Propionibacterium acnes and the Pathogenesis of Progressive Macular Hypomelanosis

Skin of color in dermatopathology: does color matter?

Skin of color (SoC) remains an understudied and under taught area of dermatology despite its rising importance. Race and ethnicity play a particularly important role in dermatology as skin pigmentation can affect the manifestation and presentation of many common dermatoses. With this review, we seek to review pertinent differences in SoC histology, as well as highlight the histopathology of conditions more common in SoC and address inherent bias that may affect accurate dermatopathology sign out.

Adolescent extra-truncal progressive macular hypomelanosis

Two adolescent females presented to outpatient clinic with isolated, non-scaly, asymptomatic hypopigmented macules and patches on the arm(s). Both cases had Wood's lamp exams notable for extralesional punctiform coral-red perifollicular fluorescence on the back and faint intralesional enhancement. In one case, biopsy was performed and deemed consistent with progressive macular hypomelanosis. The patient had complete response to antimicrobial therapy and sun exposure.

Post-Inflammatory Hypopigmentation: Review of the Etiology, Clinical Manifestations, and Treatment Options

Post-inflammatory hypopigmentation is a common acquired pigmentary disorder that is more prominent in skin of color, leading to great cosmetic and psychosocial implications. Often, a diagnosis with a pigmentary disorder can negatively impact an individual's health-related quality of life and may result in stigma. Although most cases of post-inflammatory hypopigmentation resolve spontaneously over time, a systematic diagnostic approach can help with identifying the underlying etiology and informing treatment strategies. It can be due to cutaneous inflammation, sequelae of inflammatory or infectious dermatoses, or dermatologic procedures. Therefore, a thorough understanding of the epidemiology, patient history, physical exam findings, and clinical features of post-inflammatory hypopigmentation phenomenon can explain the primary cause to providers and allow for patient education. It is also important to understand the various therapeutic approaches available and the efficacy of these options, which will inform providers to choose the appropriate therapy for patients. Although algorithms exist for classifying acquired disorders of hypopigmentation, there are no established algorithms for the diagnosis and treatment of post-inflammatory hypopigmentation, which warrants further exploration and discourse.

Is Cutibacterium (previously Propionibacterium) acnes a potential pathogenic factor in the aetiology of the skin disease progressive macular hypomelanosis?

Progressive macular hypomelanosis (PMH) is a skin condition that normally causes symmetrically distributed hypopigmented macules on the front and back of the trunk, but rarely the face. To date, the pathophysiology of the condition is not well understood, but a role for the anaerobic skin bacterium Cutibacterium (previously Propionibacterium) acnes in the development of the disease has been proposed due to its sole presence within lesional, but not normal peri-lesional, skin. The success of antimicrobials in the treatment of PMH also provides circumstantial evidence that this association may be causal, although this is still to be proven. More recent culture and metagenomic typing studies indicate that strains of C. acnes subsp. elongatum (type III) may be important in the aetiology of the condition, which would help to explain why PMH does not normally affect the face since such strains are rarely present there, and why no association between this condition and acne vulgaris is found; acne appears to primarily involve type IA₁ strains from C. acnes subsp. acnes (type I). In this review, we summarize current knowledge on the relationship between C. acnes and PMH, and re-examine previous challenges to the view that the bacterium plays a role in the condition against the backdrop of newly emerged data.

Low dose of isotretinoin: A comprehensive review

Isotretinoin is a first-generation retinoid initially approved for the treatment of severe cases of acne vulgaris (nodulocystic acne). Because of its broad anti-inflammatory and immunomodulatory properties, it has been used beyond its initial approval in a myriad of other indications. Adverse effects of isotretinoin vary from xerosis to teratogenicity. Herein, we reviewed the literature, through date-unlimited PubMed search, from inception till December 2019, using the following search terms: "low-dose isotretinoin" and "dermatology," "isotretinoin and safety," "isotretinoin, off-label uses," "isotretinoin and male fertility," "isotretinoin, iPLEDGE system," aiming to deliver a therapeutic update relevant to clinical practice. All English-language articles were considered with no limitation based on the articles' type. Low-dose isotretinoin is not limited to old and novel dermatological conditions, but also showed promising results in the field of infertility and safety in the field of gastroenterology. We also highlight on the safety profile of the drug and experts' recommendations to enhance safety measures to decrease fetal risk while on isotretinoin.

