Molluscum contagiosum (MC) is a very common viral infection. It produces dome shaped flesh colored papules measuring 2-5 mm in diameter. It is caused by the Molluscum contagiosum virus and is prevalent in sexually active adults, young children, and immunocompromised patients. The lesions may persist for weeks to months suggesting the virus provokes a minimal cell-mediated immunity.
Epidemiology Disease Associations Pathogenesis Laboratory/Radiologic/Other Diagnostic Testing Gross Appearance and Clinical Variants Histopathological Features and Variants Special Stains/
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EPIDEMIOLOGY CHARACTERIZATION AGE
J Am Acad Dermatol. 2006 Jan;54(1):47-54. Epub 2005 Nov 21. Abstract quote
Molluscum contagiosum (MC) is a viral disorder of the skin and mucous membranes characterized by discrete single or multiple, flesh-colored papules. Although MC as a clinical entity is well defined and commonly observed, few data regarding its epidemiology in the pediatric population exist.
Our purpose was to collect epidemiologic data on children with MC with regard to age, gender, ethnicity, degree of involvement, relation to pre-existing atopic dermatitis (AD), and immune status. A retrospective chart review was conducted. All subjects were seen at 3 tertiary pediatric dermatology referral centers with two of the sites based at a Children's Hospital. A total of 302 patient charts with the Current Procedural Terminology code diagnosis of MC seen over a 6- to 8-month period were reviewed. Approximately 80% of the patients were younger than 8 years old. The majority of patients (63%) had more than 15 lesions. All but one patient were otherwise healthy, as determined by history and clinical examination. Approximately 24% of the patients presented with a history of previous or active coexistent AD. However, children with AD were at risk for an increased number of lesions.
These data provide valuable updated information on the demographics and clinical presentation of MC in pediatric patients in the United States. Limitations include that this was a retrospective study with a population limited to tertiary pediatric dermatology referral centers.
Molluscum contagiosum virus: antibody responses in persons with clinical lesions and seroepidemiology in a representative Australian population.
Konya J, Thompson CH.
Department of Infectious Diseases, Faculty of Medicine, University of Sydney, Sydney, New South Wales 2006, Australia.
J Infect Dis 1999 Mar;179(3):701-4 Abstract quote
An ELISA for molluscum contagiosum virus (MCV) was used to determine the antibody status of 35 adults with clinical infections and known human immunodeficiency virus (HIV) serology and of 357 persons (ages, 1 week-69 years) considered representative of the Australian population. MCV antibody was identified in 77% of persons with molluscum lesions: in 17 of 24 HIV-1-negative persons and in 10 of 11 who were HIV-1-positive. No relationship was evident between the serologic responses and the number of lesions or the duration of infection.
The population survey revealed an overall seropositivity rate of 23%. The lowest antibody prevalence was in children aged 6 months to 2 years (3%), and seropositivity increased with age to reach 39% in persons >/=50 years old.
These findings indicate that MCV infections, including very mild or subclinical cases, may be more common in the general community than previously suspected.
DISEASE ASSOCIATIONS CHARACTERIZATION AIDS Int J Dermatol 1994;33:453-461
5-18% of patients
AXILLARY GRANULAR PARAKERATOSIS
- Incidental Granular Parakeratosis Associated With Molluscum Contagiosum.
Pock L, Cermakova A, Zipfelova J, Hercogova J.
From the *Dermatopathologic Laboratory, 2nd Medical Faculty, Charles University, Prague, Czech Republic; daggerDepartment of Dermatology, Znojmo; double daggerDepartment of Dermatology, Moravsky Krumlov; and section signDepartment of Dermatology and Venereology, 2nd Medical Faculty, Charles University, Prague, Czech Republic.
Am J Dermatopathol. 2006 Feb;28(1):45-47. Abstract quote
A patient presented with a 4-month history of slowly progressive pruritic papules on her trunk and extremities.
