Dermclinic: A Photo Quiz to Hone Dermatologic Skills (April 2005)

Case 1: A 39-year-old woman has a tender vesicular rash on her finger. A similar rash that had appeared on the same finger 1 year earlier responded slowly to a course of oral cephalexin. What do you suspect—and how will you rule out the other conditions in the differential? A. Staphylococcus aureus infection. B. Methicillin-resistant S aureus infection. C. Streptococcal infection. D. Herpetic whitlow. E. Candidiasis. Answer on next page , Case 1 Answer: The presence of vesicles on the patient’s hand suggested herpes simplex virus (HSV) infection. Cultures of the lesion grew HSV type 1, which confirmed the diagnosis of herpetic whitlow, D. This condition was common in dental workers and other health care professionals before the use of gloves became universal. HSV infections resolve in about a week, with or without treatment. Antiviral agents, such as famciclovir or valacyclovir, may speed resolution. Streptococcal and staphylococcal infections are not uncommon and must be ruled out. Although the history may be suggestive, the definitive diagnosis can be established only by culture. Candidal infection is unlikely in the absence of an underlying predisposing condition, such as diabetes.    Case 2 on next page , Case 2: For 3 days, a 46-year-old woman has had a slightly tender vesicular rash on her right breast. She has never had a similar rash at this site before, and she denies recent exposure to possible contactants. She is concerned because the rash erupted while her husband was out of town, and he is due to return soon. They have been married for 15 years. To what do you attribute the patient’s rash? A.  Bacterial folliculitis. B.  Candidal folliculitis. C.  Herpes simplex virus infection. D.  Contact dermatitis. E.  Factitial dermatitis. Answer on next page , Case 2 Answer: Viral culture of a lesion grew herpes simplex virus type 1, C.  Further questioning revealed that the patient’s husband had a history of herpes labialis but had not been symptomatic at the last contact before he left town. Herpes simplex has a yearly conversion rate of about 10% between partners in a monogamous relationship; there is a 1-week incubation period. The location and appearance of this patient’s rash would be unusual for bacterial or candidal folliculitis in the absence of trauma or injury. Contact dermatitis is unlikely in this location without a supporting history. Factitial dermatitis does not produce a vesicular eruption.   Case 3 on next page , Case 3: A 67-year-old woman presents with a 3-week history of a tender, pruritic, slowly enlarging eruption between the breasts. The patient has tried overthe- counter hydrocortisone cream, to no avail. She is otherwise healthy. What type of rash is this? A.  Candidiasis. B.  Erythrasma. C.  Dermatophyte infection. D.  Streptococcal infection. E.  Intertrigo. Answer on next page , Case 3 Answer: A potassium hydroxide (KOH) evaluation revealed candidiasis, A. Candida albicans  thrives in moist intertriginous regions. Topical antifungal agents are effective, and the addition of a powder that contains talc or aluminum chloride to keep the area dry will prevent recurrence. The KOH evaluation ruled out dermatophyte and streptococcal infection. (The last entity could also be ruled out with a bacterial culture.) Failure to respond to topical antibiotics would rule out erythrasma. Intertrigo is a diagnosis of exclusion.   Case 4 on next page , Case 4: For several months, a 39-year-old woman has had a slightly tender inflammation of the skin around 1 nail; the nail is ridged. She tried soaking her hand in bleach, which brought no relief.  What is the most likely cause of the woman’s symptoms? A.  Streptococcal infection. B.  Staphylococcal infection. C.  Candidiasis. D.  Contact dermatitis. E.  Dermatophyte infection. Answer on next page , Case 4 Answer: Chronic paronychial infections are considered candidiasis, C, until proved otherwise. The inflammation that resulted from the patient’s infection affected the growing nail plate and produced ridges. Because this is a closed-space infection, oral therapy with ketoconazole or fluconazole is usually necessary. Acute bacterial infections always present with pain. Contact dermatitis is unlikely, because the patient’s condition affected only 1 nail. Dermatophytes do not cause paronychial infection.