Porphyrin Production and Regulation in Cutaneous Propionibacteria

Porphyrins are intermediate metabolites in the biosynthesis of vital molecules, including heme, cobalamin, and chlorophyll. Bacterial porphyrins are known to be proinflammatory, with high levels linked to inflammatory skin diseases. Propionibacterium species are dominant skin commensals and play essential roles in defending against pathogens and in triggering an inflammatory response. To better understand how the inflammatory potential of the skin microbiome may vary depending on its propionibacterial composition, we compared the production levels of porphyrins among Propionibacterium acnes, Propionibacterium granulosum, Propionibacterium avidum, and Propionibacterium humerusii strains. We found that porphyrin production varied among these species, with P. acnes type I strains producing significantly larger amounts of porphyrins than P. acnes type II and III strains and other Propionibacterium species. P. acnes strains that are highly associated with the common skin condition acne vulgaris responded to vitamin B₁₂ supplementation with significantly higher porphyrin production. In contrast, vitamin B₁₂ supplementation had no effect on the porphyrin production of health-associated P. acnes strains and other propionibacteria. We observed low-level porphyrin production in most Propionibacterium strains harboring the deoR repressor gene, with the exception of P. acnes strains belonging to type I clades IB-3 and IC. Our findings shed light on the proinflammatory potential of distinct phylogenetic lineages of P. acnes as well as other resident skin propionibacteria. We demonstrate that the overall species and strain composition is important in determining the metabolic output of the skin microbiome in health and disease.IMPORTANCE Porphyrins are a group of metabolites essential to the biosynthesis of heme, cobalamin, and chlorophyll in living organisms. Bacterial porphyrins can be proinflammatory, with high levels linked to human inflammatory diseases, including the common skin condition acne vulgaris. Propionibacteria are among the most abundant skin bacteria. Variations in propionibacteria composition on the skin may lead to different porphyrin levels and inflammatory potentials. This study characterized porphyrin production in all lineages of Propionibacterium acnes, the most dominant skin Propionibacterium, and other resident skin propionibacteria, including P. granulosum, P. avidum, and P. humerusii We revealed that P. acnes type I strains produced significantly more porphyrins than did type II and III strains and other Propionibacterium species. The findings from this study shed light on the proinflammatory potential of the skin microbiome and can be used to guide the development of effective acne treatments by modulating the skin microbiome and its metabolic activities.

Common Skin Disorders in Pediatric Skin of Color

Children with skin of color represent a large proportion of the pediatric population. There are numerous skin conditions that commonly occur in this population, including but not limited to acne, atopic dermatitis, pityriasis alba, tinea versicolor, progressive macular hypomelanosis, traction alopecia, and confluent and reticulated papillomatosis. This article highlights the clinical presentations of these conditions in skin of color and briefly addresses pathophysiology and treatment modalities.

Presentations, Signs of Activity, and Differential Diagnosis of Vitiligo

Vitiligo has a variety of presentations, including focal, acrofacial, segmental, and generalized forms. Thorough knowledge of these presentations is important to make the correct diagnosis. Signs of activity are important to recognize so that treatment is optimized. Clinical findings of confettilike depigmentation, trichrome and inflammatory vitiligo, and the Koebner phenomenon should alert the clinician that a patient's disease is likely to worsen. These patients may require systemic treatment to stabilize their disease. Many other skin disorders present with hypopigmentation or depigmentation and must be distinguished to determine the right diagnosis, advise the patient on prognosis, and prescribe the correct treatment.

Propionibacterium Acnes Phylogenetic Type III is Associated with Progressive Macular Hypomelanosis

Progressive macular hypomelanosis (PMH) is a skin disorder that is characterized by hypopigmented macules and usually seen in young adults. The skin microbiota, in particular the bacterium Propionibacterium acnes, is suggested to play a role.

Here, we compared the P. acnes population of 24 PMH lesions from eight patients with corresponding nonlesional skin of the patients and matching control samples from eight healthy individuals using an unbiased, culture-independent next-generation sequencing approach. We also compared the P. acnes population before and after treatment with a combination of lymecycline and benzoylperoxide.