Biopsies from 2 of these lesions revealed molluscum contagiosum. One of the biopsies also showed several small foci of granular parakeratosis.
Based on the clinical features and course of this patient, the granular parakeratosis seems to be an incidental finding.
PATHOGENESIS CHARACTERIZATION Pox virus (Molluscipox genus)
Almost exclusively humans are infected
One case of chimpanzee and horse
Transmission Skin to skin including autoinoculation GENOME
The genome of molluscum contagiosum virus: analysis and comparison with other poxviruses.
Senkevich TG, Koonin EV, Bugert JJ, Darai G, Moss B.
Laboratory of Viral Diseases, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, Maryland 20892, USA.
Virology 1997 Jun 23;233(1):19-42 Abstract quote
Analysis of the molluscum contagiosum virus (MCV) genome revealed that it encodes approximately 182 proteins, 105 of which have direct counterparts in orthopoxviruses (OPV). The corresponding OPV proteins comprise those known to be essential for replication as well as many that are still uncharacterized, including 2 of less than 60 amino acids that had not been previously noted. The OPV proteins most highly conserved in MCV are involved in transcription; the least conserved include membrane glycoproteins. Twenty of the MCV proteins with OPV counterparts also have cellular homologs and additional MCV proteins have conserved functional motifs. Of the 77 predicted MCV proteins without OPV counterparts, 10 have similarity to other MCV proteins and/or distant similarity to proteins of other poxviruses and 16 have cellular homologs including some predicted to antagonize host defenses.
Clustering poxvirus proteins by sequence similarity revealed 3 unique MCV gene families and 8 families that are conserved in MCV and OPV. Two unique families contain putative membrane receptors; the third includes 2 proteins, each containing 2 DED apoptosis signal transduction domains. Additional families with conserved patterns of cysteines and putative redox active centers were identified. Promoters, transcription termination signals, and DNA concatemer resolution sequences are highly conserved in MCV and OPV.
Phylogenetic analysis suggested that MCV, OPV, and leporipoxviruses radiated from a common poxvirus ancestor after the divergence of avipoxviruses. Despite the acquisition of unique genes for host interactions and changes in GC content, the physical order and regulation of essential ancestral poxvirus genes have been largely conserved in MCV and OPV.
Molluscum contagiosum: recent advances in pathogenic mechanisms, and new therapies.
Smith KJ, Skelton H.
Department of Dermatology and Pathology, University of Alabama, Birmingham, Alabama, USA.
Am J Clin Dermatol 2002;3(8):535-45 Abstract quote
Two poxviruses, Molluscum contagiosum virus (MCV) and Variola virus are specific to humans. MCV is present worldwide and is directly passed by direct skin to skin contact to produce cutaneous and, rarely, mucosal lesions. It occurs predominantly in preadolescent children, sexually active adults, participants in sports with skin to skin contact, and in individuals with impaired cellular immunity.
MCV characteristically proliferates within the follicular epithelium, and with routine fixation produces an area of retraction artifact separating layers 1 to 3 of CD34+ stromal cells that immediately surround the follicle from the surrounding dermis. This feature may be obscured when the lesions are inflamed, usually after rupture into the surrounding dermis. MCV is a cytoplasmically replicating virus. MCV-infected cells grow in size, while internal organelles are dislocated and eventually obliterated by a large intracytoplasmic inclusion.
Rupture and discharge of the virus-packed cells occurs in a process similar to membrane debris and MCV accumulate in the crater-like ostium; MCV infection is spread by contact with infectious debris. In HIV-1-positive patients the histologic features, as well as the clinical features, may be atypical in patients with MCV infections. Not only are the lesions often large, but they may be verrucous and markedly hyperkeratotic.
Recent sequencing of the MCV genome has increased our understanding and investigations into its mechanisms for avoiding host defense mechanisms. These include regions which encode for homologues of cellular chemokines and chemokine-binding proteins, a homolog of MHC1 and a viral FLICE-like inhibitory protein.
