Though the field of dermatology is ‘vely vely scaly’ to many family doctors, over 30% of primary care visits involve a skin complaint (1). And, “Skin Disorder” is one of the 99 topics you’re expected to know for the Family Medicine exam. It’s possible that it might show up on a SOO, but it is completely fair game for a SAMP, and will commonly be encountered in your practice.
Most of us are very familiar with eczema, or atopic dermatitis. Many FP’s see babies at well-baby visits (at 2, 4, 6 months etc.) presenting with an “itchy rash” on their cheeks, belly and dorsal hands. Likewise, we’ve seen kids and some adults with dry, chronically itchy skin on their flexor surfaces (e.g. elbow creases and the backs of knees), who may also have associated atopic conditions, such as allergic rhinitis (hay fever) and asthma.
Treatment usually consists of emollients and topical steroids. A great reference is the Canadian Practical Guide for the Treatment and Management of Atopic Dermatitis (2).
But what if we treat eczema with steroid creams, and not only does it fail to respond, but it gets worse?
SNAP SAMP (BONUS -- See the Practice Pearl Below!):
A 40-year-old female has had an itchy, scaly left foot for over a year, and has been applying betamethasone valerate 0.05% cream BID for 4 weeks now, as prescribed to her by thefirst-year family medicine resident. She returns to clinic with worsening of her rash,asking you, the new staff physician, for a stronger steroid to “clear the eczema”. Whenyou look at her foot, you notice erythematous faint papules on the plantar side of her footwith lots of scaling. You also see that she has thickened yellow nails covered with blacknail polish (hiding the evidence!).
What is the correct diagnosis?
Where else would you look to confirm your hypothesis?
How would you treat it?
What is her toenail condition called, and what investigations would you order?
Tinea Pedis (a fungal infection)
Between her toes, especially 4th and 5th digits (look for interdigital scaling typicalof tinea pedis).
Stop all topical steroids. Prescribe either topical or oral antifungal agents, such asTerbinafine.
Onychomycosis (or Tinea Ungum). Toe nail clippings sent for Fungal Culture(ensure to get all the ‘dirt’ under the nails, as that’s where the fungus lives) arecommonly sent however, direct microscopy of a Potassium Hydroxide preparationis usually adequate.
PRACTICE PEARL: There is a high false-negative rate for nail clippings so sending two samples may be necessary to confirm the absence of fungus. (3)
Lowell, BA et al. Dermatology in primary care: Prevalence and patientdisposition. J Am Acad Dermatol. 2001 Aug;45(2):250-5. Available from: https://www.ncbi.nlm.nih.gov/pubmed/1146418
Lynde, Charles et al. Canadian Practical Guide for the Treatment andManagement of Atopic Dermatitis. Journal of Cutaneous Medicine and SurgeryIncorporating Medical and Surgical Dermatology. 2005 Jun. Available from: https://www.researchgate.net/publication/38013276_Canadian_Practical_Guide_for_the_Treatment_and_Management_of_Atopic_Dermatitis
Gupta A et al. Diagnosing onychomycosis. Clinics in Dermatology (2013) 31, 540–543
Image by Kibbledoode1411 at the English language Wikipedia, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=6672931