We found an association of one subtype of P. acnes, type III, with PMH. This type was predominant in all PMH lesions (73.9% of reads in average) but only detected as a minor proportion in matching control samples of healthy individuals (14.2% of reads in average). Strikingly, successful PMH treatment is able to alter the composition of the P. acnes population by substantially diminishing the proportion of P. acnes type III.

Our study suggests that P. acnes type III may play a role in the formation of PMH. Furthermore, it sheds light on substantial differences in the P. acnes phylotype distribution between the upper and lower back and abdomen in healthy individuals.

Strains of the Propionibacterium acnes type III lineage are associated with the skin condition progressive macular hypomelanosis

Progressive macular hypomelanosis (PMH) is a common skin disorder that causes hypopigmentation in a variety of skin types. Although the underlying aetiology of this condition is unclear, there is circumstantial evidence that links the skin bacterium Propionibacterium acnes to the condition. We now describe the first detailed population genetic analysis of P. acnes isolates recovered from paired lesional and non-lesional skin of PMH patients. Our results demonstrate a strong statistical association between strains from the type III phylogenetic lineage and PMH lesions (P = 0.0019), but not those representing other phylogroups, including those associated with acne (type IA₁). We also demonstrate, based on in silico 16S rDNA analysis, that PMH isolates previously recovered from patients in Europe are also consistent with the type III lineage. Using comparative genome analysis, we identified multiple genomic regions that are specific for, or absent from, type III strains compared to other phylogroups. In the former case, these include open reading frames with putative functions in metabolism, transport and transcriptional regulation, as well as predicted proteins of unknown function. Further study of these genomic elements, along with transcriptional and functional analyses, may help to explain why type III strains are associated with PMH.

Taxonomy, Physiology, and Natural Products of Actinobacteria

Actinobacteria are Gram-positive bacteria with high G+C DNA content that constitute one of the largest bacterial phyla, and they are ubiquitously distributed in both aquatic and terrestrial ecosystems. Many Actinobacteria have a mycelial lifestyle and undergo complex morphological differentiation. They also have an extensive secondary metabolism and produce about two-thirds of all naturally derived antibiotics in current clinical use, as well as many anticancer, anthelmintic, and antifungal compounds. Consequently, these bacteria are of major importance for biotechnology, medicine, and agriculture. Actinobacteria play diverse roles in their associations with various higher organisms, since their members have adopted different lifestyles, and the phylum includes pathogens (notably, species of Corynebacterium, Mycobacterium, Nocardia, Propionibacterium, and Tropheryma), soil inhabitants (e.g., Micromonospora and Streptomyces species), plant commensals (e.g., Frankia spp.), and gastrointestinal commensals (Bifidobacterium spp.). Actinobacteria also play an important role as symbionts and as pathogens in plant-associated microbial communities. This review presents an update on the biology of this important bacterial phylum.

100 years of Wood's lamp revised

The Wood's lamp is a diagnostic tool in dermatology. Unfortunately, this useful tool is often overlooked in the busy and hectic outdoor dermatology clinic. To emphasize its value in modern dermatology, we present an updated review of the principles and applications and shed new light on its proper place in our practice.

Progressive macular hypomelanosis

Progressive macular hypomelanosis (PMH) is a condition of unknown etiology characterized by asymptomatic, hypopigmented macules located predominantly on the trunk. We recorded 12 adolescents with PMH over a 6-month period. Ten were female, and the mean age was 16.6 years. The average time from the patients first noticing pigment change to diagnosis was 15 months. PMH is probably an underdiagnosed condition.

Investigation of Propionibacterium acnes in progressive macular hypomelanosis using real-time PCR and culture

BACKGROUND

Progressive macular hypomelanosis (PMH) is a dermatosis of unknown etiology. It has been concluded that it involves the presence of Propionibacterium acnes, a saprophyte of the pilosebaceous follicles. In our study, we investigated the presence of P. acnes in lesional and non-lesional skin of patients with PMH through quantitative real-time polymerase chain reaction (PCR) and bacterial culture from a skin fragment.