Treatment, until recently, has depended upon tissue destruction including curettage, cryotherapy, CO(2) laser, electrodesiccation, trichloracetic acid and cantharadin. Recently, topical immune modulators have been used with some success. Understanding of the MCV genome is providing the basis for the development of drugs for therapy and prevention of MCV infections.
CHARACTERIZATION Laboratory Markers Serological Antibodies
Arch Dermatol 2000;136:1518-1522
Study of 508 patients with or without clinical infection
Antibodies present in 7/12 patients with MC (58%)
7/108 healthy controls (6%)
7/76 atopic dermatitis (9%)
7/39 with SLE (18%)
NOTE: No MC infection was noted in the latter 3 groups
1/7 HIV positive with MC (14%)
5/266 HIV positive without MC (2%)
POLYMERASE CHAIN REACTION
Identification and typing of molluscum contagiosum virus in clinical specimens by polymerase chain reaction.
Department of Infectious Diseases, Faculty of Medicine, University of Sydney, NSW, Australia.
J Med Virol 1997 Nov;53(3):205-11 Abstract quote
A polymerase chain reaction (PCR) which enables the detection of molluscum contagiosum virus (MCV) genomes in either fresh or formalin-fixed clinical specimens is described. The primers used were designed to amplify a 167 bp region of the 3.8 kbp HindIII fragment K of the MCV 1 genome.
The ability of this PCR to detect three common MCV types (1, 1v and 2) in clinical specimens was confirmed using frozen extracts from 75 molluscum lesions, and digests of single sections of 11 formalin-fixed, paraffin-embedded lesions; all of which had been previously typed by Southern hybridisation. In addition, 2 specimens previously negative by hybridisation were shown to be positive for MCV DNA by PCR. Confirmation of the identity of the PCR products and distinction between the two major MCV types (MCV 1/1v versus MCV 2) was achieved by comparison of the results of cleavage with the restriction endonucleases Hhal and Sacl. Sequencing of the PCR products revealed complete homology between MCV 1 and 1v, but minor nucleotide variations between MCV 1/1v and MCV 2 were identified.
As well as providing a highly sensitive means of diagnosis, the technique may also prove useful for investigations into the pathogenesis, epidemiology and natural history of molluscum contagiosum infection.
CLINICAL VARIANTS CHARACTERIZATION GIANT
Multiple giant molluscum contagiosa with cyst formation.
Egawa K, Honda Y, Ono T.
Department of Dermatology, Kumamoto University School of Medicine, Japan.
Am J Dermatopathol 1995 Aug;17(4):414-6 Abstract quote
We report a case of multiple cystic tumors distributed on the scalp, face, neck, and upper trunk of a 68-year-old male.
In all five cysts examined, the presence of molluscum contagiosum virus (MCV) was demonstrated electron microscopically, and the typical histological features of MCV infection were observed in the cyst wall. In one lesion, histological features suggesting a follicular origin of the cyst were seen.
HISTOLOGICAL TYPES CHARACTERIZATION General Large eosinophilic intranuclear bluish to eosinophilic inclusions VARIANTS
Molluscum Contagiosum: Histologic Patterns and Associated Lesions A Study of 578 Cases
Bernard Cribier, etal.
Am J Dermatopathol 2001;23:99-103 Abstract quote
Molluscum contagiosum (MC) is rarely associated with other skin diseases, especially cutaneous neoplasms. Such associations are exceptional and of unknown frequency.
The aim of this study was to record the histologic variants and frequency of associated lesions in a large series of consecutive MC cases.
We reviewed 578 MC cases from the Laboratory of Dermatopathology of the University Hospitals of Strasbourg, France (1959–1999).
