What causes post-streptococcal pustulosis (post-streptococcal, Group A beta-hemolytic streptococcus)?

From the Guidelines

Poststreptococcal pustulosis is primarily caused by an immune reaction following a streptococcal infection, typically group A Streptococcus, as evidenced by the body's immune response to streptococcal antigens 1. The condition occurs when the body's immune system, after fighting off the streptococcal bacteria, mistakenly attacks healthy skin cells. The immune response is triggered by molecular mimicry, where streptococcal antigens share structural similarities with human skin proteins, causing cross-reactivity. This leads to the formation of sterile pustules, typically appearing 1-3 weeks after the initial streptococcal infection, often on the trunk and extremities. The condition is not directly infectious but results from the body's abnormal immune response. Some key points to consider in the management of poststreptococcal pustulosis include:

• The use of topical corticosteroids like betamethasone 0.1% cream applied twice daily for 7-14 days to reduce inflammation 1.
• For more severe cases, oral antibiotics such as penicillin V 500mg four times daily for 10 days may be prescribed to eliminate any remaining streptococcal bacteria.
• Symptomatic relief can be achieved with antihistamines like cetirizine 10mg daily.
• The condition usually resolves within 2-3 weeks with appropriate treatment, though recurrence is possible with subsequent streptococcal infections. It's worth noting that the most recent and highest quality study 1 recommends managing impetigo, erysipelas, and cellulitis with antibiotics against Gram-positive bacteria, which is relevant to the treatment of poststreptococcal pustulosis. Key considerations in the treatment of poststreptococcal pustulosis include:
• Prompt treatment with agents effective against the typical Gram-positive pathogens, especially streptococci.
• The use of oral beta-lactams, macrolides, and lincosamides as available options, although resistance to erythromycin and clindamycin is increasing.
• The consideration of fluoroquinolones for the treatment of most uncomplicated cellulitis, but not for MRSA infections.
• The use of glycopeptides and newer antimicrobials for more severe infections or when MRSA is suspected.

From the Research

Causes of Poststreptococcal Pustulosis

• Poststreptococcal pustulosis is a condition that occurs after a streptococcal infection, as reported in a case study where a patient developed an acute diffuse pustular eruption after a subcutaneous injection of secukinumab, and streptococcus was isolated from throat swabs 2.
• The condition is characterized by an elevated antistreptolysin titre, and it is distinct from acute generalized exanthematous pustulosis and pustular psoriasis, with a distinct clinical presentation of isolated pustules on normal skin, predominantly in an acral location 3.
• Group A beta-hemolytic streptococcus can cause several postinfectious, nonsuppurative immune-mediated diseases, including poststreptococcal reactive arthritis, which may be related to poststreptococcal pustulosis 4, 5.
• A case study reported a 6-year-old boy with a diffuse acute pustular eruption that appeared after an erysipela, which was diagnosed as pustulosis acuta generalisata, and the patient responded well to antibiotic treatment 6.

Relationship with Streptococcal Infection

• The evidence suggests that poststreptococcal pustulosis is a post-streptococcal disease, and the condition is often associated with an elevated antistreptolysin titre 3.
• The infection with group A beta-hemolytic streptococcus can trigger an immune-mediated response, leading to poststreptococcal pustulosis and other related conditions 4.
• The diagnosis of poststreptococcal pustulosis is often based on the clinical presentation, history of streptococcal infection, and laboratory tests, including antistreptolysin titre 2, 3.