MATERIALS AND METHODS

An observational, exploratory study, with laboratory comparison of lesional (study group) and non-lesional skin (comparison group), in patients with PMH, was carried out with 36 patients, seen in the dermatology outpatient setting at the Oswaldo Cruz University Hospital (OCUH), Recife, Pernambuco, Brazil, between March and May 2008. All patients were submitted to a Wood's lamp examination, mycological research, and biopsies of lesional and non-lesional skin from the back. Skin fragments were submitted to a histopathology test, bacterial culture, and a quantitative real-time PCR test. The program Statistical Package for Social Sciences, version 12.0, was employed for relationship analysis with the Wilcoxon and McNemar tests.

RESULTS

There was a significant predominance of P. acnes on lesional skin, in comparison to non-lesional skin (P<0.001), as demonstrated by culture and quantitative real-time PCR.

CONCLUSION

Although P. acnes is a saprophyte, the hypothesis may be raised that this microorganism participates in the development of PMH.

The use of lymecycline and benzoyl peroxide for the treatment of progressive macular hypomelanosis: a prospective study

Progressive macular hypomelanosis is a dermatosis of uncertain etiology. The participation of Propionibacterium acnes has been suggested in view of the response achieved following therapy with drugs that are active against this bacterium. This report describes a series of thirteen patients with progressive macular hypomelanosis who were treated with an association of lymecycline and benzoyl peroxide over a three-month period. Response to treatment was excellent and the positive results were maintained during the entire follow up period.

Efficacy of topical combination of benzoyl peroxide 5% and clindamycin 1% for the treatment of progressive macular hypomelanosis: a randomized, doubleblind, placebo-controlled trial

BACKGROUND

Progressive macular hypomelanosis is a dermatosis without definite etiology. There is no consensus or first-line therapy in the treatment of progressive macular hypomelanosis, and the treatment options used are very little effective.

OBJECTIVE

To evaluate the therapeutic efficacy of the topical combination of benzoyl peroxide 5% and clindamycin 1% associated with sun exposure for the treatment of progressive macular hypomelanosis.

MATERIALS AND METHODS

This is a randomized, double-blind, placebo-controlled study in which patients were divided into two groups. Group A used the topical combination of benzoyl peroxide 5% and clindamycin 1% and Group B used gel cream as a placebo. Patients were advised to expose themselves to the sun on a daily basis and were systematically evaluated and photographed. The collected data were entered and analyzed using Epi Info. A p value < 0.05 was considered statistically significant.

RESULTS

Out of the 23 patients included in the study, 13 were in group A and 10 in group B. Eleven patients (85%) in group A had significant clinical improvement and only two patients (20%) in group B showed an equivalent clinical improvement (p = 0.003). Side effects were more frequent in group A (p = 0.003).

CONCLUSION

The topical combination of benzoyl peroxide 5% and clindamycin 1% is effective in the treatment of progressive macular hypomelanosis.

Narrowband UVB treatment of progressive macular hypomelanosis

BACKGROUND

Little information is available on effective treatments for progressive macular hypomelanosis (PMH). To our knowledge, only one case of narrowband ultraviolet B (NB-UVB) therapy as an efficient treatment for patients with PMH has been reported in the recent literature.

OBJECTIVE

We aimed to investigate the clinical features of PMH in Koreans and to determine the therapeutic efficacy of NB-UVB therapy in the management of PMH.

METHODS

We performed an uncontrolled prospective study designed to evaluate the usefulness of NB-UVB therapy in PMH. A total of 23 patients with PMH were enrolled in the study. Of these, 17 patients underwent treatment with NB-UVB therapy once or twice weekly and were eligible for analysis. The remaining 6 patients were lost to follow-up before completion of the treatment. Repigmentation was evaluated by two dermatologists using photographic documentation.

RESULTS

In our trial, NB-UVB therapy was used successfully in 9 of 16 patients (56.2%), who showed more than 90% repigmentation. We found that 13 of 16 patients (81.3%) experienced at least 50% repigmentation. The repigmented sites showed an excellent color match. No signs of recurrence have been detected in 11 of these 16 patients (68.7%) up to the present time (13.2 ± 8.2 months of follow-up).

LIMITATIONS

Our study includes a small number of subjects examined, and it was an uncontrolled and non-double-blind study.