The locations of MC were as follows: head and neck (34.7%), trunk (27.1%), lower limbs (20.7%), upper limbs (8.7%), and genitalia (3.8%). Molluscum contagiosum occurred more often in female patients (56.7%). The age range of patients included in this study was 0 to 19 years (34.9%), 20 to 39 years (31.1%), 40 to 59 years (22.8%), and over 60 years (6.5%). Histologic variants of MC were noted in 46 cases (31 pseudocystic, 8 giant, and 7 pedunculated). An underlying abscess was present in 65 cases. Of the 578 cases, 22 were associated with other lesions (3.8%). There were 9 cases of epidermal cysts, 4 of nevocellular nevi, 3 of metaplastic ossifications, 2 of true epidermal nevi, 2 of sebaceous hyperplasias, 2 of soft fibromas, and 1 of Kaposi sarcoma. Except in immunocompromised patients, such associations are likely to be coincidental. The clinical diagnosis was correct in 42.3% of the cases.
Clinical accuracy varied according to the age, localization, and histologic pattern of MC. Pseudocystic MC, giant MC, and MC associated with other lesions were responsible for frequent clinical misdiagnosis.
Counts and areas of S-100-positive epidermal dendritic cells in atypical molluscum contagiosum affecting HIV+ patients.
Vera-Sempere FJ, Rubio L, Massmanian A.
Service of Pathology, University Hospital La Fe, Medical School of Valencia University, Spain.
Histol Histopathol 2001 Jan;16(1):45-51 Abstract quote
Molluscum contagiosum is a common and self-limiting viral infection, that in HIV+ patients courses as an opportunist affection with atypical clinical features. Impaired cell-mediated immune response could be involved in such atypical growth.
We evaluated the density and area of Langerhans cells (LC) using S-100 immunohistochemistry in seven atypical molluscum contagiosum. LC density was quantified by three different methods using computer-assisted morphometry as well as estimating the relative area of LC with respect to epidermal area. Results were compared with two control groups (normal skin specimens and molluscum contagiosum affecting non-AIDS healthy patients). We found a virtual absence of LC in areas of molluscum lesions affecting both HIV+ and non-AIDS patients. Likewise we observed an evident decrease in LC density in perilesional epidermis of atypical molluscum with respect to both control groups. Upon comparing the counts and areas, we observed that this reduction in LC count was statistically significant only when considering LC related to length of basement membrane in atypical molluscum with respect to normal skin specimens. Our finding of a reduced number of LC in the perilesional epidermis of HIV+ patients with atypical molluscum could explain the high frequency and clinical challenge of molluscum contagiosum in immunocompromised people.
In spite of these results, further studies of LC kinetics and functions are required to precisely elucidate their role in the course of molluscum contagiosum in HIV+ patients.
Cutaneous pseudolymphoma in association with molluscum contagiosum in an elderly patient.
Moreno-Ramirez D, Garcia-Escudero A, Rios-Martin JJ, Herrera-Saval A, Camacho F.
Department of Dermatology, and Department of Pathology, Universitary Hospital Virgen Macarena, Seville, Spain.
J Cutan Pathol. 2003 Aug;30(7):473-5. Abstract quote
BACKGROUND: Molluscum contagiosum (MC) is a common cutaneous infection, which has been reported in association with cutaneous pseudolymphoma in few cases.
METHODS: A 72-year-old woman with a nodule arising on the external canthus was reviewed. The lesion was surgically removed, and the histopathological study demonstrated an epidermal invagination filled by molluscum bodies and a diffuse infiltrate comprising atypical lymphocytes.
RESULTS: Immunohistochemical stains disclosed predominance of T cells with positive CD30 labeling. Polymerase chain reaction failed to demonstrate clonal rearrangement of the T-cell receptor.
CONCLUSION: After ruling out systemic involvement, the patient was followed up for 2 years with no evidence of recurrence. We report this case to the best of our knowledge and discuss the literature about atypical clinical and histological presentations of MC.
Canthardin for treatement of childhood molluscum contagiosum
Silverberg, Sidbury, and Mancini
J Am Acad Dermatol 2000;43:503-7
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Last Updated February 22, 2006
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