Understanding Chickenpox in Adults: A Detailed Case Study from Massachusetts General Hospital

Table of Contents

• Case Presentation: The Patient's Story
• Physical Examination Findings
• Differential Diagnosis: What Could It Be?
• How Homelessness Affects Skin Health
• Parasitic Infection Possibilities
• The Danger of Diagnostic Bias
• Viral Infection Considerations
• Final Diagnosis and Testing
• Treatment and Public Health Implications
• Source Information

Case Presentation: The Patient's Story

A 56-year-old woman arrived at the emergency department with a sore throat and widespread rash that had developed over two days. She reported intense itching (pruritus) on her chest but hadn't inspected her skin until noticing facial lesions in a mirror while using a public bathroom.

The patient lived in a homeless shelter and noted that several other residents had been scratching themselves recently. She had heard shelter employees discussing lice and scabies but had no exposure to new soaps, detergents, or outdoor environments. Her medical history included depression with psychosis, dyslipidemia (high cholesterol), and metabolic dysfunction-associated steatohepatitis (a type of liver disease).

Her medications included risperidone (an antipsychotic) and benztropine (used to treat side effects of antipsychotics). She had no fever, breathing difficulties, or neurological symptoms, which helped narrow down the possible causes of her condition.

Physical Examination Findings

Upon examination, the patient had a temperature of 38.4°C (100.1°F), indicating a low-grade fever. Her other vital signs were normal: blood pressure 134/72 mm Hg, pulse 83 beats per minute, respiratory rate 16 breaths per minute, and oxygen saturation 96% on room air.

The skin examination revealed several important findings:

• Diffuse pink papules (small raised bumps) on the forehead, nose, cheeks, and chin
• An ulcer on the anterior upper gum
• Excoriated (scratched) papules and vesicles (fluid-filled blisters) on the back, chest, and abdomen
• Involvement of skin folds beneath the breasts (inframammary) and groin (inguinal)
• Pink papules on the backs and palms of the hands

Laboratory tests showed mildly elevated liver enzymes: aspartate aminotransferase 44 U/L (normal range 9-32) and alanine aminotransferase 60 U/L (normal range 7-33). The white blood cell count was 5,300 cells per microliter with 5.3% atypical lymphocytes (abnormal white blood cells sometimes seen in viral infections).

Differential Diagnosis: What Could It Be?

The medical team considered multiple possible causes for the patient's symptoms. Given her living situation in a homeless shelter and reported itching, parasitic infections were initially considered. However, the presence of vesicles (blisters), facial involvement, and oral ulcers suggested other possibilities needed evaluation.

The diagnostic process required careful consideration of how her homelessness might affect her risk for various conditions while avoiding the cognitive bias of focusing only on conditions common in marginalized populations.

How Homelessness Affects Skin Health

People experiencing homelessness face significantly higher rates of skin conditions due to limited access to hygiene facilities, communal living environments, and barriers to healthcare. Shared spaces and bedding increase the risk of parasitic infestations, while chronic conditions like eczema and psoriasis often go untreated.

Substance use, particularly injection drug use, can increase susceptibility to skin infections. Communicable diseases including respiratory, gastrointestinal, and sexually transmitted infections spread more quickly in homeless populations, especially those in shelter environments.

These factors made parasitic infestations an important initial consideration, but the medical team recognized they needed to look beyond these common conditions to make an accurate diagnosis.

Parasitic Infection Possibilities

The medical team evaluated three main parasitic possibilities:

Scabies: Caused by the Sarcoptes scabiei mite, this condition typically causes burrows, red papules, and excoriations in web spaces between fingers, wrists, ankles, armpits, genitals, and around the navel. The prevalence ranges from 0.18% to 76.9% across different populations, with higher rates in developing countries and displaced populations. While scabies was plausible given the itching and shelter exposure, the facial involvement and vesicles were unusual features.

Crab Lice: These parasites typically attach to hair shafts in the pubic region, armpits, eyelashes, and beard. They affect 0.3-4.6% of the global population, with approximately 2% prevalence in adults. However, they wouldn't cause a generalized rash or vesicles, making this diagnosis unlikely.

Body Lice: Strongly associated with homelessness, body lice infestation prevalence ranges from 19.1% to 68.0% among homeless individuals. The lice live in clothing seams and move to skin to feed, causing itchy papules and excoriations. While the diffuse papules could fit this diagnosis, the vesicular component and facial involvement were atypical.

