A patient presents with acute onset pain and swelling around the nail of the middle finger, as shown in the image. Which of the following is the most likely diagnosis?

Explanation

## Image Findings * **Erythema (redness)** and **swelling** of the proximal and lateral nail folds of the middle finger. * Evidence of a **purulent collection (pus)** beneath the nail fold, particularly at the proximal aspect, causing elevation of the cuticle. * The inflammation is localized to the periungual tissues. ## Diagnosis **Key Point:** The image demonstrates classic signs of **acute paronychia**, characterized by acute inflammation and infection of the periungual tissues. Acute paronychia is an acute infection of the nail fold, most commonly caused by *Staphylococcus aureus*. It typically presents with rapid onset of pain, redness, and swelling around the nail, often with pus formation. The infection usually results from minor trauma to the nail fold, such as nail biting, aggressive manicuring, or hangnail pulling, which allows bacteria to enter. ## Differential Diagnosis | Feature | Acute Paronychia | Herpetic Whitlow | Felon | Onychomycosis | | :------------------ | :--------------------------------------------- | :--------------------------------------------------- | :------------------------------------------------ | :--------------------------------------------- | | **Appearance** | Erythema, swelling, pus at nail fold | Vesicles/bullae (often grouped), erythema, pain | Deep-seated, throbbing pain, swelling of fingertip pulp | Nail discoloration, thickening, subungual debris | | **Location** | Periungual (nail fold) | Often periungual, but can be anywhere on finger | Distal fingertip pulp | Nail plate and bed | | **Pathogen** | *Staphylococcus aureus* (most common) | Herpes Simplex Virus (HSV) | *Staphylococcus aureus* (deep space infection) | Dermatophytes (fungi) | | **Key Distinguisher** | Pus at nail fold, bacterial infection | Vesicles, often history of oral herpes | Entire fingertip pulp involved, severe throbbing pain | Chronic, nail changes, no acute inflammation | ## Clinical Relevance **Clinical Pearl:** Early recognition and treatment of acute paronychia are crucial to prevent progression to more severe infections like felon or osteomyelitis. Incision and drainage are often required for collections of pus. ## High-Yield for NEET PG **High-Yield:** *Staphylococcus aureus* is the most common causative organism for acute paronychia. **Key Point:** Acute paronychia typically results from minor trauma to the nail fold, creating an entry point for bacteria. ## Common Traps **Warning:** Differentiating acute paronychia from herpetic whitlow is important, as incision and drainage is contraindicated in herpetic whitlow due to the risk of secondary bacterial infection and viral dissemination. Look for vesicles in herpetic whitlow. ## Reference [cite:Harrison's Principles of Internal Medicine, Ch 133; Robbins Basic Pathology, Ch 25]