Case 1 introduction

A 42-year-old woman presents to the office for a routine gynecologic exam. She is feeling well and has no specific complaints at this visit. While reviewing your records, you see that she has not come in for a Pap smear in about 5 years. She admits that she has not come in because she has been feeling fine and didn't think it was really necessary. She has a history of three pregnancies resulting in three full-term vaginal deliveries of healthy children. She was treated at the age of 22 for chlamydia. She has never had an abnormal pap smear. Her social history is notable for a one-pack per day smoking history for the past 25 years. She is divorced from her first husband and is sexually active with a live-in boyfriend for the past 3 years. She has had 7 sexual partners in her lifetime. Her examination today is normal. You perform a Pap smear as part of the examination. The report arrives 10 days later with the diagnosis "high-grade squamous intraepithelial lesion."

 What is the most likely infectious etiology of this lesion?

 What specific virus types confer a high risk of cervical neoplasia?

 Where on a cellular level does this organism tend to replicate in benign diseases? In malignancies?

ANSWERS TO CASE 30: Human Papillomavirus

 Most likely infectious etiology of this lesion: human papillomavirus (HPV)-related infection.

 Specific virus types confer a high risk of cervical neoplasia: HPV types 16 and 18 are most commonly associated with anogenital neoplasias.

 Location of replication in benign diseases and malignancies: The site of replication in benign HPV infections occurs in the host neoplasm where the viral DNA remains extrachromosomal. However, in HPV-related malignancies the viral DNA is integrated into the host genome.

Human papillomavirus (HPV) preferentially infects the squamous epithelium of skin and mucous membranes causing epithelial proliferation and the development of cutaneous warts and genital, oral, and conjunctival papillomas. Although most HPV infections are benign, and most warts or lesions regress spontaneously with time, some HPV viral types have been shown to be linked to cervical and anogenital carcinomas (Table 30-1).

HPV gains entry through breaks in the skin and replicates in the basal cell layer of the epithelium. HPV DNA is replicated, and the viral particles are assembled in the nucleus of epithelial cells with late viral gene expression occurring in the upper layers of differentiated keratinocytes. In benign lesions, such as common skin warts, the viral DNA remains extrachromosomal in the nucleus of the infected epithelial cell. However, more commonly in carcinomas or high-grade intraepithelial lesions viral DNA becomes integrated into the host genome. The viral genome encodes transforming genes, which have been shown to cause the inactivation of proteins that inhibit cellular growth, making infected cells more susceptible to mutation or other factors that may lead to the development of dysplasia and cancer.

HPV DNA, primarily types 16 and 18, has been shown to be present in more than 95 percent of cervical carcinoma specimens. Because of their high occurrence in cervical cancers, these HPV types are considered to be high-risk, whereas HPV types 6 and 11 are considered low-risk and many other HPV types are considered benign. Yet, because many HPV-related infections (even those with types 16 and 18) are benign with lesions that can regress spontaneously, the utility of characterizing specific HPV types in clinical specimens remains to be determined.

Diagnosis

HPV infection presents clinically with the growth of a variety of cutaneous warts and papillomas. Warts result from HPV replication stimulating excessive growth of the epidermal layers above the basal layer (Figure 30-1). Different types of warts (flat, plantar, or common), genital condylomas, and laryngeal papillomas can develop depending on the infecting viral type and the site of infection. Laryngeal papillomas can occur in infants born to mothers with active HPV genital lesions. While rare, these papillomas often require repeated surgical removal. Anogenital warts occur on the squamous epithelium of the external genitalia and anorectum and are most commonly caused by HPV types 6 or 11, however, these lesions rarely undergo malignant transformation. HPV types 16 and 18 are responsible for most cases of cervical intraepithelial neoplasia and cancer. Cervical cancer usually develops after a progression of cellular changes from cellular atypia to low-grade intraepithelial lesion, high-grade intraepithelial lesion and subsequently to carcinoma. Although the mechanisms of host defenses against HPV are not well understood, the immune system, especially cellular immunity, are important in the control of HPV infections. HPV diseases occur more frequently and tend to be more severe in immunocompromised hosts.

Although many HPV infections are benign with the resulting warts or lesions regressing spontaneously with time, because of the strong association of HPV with cervical carcinomas and transmission via vaginal delivery, physical treatment

and removal of lesions is often performed. Physical treatment of warts and other lesions involves local cellular destruction by means of cryotherapy, acid application or electrocautery. Alternatively, immune stimulant therapy is used to promote immunologic clearance of the abnormal cells using either the injection of interferon or topical applications of imiquimod. Cervical cancer usually develops after a progression of cellular changes from cellular atypia to low-grade intraepithelial lesion, high-grade intraepithelial lesion, and subsequently to carcinoma. The introduction of routine screening of women for cervical cancer with Papanicolaou (Pap) smears has resulted in finding more abnormalities in earlier, more treatable stages, and a marked reduction in the death rate from cervical cancer. Most deaths from cervical cancer now occur in women who have not had adequate Pap smear screening. Research on HPV-vaccine development is ongoing. A prospective study of an HPV-16 virus-like particle vaccine has indicated the potential for prevention of persistent infection with the HPV type 16. Infection with HPV can be prevented by avoiding direct contact with infected skin lesions. Sexual transmission of HPV can be prevented by safe sex practices.