CONCLUSIONS

The findings of this study suggest that NB-UVB therapy is an effective and safe method for use in the treatment of PMH.

A quantitative analysis of Propionibacterium acnes in lesional and non-lesional skin of patients with progressive macular hypomelanosis by real-time polymerase chain reaction

Little is known about the etiology of progressive macular hypomelanosis, although it has been suggested that Propionibacterium acnes plays an important role. While microbiological culture is commonly employed to identify Propionibacterium acnes, new identification methods have been under investigation, amongst them polymerase chain reaction. To determine the cut-off point for the number of genome copies of Propionibacterium acnes in the lesional skin of patients with progressive macular hypomelanosis as a positive marker, employing quantitative real-time polymerase chain reaction and anaerobic culture, considered gold standard. An observational study with a comparison group, included 35 patients with dermatosis, attended at the Oswaldo Cruz University Hospital, Pernambuco, Brazil, between March and May 2008. Lesional skin was compared to non-lesional skin through positive testing with real-time polymerase chain reaction and culture. The Statistical Package for Social Sciences, version 12.0, was employed for the association analysis with the McNemar test, and the cut-off point with the ROC curve for maximum values. Propionibacterium acnes was most frequently encountered in lesional areas (p<0,025). The cut-off point of Propionibacterium acnes in lesional skin was 1,333 genome copies, with a sensitivity of 87,9% and a specificity of 100,0%. Since Propionibacterium acnes is a saprophyte, identifying the cut-off point may assist in determining its positivity in lesional skin in patients suffering with this dermatosis.

Comparison of the clinical efficacy of NBUVB and NBUVB with benzoyl peroxide/clindamycin in progressive macular hypomelanosis

BACKGROUND

Progressive macular hypomelanosis (PMH) is a skin disorder characterized by multiple hypopigmented patches symmetrically distributed on the trunk. Several treatment modalities have been attempted; however, a standard treatment modality has not been agreed to.

OBJECTIVES

The aim of this study was to compare the effectiveness of antimicrobial therapy combined with narrow band ultraviolet B (NBUVB) with NBUVB monotherapy.

METHODS

A randomized left-right comparison study was conducted in a total of 10 patients. Patients received NBUVB therapy with daily application of antimicrobial gel on one side of the trunk (comb-NBUVB) and without it (mono-NBUVB) for 8 weeks. The clinical efficacy was determined by objective measurements using a colour analyser and subjective assessment by evaluating pictures taken with a digital camera at baseline, at the time of treatment cessation and 6 months after treatment.

RESULTS

Significant repigmentation was observed in all 10 patients during the 8 weeks of treatment. The mean difference in L values between lesional and non-lesional skin was reduced in the comb-NBUVB area (from 4.52 ± 1.65 to 0.94 ± 0.65), and in the mono-NBUVB area, (from 4.34 ± 1.39 to 1.18 ± 0.94). There was no significant difference between treated sites at both of the evaluation points in time. At 6 months after treatment, 7 of 10 patients completed the clinical trial, and some degree of clinical improvement remained in four of seven patients; recurrence occurred in the other patients.

CONCLUSIONS

Although recurrence occurred in some patients, NBUVB treatment appears to be a safe and useful modality for the treatment of PMH.

Hipomelanose macular progressiva: estudo epidemiológico e resposta terapêutica à fototerapia

FUNDAMENTOS: A hipomelanose macular progressiva é uma dermatose comum em diferentes continentes. Sua causa é desconhecida e os tratamentos propostos são pouco eficazes. OBJETIVOS: Determinar aspectos epidemiológicos da hipomelanose macular progressiva em pacientes atendidos num setor de fototerapia, no período de 1997 a 2008, e avaliar a resposta terapêutica com PUVA ou UVBNB. MÉTODOS: Foram avaliados 84 pacientes com Hipomelanose Macular Progressiva. Após 16 sessões de fototerapia, a resposta terapêutica foi definida: I=inalterado, MD=melhora discreta(< 50% de repigmentação), MM=melhora moderada(50-79%), MI=melhora intensa(80-99%) e C=cura(100%). Após um tempo mínimo de três meses, pacientes com cura ou MI foram contatados por telefone para avaliar a manutenção do resultado terapêutico. RESULTADOS: Predominaram mulheres (79%) e a cor branca. A idade mínima de aparecimento da Hipomelanose Macular Progressiva foi de 13 anos e a máxima de 36 anos. Fototerapia com PUVA foi indicada em 27 pacientes e UVBNB em 57. Estatisticamente, não houve diferença significante entre o tratamento com PUVA e UVBNB (teste de Fisher P>0.05). A maioria (81%) dos pacientes obteve 50% ou mais de repigmentação e 65% tiveram cura ou MI. Entretanto, 72% apresentaram recorrência das lesões. CONCLUSÃO: A ausência de pacientes, com mais de 40 anos, sugere que a Hipomelanose Macular Progressiva seja uma doença autolimitada. Tanto PUVA como UVB NB são opções terapêuticas, porém não impedem a recidiva da doença.

