Clinical Impression: Herpes Zoster (Shingles) — likely with secondary bacterial superinfection

• Sudden onset within hours (evening onset, seen next day) — classic for VZV reactivation, which erupts abruptly after a day or two of prodromal pain/tingling
• No itching — a genuinely useful negative here. Zoster classically causes burning pain, hyperesthesia, or paresthesia, not pruritus, which helps distinguish it from contact dermatitis, scabies, or an allergic/insect-bite eruption
• 54-year-old with diabetes mellitus — DM is a well-documented risk factor for herpes zoster reactivation and for more severe/disseminated disease, because it impairs cell-mediated immunity (- Andrews' Diseases of the Skin, Ch. Varicella-Zoster Virus). A 2024 systematic review/meta-analysis of zoster risk factors (PMID 38236326) also confirms diabetes as a consistently reported risk factor.
• Leukocytosis (WBC 18,000) and elevated ESR (35) — higher than what uncomplicated zoster alone typically produces. In a diabetic, this pattern raises real suspicion for secondary bacterial superinfection of the vesicles/pustules (Staph aureus/Strep pyogenes), which diabetics are prone to given impaired neutrophil function and microvascular disease.

Key differentials to actively exclude on exam

Suggested work-up

• Confirm dermatomal distribution with full exposure of the limb/trunk (check for band-like pattern, any lesions on back matching same segment)
• Tzanck smear or VZV PCR from vesicle fluid if diagnosis uncertain
• Swab/culture of any purulent lesions given the leukocytosis, to guide antibiotics if superinfected
• Random/fasting glucose optimization — FBS 166 mg/dL is only mildly elevated but glycemic control affects healing and zoster severity
• No urgent need for HIV/immunosuppression workup at 54 with known DM/HTN unless exam shows multidermatomal or disseminated disease

Management

1. Start antiviral therapy promptly (within 72 hours of onset — well within window since this began yesterday evening):
   • Valacyclovir 1 g PO three times daily for 7 days, or
   • Acyclovir 800 mg PO five times daily for 7-10 days (Renal dose adjustment as needed; check renal function given age/DM/HTN)
2. If clinical signs of bacterial superinfection (purulent discharge, spreading erythema/warmth, disproportionate WBC/ESR) — add an antistaphylococcal antibiotic (e.g., cephalexin or cloxacillin) pending culture
3. Analgesia — NSAIDs or paracetamol; consider gabapentin/pregabalin early if pain is significant, since diabetes is itself a risk factor for postherpetic neuralgia
4. Local care — keep lesions clean and dry, avoid occlusive dressings, monitor for expanding cellulitis
5. Glycemic optimization — tighter control supports healing and immune response
6. Review in 48-72 hours to confirm response to antivirals and resolution/no progression of pustules

Quick Treatment Plan — Herpes Zoster (± bacterial superinfection) in a diabetic

• Valacyclovir 1 g PO TID x 7 days, or
• Acyclovir 800 mg PO 5x/day x 7-10 days (adjust dose if renal impairment)

• Add antistaphylococcal antibiotic — Cephalexin 500 mg PO QID x 7 days, or Cloxacillin 500 mg QID
• Swab for culture before starting if possible

• Paracetamol ± NSAID (caution with HTN/renal status)
• If pain significant: Gabapentin 100 mg OD-BD, titrate up (diabetic = higher PHN risk)

• Keep lesions clean and dry, calamine or plain antiseptic lotion, avoid occlusive dressing
• No itching so no need for antihistamines

• Optimize DM control (FBS 166 — review/adjust oral hypoglycemic dose)
• Continue HTN medications as usual

• Review in 48-72 hrs for response, watch for new dermatomes/dissemination or worsening cellulitis

• Ampicillin-Sulbactam 1.5-3 g IV q6-8h — covers MSSA, streptococci, and anaerobes (- Washington Manual of Medical Therapeutics; Harrison's Principles of Internal Medicine, Cellulitis section)
• Cefoperazone-Sulbactam 1.5-3 g IV q12h (the more commonly used "Sulbactam" injectable in Indian practice, e.g., Magnex/Zosul) — broader gram-negative cover in addition to gram-positive, useful if there's any suspicion of mixed/gram-negative involvement in a diabetic (- Swanson's Family Medicine Review; Goodman & Gilman's Pharmacological Basis of Therapeutics)

• Either is appropriate empirically while awaiting culture/sensitivity from the pustules if you swab them
• This treats the bacterial component only — continue the antiviral (Acyclovir/Valacyclovir) alongside for the underlying zoster; sulbactam combinations have no antiviral activity
• Check renal function before dosing (relevant given his age and diabetes) and adjust interval if creatinine clearance is reduced
• Switch to oral once clinically improving (afebrile, WBC trending down, no progression) — usually after 48-72h of IV therapy, completing a total 7-10 day course