COMPREHENSION QUESTIONS

[30.1] Which of the following types of cancers is HPV most commonly associated with?

[30.2] HPV-related cervical intraepithelial neoplasia can be diagnosed by the presence of which of the following histologic features?

[30.3] Which of the following viral families is known to be causally associated with tumor formation in healthy appearing human adults?

[30.1] A. of the types of cancers listed, HPV is most commonly associated with anogenital carcinomas, which includes cervical carcinomas.

[30.2] D. HPV produces characteristic cytoplasmic vacuolization and nuclear enlargement of squamous epithelial cells, referred to as koilocytosis; answers A, B, C, and E are incorrect: Both Cowdry type A intranuclear inclusions and enlarged multinucleated cells can be seen with herpes simplex virus (HSV) and varicella-zoster virus (VZV) infections; central, basophilic intranuclear inclusion bodies are seen in CMV infections, whereas the presence of atypical lymphocytes is seen specifically in Epstein-Barr virus (EBV) infections.

[30.3] B. HPV is a member of the Papovavirus family and is causally associated with cervical cancer in otherwise healthy individuals; answers A, C, D, and E are incorrect: Hepatitis C virus is a member of the Flaviviruses family and causes chronic hepatitis and in severe cases is a factor in liver cancer development; Paramyxoviruses include agents such as respiratory syncytial virus and measles virus and are not associated with carcinomas; human polyoma viruses include BK and JC viruses, which have been associated with immunocompromised patients, and their role in formation of human tumors is still under investigation.

A 4-year-old girl is brought in by her mother for the evaluation of multiple skin growths on her neck and upper chest. They have been present for a month or two. They are not pruritic or painful. The mother thinks that they are "pimples" because she squeezed a couple of them and some white material was expressed. She has been treating the lesions with an over-the-counter acne preparation, but it hasn't helped. The child has no significant medical history, takes no medications, and has no allergies. On examination you see multiple discrete, isolated 1-2 mm papules on her upper chest and lower neck. They are flesh colored, have a central umbilication, and feel firm on palpation. The remainder of her examination is normal. You suspect Molluscum contagiosum.

 How did the girl most likely acquire this infection?

 What would you see microscopically on a stained slide of material expressed from the core of one of these lesions that would confirm your diagnosis?

 Most likely mechanism of acquisition of infection: Direct contact with the virus or via contact with contaminated fomites.

 Microscopic findings of expressed material confirming diagnosis: Microscopic observation of the core material would show eosinophilic cytoplasmic inclusions, also known as molluscum bodies.

Summary: A 4-year-old girl with multiple discrete 1-2 mm papules on her upper chest and lower neck that are flesh colored, have a central umbilication, consistent with Molluscum contagiosum.

CLINICAL CORRELATION

Introduction

Molluscum contagiosum is a poxvirus that causes benign cutaneous disease worldwide. It is transmitted via direct contact with infected cells or with objects contaminated with virus particles. It causes small wart-like growth on infected skin, and occurs more frequently in children than adults.

Because the worldwide eradication of smallpox has been documented, Molluscum contagiosum is the only poxvirus specific for humans. Viral inoculation occurs through small skin abrasions, either from direct contact with infectious particles or via contaminated fomites. The incubation period for Molluscum contagiosum infection is approximately 2 weeks to 6 months. Some documented forms of viral spread include direct contact with lesions during wrestling matches, in swimming pools, sharing of towels, and sexual contact. Molluscum contagiosum infection is more common in children than in adults, and in adults it is most often transmitted by sexual contact. Immunocompromised persons who are infected with Molluscum contagiosum may develop hundreds of lesions. Patients who are at greatest risk for this presentation are those with late-stage AIDS, with a CD4 count  200 cells/microliter.

Molluscum contagiosum clinically causes discrete, flesh-colored papules with a central umbilication. These nodular lesions most commonly form in groups of 5-25 occurring on the trunk, genitalia, and extremities. They are also known to cause "kissing lesions" via direct contact of a lesion with an uninfected area of skin on the same host; such as a lesion on the lateral chest may cause a "kissing lesion" on the inner arm. The semisolid core of these lesions can be expressed and examined microscopically for the presence of large, eosinophilic inclusions, known as molluscum bodies.

The lesions of Molluscum contagiosum generally develop within 2-3 months of contact and usually resolve within 1-2 years. Cell-mediated and humoral immunity both appear to be important for disease resolution. When indicated, the lesions can be removed by curettage, electrocautery, or liquid nitrogen applications.

[31.1] The incidence of Molluscum contagiosum as a sexually transmitted disease is increasing in young adults and results in the formation of small wartlike lesions in the genital region. Which of the following viruses might also be suspected in such a case of sexually acquired lesions?

[31.2] Which of the following statements best describes the viral characteristics of Molluscum contagiosum?

