SU18.1 | Cutaneous and Subcutaneous Infections — Summary & Reflection

KEY TAKEAWAYS

Cutaneous and subcutaneous infections span a spectrum, and the whole skill is deciding where a patient sits on it. They are classified by depth and by whether they form localised pus (suppurative) or spread diffusely (non-suppurative). Staphylococcus aureus causes the follicular, pus-forming group — folliculitis → furuncle (boil) → carbuncle (diabetics, nape of neck) — and abscesses; Streptococcus pyogenes causes spreading cellulitis and superficial erysipelas. The decisive bedside sign is fluctuance: present = pus = incision and drainage (ubi pus, ibi evacua); absent = cellulitis = antibiotics and elevation. A carbuncle needs drainage/excision plus antibiotics and diabetic control. Necrotizing fasciitis — pain out of proportion, dusky/blistering skin, crepitus, a toxic patient — is a surgical emergency whose only definitive treatment is immediate radical debridement alongside resuscitation and broad-spectrum antibiotics; hesitation is the fatal error.

REFLECT

Recall a patient you have seen with a 'skin infection' — a boil, a red leg, a wound that turned nasty — or imagine clerking one in your next emergency shift. Did you deliberately feel for fluctuance to decide whether there was pus to drain, and did you mark and date the edge of any cellulitis so its spread could be judged? Now consider the dangerous end of the spectrum: would you have recognised pain out of proportion, crepitus and a toxic patient as a necrotizing infection, and would you have had the confidence to escalate to theatre rather than start oral antibiotics and wait? Reflect on one habit you will build — checking blood glucose in every boil and carbuncle, or never reassuring on mild-looking skin in a very unwell patient — so that the right decision becomes automatic.