Progressive macular hypomelanosis in korean patients: a clinicopathologic study

BACKGROUND

Progressive macular hypomelanosis is characterized by ill-defined, non-scaly, hypopigmented macules primarily on the trunk of the body. Although numerous cases of progressive macular hypomelanosis have been reported, there have been no clinicopathologic studies of progressive macular hypomelanosis in Korean patients.

OBJECTIVE

In this study we examined the clinical characteristics, histologic findings, and treatment methods for progressive macular hypomelanosis in a Korean population.

METHODS

Between 1996 and 2005, 20 patients presented to the Department of Dermatology at Busan Paik Hospital with acquired, non-scaly, confluent, hypopigmented macules on the trunk, and with no history of inflammation or infection. The medical records, clinical photographs, and pathologic findings for each patient were examined.

RESULTS

The patients included 5 men and 15 women. The mean age of onset was 21.05+/-3.47 years. The back was the most common site of involvement. All KOH examinations were negative. A Wood's lamp examination showed hypopigmented lesions compared with the adjacent normal skin. A microscopic examination showed a reduction in the number of melanin granules in the lesions compared with the adjacent normal skin, although S-100 immunohistochemical staining did not reveal significant differences in the number of melanocytes. Among the 20 patients, 7 received topical drug therapy, 6 were treated with narrow-band ultraviolet B phototherapy, 4 received oral minocycline, and 3 did not receive any treatment.

CONCLUSION

Most of the patients with progressive macular hypomelanosis had asymptomatic ill-defined, non-scaly, and symmetric hypopigmented macules, especially on the back and abdomen. Histologically, the number of melanocytes did not differ significantly between the hypopigmented macules and the normal perilesional skin. No effective treatment is known for progressive macular hypomelanosis; however, narrow-band ultraviolet B phototherapy may be a useful treatment modality.

Progressive macular hypomelanosis: a rarely diagnosed hypopigmentation in Caucasians

A 35-year-old woman who developed whitish macules on trunk and limbs at 12 years of age and observed a remarkable increase of the hypopigmentated lesions after her pregnancies at ages 29 and 32 years. Because of the highly characteristic clinical aspect and the light- and electron-microscopic histopathologic findings, we diagnosed progressive macular hypomelanosis (PMH). It is a nonscaly disorder with hypopigmented macules mainly on the trunk and is more often seen in young women. In contrast to some authors assuming the presence of Propionibacterium spp. as a matter of principle in PMH, we report a case with no evidence for Propionibacterium spp.

Ultrastructural findings in progressive macular hypomelanosis indicate decreased melanin production

BACKGROUND

The pathogenesis of progressive macular hypomelanosis (PMH) is unknown. Recently, Westerhof et al. (Arch Dermatol 2004; 140: 210-214) hypothesized that Propionibacterium acnes produces a depigmenting factor that interferes with melanogenesis in the skin, resulting in hypopigmented spots. The purpose of the study is to gain an insight into the pathogenesis of PMH.

MATERIALS AND METHODS

We took a biopsy of 2-mm diameter from normal and lesional skin in eight PMH patients. Using electron microscopy, we compared melanization of melanosomes, melanosome transfer and amount of epidermal melanin in normal and lesional skin.

RESULT

Compared to non-lesional skin, we observed a decrease of epidermal melanin and less melanized melanosomes in lesional skin of all patients. When comparing normal and lesional skin of patients with skin type V and VI, we observed a difference in melanosome size and maturation and a switch of transferred melanosomes from single stage IV transferred melanosomes to aggregated stage I, II and III transferred melanosomes, as seen in healthy skin of skin type I to IV.

