Engrafted onto SCID Mice

We demonstrated that Demodex canis was transferred to skin xenografts of a dog and a hamster onto severe combined immunodeficiency mice. After the transfer of mites, the number of eggs, larvae, nymphs and adult mites per gram of canine and hamster xenografts increased, whereas no live mites were detected on murine allograft. These results indicate that D. canis proliferates in hair follicles of dog and hamster skins but not in murine allograft. Therefore, D. canis may have host preference but not strict host-specificity.

Immune response in demodicosis

BACKGROUND

Demodex folliculorum and Demodex brevis are obligatory parasites in the hair follicles and in the pilosebaceous glands. Although most people are infested with these mites, only a small number develop the clinical symptoms of demodicosis. The objective of this study was to determine the distinguishing features of the immune response to the infestation of the skin by Demodex mites.

METHODS

Twenty-nine patients with human demodicosis and 13 age- and sex-matched healthy subjects participated in the study. The presence of mites was determined by microscopic inspection of secretion from sebum glands. The immune response was evaluated in the peripheral blood by identifying membrane markers of different immune cells using monoclonal antibodies, while the concentration of immunoglobulin (Ig)A, IgM and IgG was calculated by simple radial immunodiffusion using anti-IgA, anti-IgM and anti-IgG. The level of circulating immune complexes and total haemolytic complement, as well as the preparatory and digestive function of neutrophils, and the functional activity of leucocytes were also studied.

RESULTS

The absolute number of CD95+ was higher in patients with demodicosis. The absolute number of CD3+, CD4+, CD8+ and CD16+ cells, the ratio CD3+/CD20+ and the functional activity of leucocytes were significantly lower in individuals infested with Demodex mites. No significant differences were found in the percentage and absolute number of CD20+ cells, the ratio of CD4+/CD8+ T-cell subpopulations, circulating immune complexes, level of serum complement activity (CH(50)), activity and index of phagocytosis and the levels of IgA, IgM and IgG antibodies between individuals infested with Demodex mites and the control group.

CONCLUSION

The readiness of lymphocytes to undergo apoptosis increases in parallel to the increasing density of the mites. This could be the result of local immunosuppression caused by the mites, which allows them to survive in the host skin.

Increased density of Demodex folliculorum and evidence of delayed hypersensitivity reaction in subjects with papulopustular rosacea

BACKGROUND

Rosacea is a common chronic dermatosis that evolves in stages. The mite Demodex folliculorum has been implicated in its obscure aetiopathogenesis.

AIM

To evaluate the importance of D. folliculorum in the aetiology and course of rosacea.

METHODS

We studied 92 consecutive cases of papulopustular rosacea and 92 age- and sex-matched controls. Prevalence and density of D. folliculorum were estimated by microscopic examination of the expressed follicular content. Histological examination and immunohistochemical study of the inflammatory infiltrate were performed in 10 subjects (five with positive D. folliculorum finding and five with negative finding).

RESULTS

D. folliculorum was detected in 83 (90.2%) of the 92 rosacea subjects but only 11(11.9%) of the controls. The mean mite density was 2.03 mites/visual field in the rosacea group (range 0-5, SD = 1.2) and 0.16 mites/visual field (range 0-2, SD = 0.52) in the control group. The difference was statistically significant (P < 0.0001) for both mite prevalence and density. Hair follicle infestation was associated with intense perifollicular infiltrate of predominantly (90-95%) CD4 helper/inducer T cells. We observed an increased number of macrophages and Langerhans cells only in those subjects with a positive D. folliculorum finding.

CONCLUSIONS

Although Demodex mites do not seem to be the cause of rosacea, they may represent an important cofactor, especially in papulopustular rosacea. Immunohistochemical findings suggest that a delayed hypersensitivity reaction, possibly triggered by antigens of follicular origin, probably related to D. folliculorum, may occur, stimulating progression of the affection to the papulopustular stage.

Demodex folliculorum in pregnancy

BACKGROUND

Demodex folliculorum (DF), which is a resident in human pilosebaceous follicles, has been implicated in rosacea, blepharitis, pityriasis folliculorum, pustular folliculitis, and skin lesions of immunosuppressed patients on chemotherapy or with acquired immunodeficiency syndrome (AIDS).