[31.3] A sexually active 17-year-old man presents to the local free clinic to check some small papules that appeared on his penis. The papules are small and white and contain a central depression in their center. There is no penile discharge, nor is there pain on urination. To what group is the organism most likely associated with?

[31.1] C. Human papillomavirus; answers A, B, and D are incorrect; Cytomegalovirus is known as a sexually transmitted disease but does not characteristically form lesions in or around the genitalia; varicella-zoster virus does form vesicular lesions but appears clinically as a vesicular rash of the head, trunk, or extremities in a dermatomal pattern, not as a genital infection; human immunodeficiency virus is also known to be transmitted via sexual contact, yet it manifests clinically primarily through suppression of the host immune response, not through the formation of genital lesions.

[31.2] B. Molluscum contagiosum is a poxvirus and therefore is a double-stranded DNA virus encoding a DNA-dependent RNA polymerase; answers A, C, D, and E are incorrect: (A) describes the characteristics of rabies virus; (C) more appropriately describes herpes simplex viruses; (D) poxviruses do replicate in the host cytoplasm, and Molluscum contagiosum is a double-stranded DNA virus; (E) more appropriately describes human papillomaviruses.

[31.3] A. The disease in question is Molluscum contagiosum, which belongs to the Poxviridae and is characterized by small white papules with a central umbilication usually found in the genital region; answers B, C, D, and E are incorrect: (B) Papovaviridae include human papillomavirus and BK, JC polyomavirus, and although HPV causes genital warts, they do not have the central umbilication present in Molluscum contagiosum; (C) Adenoviridae include a variety of viral serotypes which cause respiratory, ocular, and gastrointestinal diseases; (D) Parvoviridae include erythema infectiosum characterized by the slapped cheek appearance; (E) Arenaviridae include lymphocytic choriomeningitis and Lassa virus, which are not described in the question stem.

A 6-year-old boy is brought to your office for evaluation of fever, ear pain, and swollen cheeks. His mother reports that he's had 3 or 4 days of low-grade fever and seemed tired. Yesterday he developed the sudden onset of ear pain and swelling of the cheeks along with a higher fever. He is an only child, and neither of the parents has been ill recently. He has had no significant medical illnesses in his life, but his parents decided not to give him the measles, mumps, rubella (MMR) vaccine because they read that it could cause autism. On examination, his temperature is 38.6C (101.5F), and his pulse is 105 beats per minute. He has swollen parotid glands bilaterally to the point that his earlobes are pushed up, and the angle of his mandible is indistinct. His tympanic membranes appear normal. Opening his mouth causes pain, but the posterior pharynx appears normal. You do note some erythema and swelling of Stensen duct. He has bilateral cervical adenopathy.

 What is the cause of this child's illness?

 What factor has reduced the incidence of this disease by over 99 percent in the United States?

 Most likely cause of this child's disease: Mumps virus.

 Factor decreasing disease incidence by over 99 percent in the United States: Routine vaccination with live, attenuated mumps virus.

Summary: A 6-year-old boy with has tender inflammation of the parotid glands (parotitis) and fever.

CLINICAL CORRELATION

Introduction

The mumps virus is primarily a childhood disease that causes acute, painful swelling of the parotids and other glands. It is a highly communicable disease that has one known serotype and infects only humans. Mumps is endemic around the world, with approximately 90 percent of children being infected by the age of 15. It is now an uncommon illness in countries such as the United States, where a live attenuated vaccine is widely used. The MMR vaccine, a combination vaccine of measles, mumps, and rubella, has resulted in a greater than 99 percent reduction in the incidence of mumps. Almost all cases of mumps now seen are in the unvaccinated or in persons with depressed cellular immunity.

 Be able to describe the characteristics of the mumps virus.

The mumps virus is a member of the genus Rubulavirus of the family Paramyxoviridae. It is an enveloped, spherical virus with a single-stranded, negative-sense RNA genome. The viral envelope contains two glycoproteins: a hemagglutinin-neuraminidase protein involved in attachment and a membrane fusion protein. The mumps virus is transmitted to epithelial cells of the mouth or nose via direct contact with contaminated respiratory droplets or saliva or via fomites. The virus then fuses with the host cell membrane via the specific viral attachment and surface fusion proteins, which results in binding to sialic acid on the target cell membrane. Transcription, replication, protein synthesis, and assembly occur in the cytoplasm of the host cell. Newly formed virions acquire their outer envelope by budding through the host cell membrane and are released to infect other host cells. After initial infection and replication in the nasal or upper respiratory tract, viral infection spreads to the salivary glands. Virus infects the parotids or other salivary glands either by ascending infection into the gland through Stensen duct or by viremia. Viral particles are also transmitted to distant organs, such as the kidneys, testes, ovaries, and central nervous system (CNS) through viremic spread.

The symptoms of mumps are often the result of the inflammatory response of the host immune system. Many mumps infections are subclinical, and this, along with the fact that infected persons are contagious even 1-2 weeks prior to developing symptoms, promotes person-to-person spread of the disease. The cell-mediated immune system is responsible for defense against this infection and acquired immunity is lifelong. Passive immunity is transferred from mothers to newborns, and thus, mumps is rarely seen in infants less than 6 months old.