CONCLUSION

Hypopigmentation in PMH seems to be the result of an altered melanogenesis based on a decrease in melanin formation and a change in the distribution of melanosomes. In lesional skin of PMH patients with skin type V and VI less melanized, aggregated melanosomes in stead of single, mature melanosomes are transferred from melanocytes to keratinocytes. This results in a decrease of epidermal melanin. Further investigations are needed to determine the precise role of Propionibacterium acnes in this alteration of melanogenesis.

Progressive macular hypomelanosis in a 16-year old

Progressive macular hypomelanosis of the trunk is a disease of unclear etiology that often goes unrecognized in the clinical setting. We present a Caucasian adolescent girl with hypopigmented macules coalescing into patches on her trunk, initially diagnosed as tinea versicolor. Upon further evaluation, the patient was found to have progressive macular hypomelanosis that demonstrated improvement with sunlight exposure and doxycycline. We report this patient to make physicians more aware of this entity and discuss the literature.

Origin, clinical presentation, and diagnosis of hypomelanotic skin disorders

Hypomelanotic skin disorders are cutaneous pigmentary disorders characterized by a reduced melanin content in the skin that results in a lightening of the skin. Establishing the correct diagnosis for hypomelanotic skin disorders requires a good history, a detailed physical examination, the use of special lighting techniques, such as Wood's light, and sometimes a biopsy of the abnormally pigmented skin and the normally pigmented skin. This article focuses on the origin, clinical presentation, and diagnosis of acquired hypomelanotic skin disorders. An algorithm for the diagnostic approach to these hypomelanoses is given.

Pigmentary Disorders in Latin America

Pigmentary disorders with hypopigmentation/depigmentation or hyperpigmentation may have special manifestations in Latin America. Most pigmentary disorders are commonly observed in all areas of Latin America, but a few are particularly seen in tropical and subtropical regions. In most pigmentary disorder ailments described, multiple factors involved in their pathogenesis are known, but etiology remains elusive. Some pigmentary disorders have peculiar clinical expressions and, in spite of being restricted to certain geographical areas, they may be observed in other world areas because of frequent traveling of affected patients. Therapy of most of these ailments is difficult or remains unknown.

Progressive macular hypomelanosis: an overview

Progressive macular hypomelanosis (PMH) is a common skin disorder that is often misdiagnosed. Various authors have written about similar skin disorders, referring to them by different names, but we believe that all these similar disorders are part of the same entity.PMH is characterized by ill-defined nummular, non-scaly hypopigmented spots on the trunk, often confluent in and around the midline, and rarely extending to the proximal extremities and neck/head region. There is no itch, pain, or preceding inflammation. PMH has a worldwide distribution; however, it is more often identified in Black people living in or originating from tropical countries. It is also more often seen in young females. The natural history of PMH is stable disease or perhaps slow progression over decades, with spontaneous disappearance after mid-life. Extensive pityriasis alba is probably identical with PMH and we suggest discontinuation of use of the former term on the grounds that extensive pityriasis alba is histologically and clinically different from classical pityriasis alba, which is basically an eczematous type of disorder.PMH is characterized histologically by diminished pigment in the epidermis and a normal-looking dermis. Electron microscopy shows a shift from large melanosomes in normal-looking skin to small aggregated, membrane-bound melanosomes in hypopigmented skin. PMH should be differentiated from other disorders with hypopigmentation on the trunk such as pityriasis versicolor. We propose that Propionibacterium acnes bacteria living in hair follicles are the cause of PMH as a result of production of a hypothetical depigmenting factor. This hypothesis is based on: (i) the presence of a red follicular fluorescence in the hypopigmented spots and the absence of this phenomenon in normal skin when examined under a Wood's light in a dark room; (ii) cultivation of P. acnes from the follicles in the hypopigmented spots but not from follicles in normal-looking skin; and (iii) improvement of the disorder after elimination of these micro-organisms with topical antimicrobial treatment in combination with UVA light.Currently, the treatment of choice of PMH is application of 1% clindamycin lotion during the daytime, 5% benzoyl peroxide gel at night-time, and UVA light irradiation three times a week for a period of 12 weeks. There is insufficient information available as yet to comment on the recurrence rate after therapy.