OBJECTIVE

We aimed to determine the influence of pregnancy on the carriage of DF.

METHODS

Mite density in 40 pregnant women was compared with that of age- and sex-matched controls. Two standardized skin surface biopsies were taken from each subject. Results In pregnant women, DF was found at 0.55/cm2, compared with a mean value of 1.2/ cm2 in nonpregnant controls. The difference between the two groups was not statistically significant (Mann-Whitney test, P = 0.22).

CONCLUSIONS

Our findings indicate that pregnancy may not have a direct effect on mite density.

[The prevalence of Demodex folliculorum and Demodex brevis in a population sample from Botucatu, São Paulo, Brazil]

A survey was conducted to determine the prevalence of D. folliculorum and D. brevis for the first time in Brazil. In this study, association between the presence of mites and host factors (age, sex and race) were analysed. Samples were obtained from 100 individuals submitted to a facial cleaning in an aesthetic clinic in Botucatu city. All the samples were mounted in Berlese's medium and examined by dark-field phase microscopy. From 100 studied individuals, 72 were positive, among the positive cases, 51% showed D. folliculorum, 2% showed D. brevis and 19% both species. The parasite distribution in relation to sex was not taken in account because the sex ratio favoured females (90%). According to age, prevalence was high in all age groups. The factors influencing this distribution could be due. 1. the examination of extensive skin areas, 2. the group examined composed of individuals in treatment in an anaesthetic clinic could be more infested than a normal population, 3. the fact that in tropics, the prevalence is often high in all ages.

Density of Demodex folliculorum in rosacea: a case-control study using standardized skin-surface biopsy

A standardized skin-surface biopsy (1 cm2) of the check was performed in 49 patients with rosacea [13 with erythemato-telangiectatic rosacea (ETR), three with squamous rosacea (SR), 33 with papulopustular rosacea (PPR)], and 45 controls. A mean density of 0.7 Demodex folliculorum/cm2 was found in controls, 98% of whom had less than five Demodex/cm2. When all clinical types of rosacea were considered collectively, the density of Demodex was significantly higher in patients with rosacea than in controls (mean = 10.8/cm2; P < 0.001). When the various clinical types of rosacea were considered separately, Demodex density was statistically significantly higher than in controls only in the PPR patients (mean = 12.8/cm2; P < 0.001). The same type of comparison was also made for three other groups of subjects--patients with isolated inflammatory papules (n = 4), rhinophyma (n = 3), and HIV infection (n = 21), respectively: in these groups, the Demodex density did not differ significantly from controls. The present study demonstrates a high density of D. folliculorum in PPR, and supports its pathogenic role in the papulopustular phase of rosacea. The study suggests that standardized surface biopsy could be a useful diagnostic tool for PPR, with a 98% specificity when Demodex density is higher than 5/cm2.

The Demodex mite population in rosacea

BACKGROUND

The cause of rosacea is unknown; among other factors a causative role has been postulated for the hair follicle mites Demodex folliculorum and Demodex brevis.

OBJECTIVE

Our purpose was to compare the population density of Demodex mites in facial skin of defined categories of patients with rosacea with control subjects. We also assessed the impact of tetracycline therapy on the mite population.

METHODS

The population density and distribution of Demodex mites were studied in the facial skin of 42 patients with rosacea and 42 age- and sex-matched control subjects. Mites were counted in measured skin surface biopsy specimens obtained from six standard facial sites with cyanoacrylate glue.

RESULTS

The mean mite count was 49.8 (range 2 to 158) in patients with rosacea and 10.8 (range up to 97) in control subjects (p < 0.001); the highest density of mites was found on the cheeks. A statistically significant increase in mites was found in all subgroups of rosacea, being most marked in those with steroid-induced rosacea. Mite counts in patients with rosacea before and after a 1-month course of oral tetracycline showed no significant difference.

CONCLUSION

Increased mites may play a part in the pathogenesis of rosacea by provoking inflammatory or allergic reactions, by mechanical blockage of follicles, or by acting as vectors for microorganisms.

