What are the common sites of occurrence for herpes zoster in adults, particularly those over 50 years old with weakened immune systems?

Herpes Zoster Sites of Occurrence

Primary Distribution Pattern

Herpes zoster most commonly affects the thoracic dermatomes (56% of cases), followed by cranial nerves (13-20%), lumbar (13%), cervical (11%), and sacral nerves (4%). 1, 2

Detailed Anatomical Distribution

Thoracic and Abdominal Region

• The thoracic and abdominal dermatomes represent the most frequent site of herpes zoster occurrence, accounting for over half of all cases 1
• This predominance reflects the large number of thoracic ganglia where varicella zoster virus remains latent 2

Cranial Nerve Involvement

• Cranial nerves are affected in 13-20% of herpes zoster cases, with the trigeminal and facial nerves being the most commonly involved 1, 3
• Among cranial nerve involvement, herpes zoster ophthalmicus (HZO) affects approximately 4-20% of all herpes zoster patients, representing involvement of the ophthalmic division (V1) of the trigeminal nerve 3
• The first division (ophthalmic) of the trigeminal nerve is most commonly affected, while the second (maxillary) and third (mandibular) divisions are rarely involved 1, 4
• Approximately 50% of patients with HZO develop ocular complications, including conjunctivitis, keratitis, and uveitis 5, 3

Cervical, Lumbar, and Sacral Distribution

• Cervical dermatomes account for 11% of cases 1
• Lumbar dermatomes represent 13% of cases 1
• Sacral nerves are the least commonly affected at 4% 1

Special Considerations for High-Risk Populations

Adults Over 50 Years

• The incidence and severity of herpes zoster increase substantially with age, making older adults the highest-risk population 2
• Vaccination with recombinant zoster vaccine (Shingrix) is strongly recommended for all adults 50 years or older to prevent herpes zoster and its complications 5, 6

Immunocompromised Patients

• Immunocompromised adults aged 19 years and older should receive herpes zoster vaccination due to their elevated risk of reactivation 5
• Atypical presentations, including multidermatomal involvement, may occur more frequently in immunocompromised individuals, though rare cases have been reported in immunocompetent patients 7

Clinical Pitfalls and Caveats

• Maxillary nerve involvement can present with odontalgia as the only prodromal symptom, potentially leading to diagnostic confusion with dental pathology 1, 4
• Multidermatomal involvement of the trigeminal nerve, though rare in immunocompetent patients, should prompt evaluation for underlying immunodeficiency 7, 4
• Herpes zoster ophthalmicus requires urgent ophthalmologic consultation due to the risk of vision-threatening complications in up to 25% of affected patients 3