Skin infection, infestation and sexually transmitted disease
Infectious dermatology combines morphology with organism, depth, host defenses, exposure and the consequences of delay. Superficial impetigo, a sharply demarcated erysipelas pattern and deeper cellulitis are related but different presentations. Bullous staphylococcal disease involves toxin-mediated disruption of a specific adhesion protein rather than every cause of blistering. Rapidly progressive pain, systemic illness, necrosis or tissue gas require urgent assessment for a deeper destructive infection; a benign-looking early surface does not establish safety. Microbiological sampling supports the assessment but should be interpreted with the clinical syndrome and urgency.
Dermatophyte infection can affect scalp, body, feet and nails. The site, inflammatory pattern and species can influence treatment. Tinea capitis usually requires systemic therapy rather than topical treatment alone, but a Wood lamp is not a universal rule-out test: fluorescence depends on the organism and examination conditions. KOH examination, culture, histology or molecular methods answer different questions. A negative initial sample can reflect sampling limitations. An annular scaly lesion altered by corticosteroids can be misleading, so treatment history and mycological evaluation can matter.
Viral eruptions and infestations have characteristic clues without being perfectly specific. HSV and VZV can produce multinucleated cells on cytology, which does not independently distinguish the virus or its type. Eczema herpeticum and ophthalmic or neurological zoster features require prompt qualified assessment. In scabies, contact management, correct application and reinfestation assessment matter; persistent itch alone does not prove viable mites after treatment. The actual patient group and medicine-specific restrictions still govern therapy. A single contact-treatment sentence is not a complete prescription for every infant or pregnant patient.
Venereology requires respectful sexual history, appropriate testing and clinical staging. Primary and secondary syphilis can have different presentations, and early serology can be negative. A prozone effect is an analytical issue caused by antibody excess and may be clarified by appropriate dilution. Treponemal positivity can persist after treatment, so it is not identical to active disease or treatment failure. Genital ulcer morphology and discharge guide the differential but do not replace the appropriate lesion or molecular tests. Antimicrobial selection and follow-up depend on the named current guideline, resistance, pregnancy, neurological or ocular involvement and prior treatment. Local notification and confidentiality duties require the actual jurisdiction and cannot be imported from another country's bank.