A 25-year-old man spent several days on a climbing trip during which one night was spent sleeping on a rock wall. The climber experienced significant abrasions to his hands, as well as numerous tears of the skin on his fingers. Two days after completing the trip the climber noticed increasing pain in the lateral aspect of his right thumb. The climber soaked the thumb in warm saltwater, but over the course of several days the reddening and swelling increased. By the sixth day after returning from the climb, the climber reported that he was able to express pus from the area. Similar areas of redness also developed on the cuticles of his left thumb (Figure). He reported applying topical triple antibiotic ointment (bacitracin, neomycin, polymyxin B) at that time with no improvement. The climber finally presented to an urgent care facility 10 days after the redness first appeared.
The climber's thumbs 8 days after injury.
What is the diagnosis? What is the clinical course? What is the pathophysiology? What is the treatment?
Diagnosis
Bilateral paronychiae due to Streptococcus pyogenes
Clinical course
At presentation there was significant erythema and superficial skin necrosis on the patient's thumbs bilaterally. Copious purulent material was expressed from both of the wounds. The patient was afebrile. After local anesthesia was administered, bilateral incision and drainage of the cuticle regions was performed. Bacterial cultures were taken and Gram stain performed. The patient was started on co-trimoxazole (2 double-strength tablets daily for 7 days) due to concern about community-acquired methicillin-resistant Staphylococcus aureus (CA-MRSA) and instructed to return in 48 hours. The patient was also instructed to apply topical bacitracin. Culture results showed 3+ group A β-hemolytic Streptococcus pyogenes. Upon returning the patient remained afebrile and antibiotic coverage was changed to penicillin 500 mg orally 4 times daily for 10 days to treat S. pyogenes. The patient continued to heal and returned to climbing 3 weeks later.
Background
The patient in this case developed bilateral paronychiae with S. pyogenes after sustaining superficial cuticular injuries while rock climbing. Paronychia is a common malady of the hand in individuals who experience repeated trauma to the cuticle. 1 While acute paronychia is typically unilateral, it can present bilaterally. 2 Even though S. aureus is the most common organism associated with acute paronychia, and CA-MRSA is an increasingly common cause of soft tissue infections presenting to the emergency department, S. pyogenes is also a frequent pathogen and must be considered. 1 ,3,4 Recognition and proper treatment is important because untreated acute paronychia can cause permanent damage to the nail plate and progress to chronic paronychia.2,5
Pathophysiology
Paronychia results from a disruption of the nail cuticle. The cuticle acts as a barrier to the external environment, sealing the space between the nail fold and the distal skin of the digit. 1 When the cuticle is disrupted by trauma, pathogens can enter the lateral nail folds. 1 The most common pathogens (S. aureus and S. pyogenes) reflect common skin fauna; however, if the site has been exposed to nail biting or finger sucking, oral flora can predominate.6,7 One to 2 days after S. pyogenes has gained access to the nail bed the host raises a marked inflammatory response, with neutrophilic infiltration of infected tissue resulting in pus formation. 8 S. pyogenes can express several factors that facilitate its spread through surrounding tissue, such as streptolysins and hyaluronidase or “spreading factor.”9,10S. pyogenes can cause necrotizing fasciitis, scarlet fever, acute glomerulonephritis, and/or streptococcal toxic shock syndrome. 11
Treatment
Treatment of acute paronychia can be divided into surgical and medical therapy. Surgical intervention is indicated if an abscess is suspected. 12 After administration of appropriate local anesthesia, incision and drainage of an abscess can be accomplished with a #11 surgical blade or by tracking a 16- or 18-gauge needle along the nail bed to allow drainage.5,13 Cultures and Gram stain should be obtained and empiric therapy started with agents active against methicillin-sensitive S. aureus (MSSA) and CA-MRSA; cephalexin 500 mg orally 4 times daily for 7 days with co-trimoxazole 2 double-strength tablets orally twice daily for 7 days are recommended, particularly if the incidence of CA-MRSA is high. 3 ,12,14 Antibiotic therapy should then be adjusted pending culture and stain results. If S. pyogenes is cultured, antibiotic therapy with cephalexin, penicillin, or clindamycin should be continued for a total of 10 days.11,15 If an abscess is not present, initial treatment of a paroncyhia consists of warm soaks, with or without topical antibiotics. 1 Empiric oral antibiotics, such as cephalexin with co-trimoxazole should be started if the infection progresses despite warm soaks. 1 ,12,14