Here are some diagnoses which “fall between the cracks” – not truly dermatological, but often referred to dermatology.
Notalgia Paraesthetica: intense itch localised to medial border of scapula. It may tingle or burn, often continuous. There may be a 2ndary change in the skin and thinning of the shirt (!) from scratching. Due to a “pinched nerve”
Brachio-Radial summer Prurigo: unilateral or bilateral, upper forearms. Damaged nerves demonstrable during the summer which recovers out of season.
Ano-genital itch: rule out fungus, yeast etc. You should ask:
“Do you have any other sensations?” they usually have - burning, itching, crawling etc which point to a neuritis rather than a dermatitis. Creams can make things worse as their oil -water mix is unstable and requires an added stabiliser (e.g. propylene glycol or other alcohol) which burn, and can cause a contact dermatitis.
Causalgia Paraesthetica: tingling/numbness/altered sensation. Due to pressure on the lateral cutaneous nerve of thigh which sometimes runs through the inguinal ligament. Also known as meralgia paraesthetica. Pregnancy and external pressure can be causes.
For all of these you can try: amitriptyline, nortriptyline, gabapentin, doxepine, carbemazepine or trazodone.
Capsaicin/capsicum: depletes substance P. Treat for 2 – 3 weeks, though it is usually worse until the substance P is depleted and can be quite unbearable during this time.
Para vertebral injections of triamcinolone an option.
Antihistamines have no anti-pruritic effects unless the patient has a histamine-related problem (urticaria); otherwise they only help by their sedative action (i.e. if non-sedative, they don’t help!) Sedative antihistamines impair driving performance, with no patient insight! Most pilots are not allowed to use antihistamines within 24 hours of flying.
Steroids are anti-inflammatory: they work well for atopic dermatitis, but not for the above conditions. The dangers of steroids are over-rated: when used correctly they are very safe. Even if the patient gets thinning of the sin, this is temporary.
Study from England showed great fear of steroid creams and 25% did not even fill their prescriptions. Compliance is therefore very poor. In a study with a microchip-cap (which records how often the cap is removed) poor compliance (55%) was evident - in spite of patient reports of reliable usage. Steroidophobia is a real problem!
Cradle Cap in Old Ladies. Some old ladies have their hair washed professionally and “done” once a week and don’t wash their hair in between. If they have a tendency to seborrhoea dermatitis (dandruff) there can be a huge build up of keratin equivalent to cradle cap in babies. They are reluctant to shampoo out the seborrhoea which would be the logical treatment; these patients often present with itching scalp. What can we advise?
I (JRT) use a liquid topical steroid and they put this on every day for several days and this stops the itching. End up using it once or twice per week. Difficult to apply; part the hair and apply it every 1 inch along the part. Then part the hair 1 inch over and repeat until the whole scalp is covered. But the steroid won’t penetrate the thick keratin layer if they have full-blown cradle cap. For this they need a 25% urea lotion. Often you find this under the foot-care section at the chemist (drug-store). Put it on, rub it in, and wear a shower cap overnight on the night before they have their hairdo! The hairdresser can wash it out along with the keratin next day.
Nail Lifting (onychomycosis). The attachment of the nail to its bed is weaker with age and weakened by moisture. The longer the nail, the greater the leverage to loosen the nail.
The “gap” can be colonised by yeast and bacteria. Infection/colonisation can occur likewise under the cuticle due to repeat water exposure - chronic paronychia. Hairdressers, bar-tenders, nurses, doctors and new-mothers are especially vulnerable. Decrease water exposure. Miconazole liquid under the cuticle or the nail. Do it for 3 months until the new cuticle grows.
Note also acute paronychia (a “felon”)
Exostosis under the nail – hard lump. X-Rays confirm. Refer to orthopaedics if they want it fixed.
Mucus Cyst: trench in the nail. Sometimes a bulge at the base of the nail. This sometimes communicates with the dip joint. Contain clear gelatinous fluid. More common on fingers than toes. Repeated drainage using a needle (issue patient with sterile needles!) Surgery/electrocautery etc
Peri-ungual fibromas (pink sausage-like) of tuberous sclerosis. Also they have adenoma sebaceum (pink-yellow peri-nasal papules which develop at puberty) on face, Ash-Leaf patches (oval, white, patches) Shagreen patch (yellowish, ‘cobblestone’ lumpy plaques at base of spine)
and confetti-like de-pigmentation on arms and legs.
A dominantly inherited geno-dermatosis. Fibromas can occur in the brain (possible seizures), kidney, lung etc
Other features: retinal changes (50%), hyperplastic gums, phacomas, gliomas, pigmentation of basal ganglia etc- i.e. a systemic disease well worth diagnosing!
Abstract by BAS.