The Danger of Diagnostic Bias

The medical team specifically discussed anchoring bias - the cognitive tendency to focus on initial prominent features without adjusting as new information emerges. This bias can be particularly problematic when evaluating marginalized populations, potentially widening healthcare disparities.

In this case, focusing only on parasitic infections because of the patient's homelessness could have delayed diagnosis of other conditions, particularly if her rash was caused by an infection that could spread to others. Recognizing this potential bias was crucial for accurate diagnosis.

Viral Infection Considerations

The team evaluated several viral possibilities that could explain the patient's symptoms:

Measles: Although measles incidence is increasing globally (with an estimated 10.3 million cases in 2023), the patient's rash didn't show the characteristic coalescing patches or bluish-white mouth spots (Koplik spots) typical of measles. A ongoing outbreak in West Texas had reached 327 cases across 15 counties with 40 hospitalizations and one death as of March 25, 2025.

Rubella: This typically causes a milder measles-like rash with postauricular lymph node swelling, but the presence of vesicles and oral ulcers wasn't consistent with rubella.

Acute HIV Infection: Up to 80% of new HIV infections cause acute retroviral syndrome with fever, muscle aches, sore throat, and rash. However, the patient didn't have the characteristic widespread rash or multiple symptoms associated with primary HIV infection.

Herpes Simplex Virus (HSV): Typically causes localized blister clusters rather than widespread distribution. Disseminated HSV can occur in immunocompromised people but was unlikely given her lack of known immune deficiency.

Mpox: Causes characteristic deep-seated, well-circumscribed, umbilicated lesions that didn't match this patient's rash pattern.

Varicella-Zoster Virus (VZV): The combination of vesicles, oral ulcers, polymorphic lesions (different stages simultaneously), and elevated liver enzymes pointed toward chickenpox (primary VZV infection), which is rare in adults but can cause severe disease.

Final Diagnosis and Testing

Doctors performed a skin biopsy from the right chest area, which revealed definitive evidence of VZV infection:

• Vesicular and acantholytic changes in the epidermis and hair follicles
• Marked epidermal necrosis (tissue death)
• Viral cytopathic effects including multinucleation, nuclear molding, and chromatin margination
• Strong positive immunohistochemical staining for VZV
• Negative staining for HSV-1 and HSV-2

Nucleic acid testing confirmed VZV DNA in the skin sample while ruling out herpes viruses. Bacterial culture grew only normal skin flora (Cutibacterium acnes). Serologic testing showed no detectable VZV IgM or IgG antibodies, confirming this was a primary infection with no previous exposure or immunity.

The absence of detectable antibodies suggested the blood test was performed before the immune system had developed a measurable response, which typically takes 2-5 days after rash appearance. VZV IgM antibodies peak at 2-3 weeks then decline rapidly, usually becoming undetectable within one year.

Treatment and Public Health Implications

The diagnosis of chickenpox in an adult carries significant implications for both treatment and infection control. Although chickenpox is typically considered a childhood illness, adults who contract it face higher risks of severe complications including hepatitis and pneumonitis.

Effective management requires three crucial steps: identification, isolation, and information sharing. Given the high transmissibility of VZV, strict infection control measures were implemented:

• Placement in a negative-pressure isolation room
• Airborne and contact precautions
• Healthcare personnel used fit-tested respirators, gowns, and gloves

The case highlights several important points for patients and healthcare providers. First, while over 95% of adults born in the U.S. before 1980 have had chickenpox and are immune, some remain susceptible. Second, childhood vaccination with two doses of varicella vaccine is approximately 95% effective at preventing clinical disease, dramatically reducing childhood cases but potentially making clinicians less familiar with adult presentations.

VZV transmission occurs through direct contact with skin lesions or inhalation of respiratory droplets. Aerosolization from skin lesions can also occur, necessitating strict isolation precautions. Although second episodes of chickenpox are rare, they can occur even in immunocompetent individuals.

This case also demonstrates the importance of considering uncommon presentations of common illnesses, particularly in marginalized populations who may be subject to diagnostic biases. The approximately 24-hour delay in recognition underscores the need for maintained clinical vigilance even for conditions that have become less common due to successful vaccination programs.

Source Information

Original Article Title: Case 12-2025: A 56-Year-Old Woman with Sore Throat and Rash

Authors: John Trinidad, M.D., M.P.H.; Kimon C. Zachary, M.D.; Ting Zhao, M.D.

Publication: The New England Journal of Medicine, April 24, 2025; 392:1637-45

DOI: 10.1056/NEJMcpc2412522

This patient-friendly article is based on peer-reviewed research from Massachusetts General Hospital's Case Records series.