Dermatologic System and Eyes, Ears, Nose, and Throat
Core concepts
Skin: learn to separate the common rashes by morphology and distribution. Psoriasis has well-demarcated silvery scale on extensor surfaces; atopic dermatitis is flexural and intensely pruritic; tinea is annular with central clearing; pityriasis rosea follows a herald patch in a Christmas-tree distribution; erythema migrans is the expanding target lesion of early Lyme disease. Screen pigmented lesions with asymmetry, border irregularity, color variation, diameter, and evolution; Breslow depth drives melanoma prognosis.
Drug eruptions matter: Stevens-Johnson syndrome and toxic epidermal necrolysis show mucosal involvement, skin sloughing, and a positive Nikolsky sign; stop the drug and provide burn-level supportive care.
The red eye is a classic discriminator. Bacterial conjunctivitis produces purulent discharge with normal vision; viral conjunctivitis is watery; uveitis causes deep pain, photophobia, ciliary flush, and decreased vision; acute angle-closure glaucoma produces severe pain, halos, a mid-dilated fixed pupil, and a rock-hard globe requiring immediate pressure lowering. Sudden painless monocular vision loss with a pale retina and cherry-red spot is central retinal artery occlusion.
Ears: otitis externa is painful canal inflammation, often pseudomonal, and malignant otitis externa occurs in diabetics. On tuning fork testing, Weber lateralizes to the affected side in conductive loss and to the better ear in sensorineural loss. Peritonsillar abscess shows uvular deviation and trismus and needs drainage.
Traps
- Treating a painful red eye with decreased vision as conjunctivitis.
- Missing ophthalmic zoster, which needs urgent antiviral therapy and eye evaluation.
- Confusing cellulitis with a drainable abscess.
Rule of thumb
Painful red eye with decreased vision and photophobia is uveitis or angle-closure glaucoma, not conjunctivitis; either way, same-day ophthalmology evaluation is required.