Benzoyl peroxide/clindamycin/UVA is more effective than fluticasone/UVA in progressive macular hypomelanosis: A randomized study

BACKGROUND

There is no effective treatment for progressive macular hypomelanosis. Recent findings indicate that Propionibacterium acnes may play a role in the pathogenesis.

OBJECTIVES

We sought to compare the effectiveness of antimicrobial therapy with anti-inflammatory therapy in patients with progressive macular hypomelanosis.

METHODS

A total of 45 patients were randomized to a within-patient left-right comparison study of benzoyl peroxide 5% hydrogel/clindamycin 1% lotion in combination with UVA irradiation versus fluticasone 0.05% cream in combination with UVA irradiation. Repigmentation was determined by photometric measurements of changes in skin color and by patient and dermatologist assessment using before and after photographs.

RESULTS

Benzoyl peroxide 5% hydrogel, clindamycin 1% lotion, and UVA led to better repigmentation than fluticasone 0.05% cream in combination with UVA irradiation in all measurements. (Photometric measurements P = .007, patient assessment P < .0001, and dermatologist assessment P < .0001.)

LIMITATIONS

There was difficult objective color measurement. Therefore, subjective assessment has important additional value. Right-left comparisons have certain inherent limitations.

CONCLUSION

Antimicrobial therapy in conjunction with light was more effective in repigmentation in patients with progressive macular hypomelanosis than a combination of anti-inflammatory therapy and light.

Progressive macular hypomelanosis in Singapore: a clinico-pathological study

INTRODUCTION

Progressive macular hypomelanosis (PMH), a condition of uncertain etiology, is characterized by asymptomatic hypopigmented macules predominantly located on the trunk. To date, there are no reports from South-East Asia concerning this condition. We sought to record the clinical features of PMH in Asian patients, identify etiologic factors, and study the structural and ultrastructural features of melanocytes in this disorder.

METHODS

Patients who presented to the National Skin Center with acquired, hypopigmented macules on the trunk, without a history of inflammation or infection, were recruited. Erythrocyte sedimentation rate (ESR), complete blood count, fasting blood glucose, liver function tests, skin scrapings for fungi, and skin biopsy specimens (from lesional and normal skin) were obtained. Biopsies were stained with hematoxylin and eosin (H&E), Fontana Masson, an immunohistochemical panel for identification of melanocyte differentiation antibodies (HMB 45, Melan A, and S100) and CD 68. Electron microscopy (EM) was also performed. The patients were evaluated every 3 months.

RESULTS

During a 9 month period, eight patients (all Chinese) presented with hypopigmented, ill-defined, confluent macules involving the lower aspect of the trunk. There were four men and four women, and the mean age was 25.9 years (range 19-45 years). Skin scrapings were negative for fungi and laboratory tests were normal. Microscopic evaluation of skin biopsy specimens showed reduced pigmentation of lesional as compared with normal appearing skin, but H&E-stained sections revealed only minimal histologic differences between lesional and normal skin. EM demonstrated a statistically significant (P = 0.047, Wilcoxon Signed Rank Test, Wilcoxon 95% CI 0.02-0.62) higher ratio of stage IV and late stage III (dark) melanosomes in normal vs. lesional skin.

CONCLUSIONS

PMH may occur among young adults in Singapore. Its etiology is uncertain. The melanin content of lesional skin appears to be less than that in normal sites. EM shows a higher ratio of immature melanosomes in lesional vs. normal skin.

Insights in the Pathogenic Potential of Propionibacterium acnes From Its Complete Genome

One of the long-lasting open questions in understanding acne is the role of the skin bacterium Propionibacterium acnes. Opinions within the scientific community diverge regarding the importance of this Gram-positive bacterium not only in acne but also in other P. acnes-associated diseases. The recently decoded genome gives us some clues with respect to its pathogenic potential and its strategies to survive in the harsh environment of human skin. This review focuses on the major findings of the genome sequence. Special attention has been drawn to the cell surface composition of P. acnes, its antigenic potential, and to enzymes that are potentially involved in degrading skin-derived substances.