Paronychia — Viva

Q1: Definition and nail unit anatomy (2 min)

What is paronychia? Where are the proximal and lateral nail folds, the eponychium (cuticle), the germinal matrix, the sterile matrix (nail bed) and the hyponychium (distal seal)? Which of these is the protective seal whose loss enables entry of organisms and irritants — and why does its loss matter for both acute and chronic paronychia?^[1][2]

Q2: Acute vs chronic paronychia — classification, organisms, course (3 min)

How would you distinguish ACUTE paronychia from CHRONIC paronychia at the bedside? State the duration cut-off (≤ 6 weeks acute vs > 6 weeks chronic), the dominant organism (Staphylococcus aureus 70-80% in acute; Candida + irritant contact dermatitis in chronic), the distribution (single finger vs multi-finger) and the hallmark (fluctuant pus lifting the cuticle vs loss of cuticle). Why is Candida in chronic paronychia a coloniser rather than the primary cause?^[1][2]

Q3: Differential diagnosis (3 min)

List the differentials and the discriminating features: herpetic whitlow (HSV-1/2, vesicles, burning pain, lymphangitis — DO NOT INCISE); felon (finger pulp abscess, different compartment, urgent I&D); green-nail syndrome (Pseudomonas / pyocyanin, green-black plate, onycholysis); periungual pyogenic granuloma (drug-induced EGFr / MEK / BTK inhibitors, friable bleeds); acrodermatitis continua of Hallopeau (sterile pustules of pustular psoriasis); nail-unit squamous cell carcinoma / melanoma (single-digit chronic disease — Hutchinson sign for melanoma). Which differentials are cannot-miss? (Felon, herpetic whitlow, necrotising fasciitis, nail-unit SCC / melanoma, flexor tendon sheath infection.)^[1][2]

Q4: Investigations (2 min)

What investigations would you arrange, and when? Acute paronychia is a clinical diagnosis; swab MCS if pus is obtained or treatment fails at 48-72 h. HSV PCR for herpetic whitlow (gold standard). Screen for diabetes (HbA1c), HIV, iron deficiency in recurrent / chronic disease. X-ray distal phalanx if bone pain or systemic signs (distal osteomyelitis). Biopsy for single-digit chronic disease (cancer).^[1][2]

Q5: Management — acute ladder (3 min)

Outline the staged ladder for acute paronychia: (1) warm saline soaks 3-4× daily + topical antibiotic (mupirocin / fusidic acid) for early disease without pus; (2) incision along the longitudinal axis of the cuticular edge with the sharp tip of a #11 blade or an 18G needle, lifting the cuticle from the plate to release pus, send pus for MCS — do NOT incise deeply into the nail bed (matrix scar risk); (3) partial nail-plate avulsion ≤ 25% for subungual extension; (4) oral flucloxacillin 500 mg QDS 5-7 days for surrounding cellulitis / systemic features; (5) escalation to IV flucloxacillin 1-2 g 6-hourly ± clindamycin if severe. Mark the border for 48-72 h reassessment.^[1][2]

Q6: Management — chronic ladder (3 min)

Outline the four-pillar chronic-paronychia ladder: (1) dry-work directives (cotton-lined rubber gloves, SLS-free cleanser, emollient, barrier cream); (2) topical anti-inflammatory — tacrolimus 0.1% ointment BD × 6 weeks (steroid-sparing first-line, Rigopoulos 2009 BRJ Dermatol RCT vs betamethasone — equivalent efficacy, no atrophy) OR clobetasol propionate 0.05% BD × 2-4 weeks; (3) antifungal / antibacterial adjunct — topical clotrimazole or oral fluconazole 50 mg OD × 3-6 weeks (or 150 mg weekly pulse) / itraconazole 200 mg BD pulse week/month × 2 for candidal culture-positive disease; oral doxycycline 100 mg BD × 6-12 weeks for bacterial inflammatory component; (4) eponychial marsupialisation for refractory disease. Set patient expectation: nail regrowth 3-6 months (fingers) / 12-18 months (toes); recurrence 30-50% if wet-work resumed.^[1][2]

Q7: Drug-induced paronychia (2 min)

Which drug classes cause paronychia or periungual pyogenic granuloma? (Retinoids — isotretinoin, acitretin; EGFr antibodies — cetuximab, panitumumab; EGFr TKIs — osimertinib, gefitinib, erlotinib, dacomitinib, amivantamab; MEK inhibitors — trametinib, cobimetinib; BTK inhibitors — ibrutinib, acalabrutinib; antiretrovirals — indinavir, lamivudine; taxanes — docetaxel; mTOR inhibitors.) What's the bedside clue? (Periungual pyogenic granuloma — friable, bleeds on contact.) Management: oncology liaison for dose modification; topical clobetasol + silver nitrate cautery + topical timolol 0.5% gel; avoid systemic retinoids.^[1][2]

Q8: Complications, prognosis and special populations (2 min)

What are the local complications (subungual abscess, matrix damage, lateral fold hypertrophy, distal phalanx osteomyelitis, flexor tendon sheath infection with Kanavel signs, nail-unit SCC / melanoma misdiagnosed for years)? What are the systemic complications (bacteraemia, metastatic infection, necrotising fasciitis in elderly diabetics — mortality up to 30%)? List the special-population deltas: paediatric (weight-based dosing, avoid minocycline / doxycycline <12 y); pregnancy (β-lactams safe, avoid doxycycline / retinoids / fluoroquinolones, aciclovir safe); elderly (avoid prolonged tetracyclines per Beers, avoid fluoroquinolones for tendonopathy / aortic dissection); immunocompromised (broader differential — atypical mycobacteria, Bartonella, deep fungi).^[1][2]

Q9: Regional deltas and evidence (2 min)

State the UK NICE CKS first-line (oral flucloxacillin 500 mg QDS 5-7 days; clarithromycin for penicillin allergy); the IDSA 2014 MRSA-cover trigger (CA-MRSA prevalence > 20% in purulent SSTI); the Australia eTG chronic-paronychia cornerstone (wet-work avoidance is the foundation; topical tacrolimus first-line); the ICMR / Indian empirical (amoxicillin-clavulanate 625 mg TDS 5-7 days for acute paronychia; fluconazole 150 mg weekly pulse for chronic candidal paronychia; barefoot-walking + agricultural exposure and HIV-related paronychia are higher). Quote the Rigopoulos 2009 / 2010 BR J Dermatol RCT — tacrolimus 0.1% vs betamethasone valerate 0.1% — equivalent efficacy in chronic paronychia, with tacrolimus steroid-sparing and not atrophogenic. Cite the Lin 2021 Cochrane and Ibler 2014 on recurrent furunculosis / recurrent acute paronychia — bundle of decolonisation + diabetes screen + hygiene.^[1][2]

References3ShowHide

1. [1]Leggit JC Acute and Chronic Paronychia Am Fam Physician, 2017.PMID 28671378
2. [2]Bahunuthula RK, Thappa DM, Kumari R, et al. Evaluation of role of Candida in patients with chronic paronychia Indian J Dermatol Venereol Leprol, 2015.PMID 26087081
3. [3]Fowler JR, Ilyas AM Epidemiology of adult acute hand infections at an urban medical center J Hand Surg Am, 2013.PMID 23647640