Mites and related disease

Parasitic mites cause a variety of dermatoses in domestic animals. The clinical signs, diagnosis, and treatment of canine and feline demodicosis, canine scabies, notoedric mange, cheyletiellosis, otodectic mange, and other mite infestations are discussed.

Demodicosis and symbiophobia: status, terminology, and treatments

All patients are undoubtedly parasitized by hair follicle mites (D. brevis and/or D. folliculorum). Recovery of these may trigger or exacerbate phobias, so they should not be demonstrated on primary presentation. As adjunct treatment for all patients, one can recommend avoidance of long-term topical sterate or corticosteroid preparations, followed by use of daily lavage with soap and water. This is doubly important in sensitive or phobic patients, because ubiquitous demodecids may increase from 'normal' (greater than 5 per pilosebaceous complex) demodiciasis to marked (less than 10 mites) demodicosis. Evidence of phobia should, provisionally, be labelled with the nonperjorative term symbiophobia (herein coined for "fear of association with organisms"), and the causative organisms, if present, treated. Nonremission of phobias, despite counselling and treatment, should be referred to a sensitive, competent, medically trained psychiatrist.

Demodex folliculorum and Demodex brevis in cutaneous biopsies

The hair follicle mites Demodex folliculorum and Demodex brevis are ubiquitous obligatory ectoparasites of man. We studied these mites in a consecutive series of skin biopsies submitted to a dermatopathology laboratory; 10% of all biopsies and 12% of all follicles contained demodectic mites. The prevalence of both species increased with age, but D. brevis had a lower prevalence. The face was most heavily infested by both species, but D. brevis had a wider distribution on the body. Males were more heavily infested than females with both species, the difference being strongest for D. brevis. Other ecologic characteristics noted include the type of follicles infested, follicular dilation, perifollicular inflammation, and the presence of a dense homogeneous eosinophilic material surrounding the mites. These data confirm ecologic and epidemiologic differences between the two species and emphasize that they should be distinguished in future studies of the roles these mites may play in a variety of disease states.

Histopathology of meibomian gland dysfunction

We conducted a histopathologic study of he meibomian glands of seven patients (all men, ranging in age from 58 to 83 years) who had severe or moderately severe meibomian dysfunction and who were undergoing ectropion or entropion repair. Abnormal features included signs of obstruction and dilatation of ducts, enlargement of acini with cystic degeneration and squamous metaplasia, foreign-body reaction and granuloma formation, a mild increase in inflammatory cells, and abnormal keratinization. Demodex organisms were found in both acini and ducts of one patient. These findings were similar to those reported in other entities involving meibomian duct obstruction, probably related to abnormalities of keratinization, plays an important role in the pathogenesis of meibomian gland dysfunction.

Demodicosis of ophthalmic concern

Hair-follicle mites are the only metazoan organism commonly found in the pilosebaceous components of the eyelid of man. Our study showed that Demodex folliculorum in all stages is found in the small hair follicles and the eyelash hair follicles. This species, in adult and immature forms, consumes epithelial cells, produces follicular distension and hyperplasia, and increases keratinization leading, in eyelashes, to cuffing consisting of keratin and lipid moieties. Demodex brevis (in all stages) is present in the eyelash sebaceous glands, small hair sebaceous glands, and in the lobules of the meibomian glands. Adults and immature forms consume the gland cells in all of these loci and, when infestations are heavy, can affect the formation of the superficial lipid layer of the tear film coacervate. Comparative studies of demodicids from man and other mammals suggest that keratinization, hyperplasia, distension, and melanocyte aggregation may be even more extensive if large populations of D. folliculorum build up in the follicles of the eyelid. Large populations of D. brevis may destroy the glandular cells, produce granuloma in the eyelid, and plug the ducts of the meibomian or sebaceous glands. Further studies may incriminate either or both species, in conjunction with microorganisms, as transfer agents or synergists, or both, in producing ocular disease in man. Prevention and control of these mites must await experimental studies with infested laboratory animals (such as the squirrel monkey, Saimiri sciureus). These mites are probably most vulnerable during transfer stages, when they leave their glandular or follicular habitats.