1. This is the only skin lesion on this patient. The lesion always recurs in exactly the same place after ingestion of a particular drug. Which drug is most commonly implicated in this type of reaction?
b) Trimethoprim-sulfamethoxazole
A sharply demarcated erythematous, oval, or circular macule is the characteristic lesion of a fixed drug eruption. Usually there is only one lesion, but two or more may be present. Usually the lesions do not itch, but sensations of heat and burning are common. There are no systemic symptoms. As the name implies, the lesions always recur in exactly the same place, although they may vary in size. Healing takes place with pigmentation; if recurrences occur, the affected areas become more pigmented until, finally, dark pigmented patches remain between attacks. The fixed eruption is the only eruption for which drugs or food chemicals are implicated as the sole etiological agent. Cross-reactions to both related and totally different types of drugs have been found. If skin is transplanted from a previously affected area to any other location, it retains for a short time its reactive power. Later, it loses its sensitivity to the particular drug. Conversely, normal skin transplanted into the affected area may become sensitized. Drugs reported to cause a fixed drug reaction include sulfonamides, tetracycline, nonsteroidal anti-inflammatory drugs, barbiturates, and carbamazepine among others (ie, drugs, foods, chemicals).
References
Monroe JR. Lesions that continue to recur in the same place. Fixed drug eruption (FDE). JAAPA. 2012;25(2):21. doi:10.1097/01720610-201202000-00003
Pérez-Ezquerra PR, Sanchez-Morillas L, Alvarez AS, Gómez-Tembleque MP, Moratiel HB, Martinez JJ. Fixed drug eruption caused by amoxicillin-clavulanic acid. Contact Dermatitis. 2010;63(5):294-296. doi:10.1111/j.1600-0536.2010.01802.x
Walling HW, Swick BL. Cutaneous fixed drug eruption to fluconazole. J Drugs Dermatol. 2010;9(8):1025-1028.
2. Which test below would be most helpful to establish the correct diagnosis of half and half nails?
a) Renal function tests
Fifty percent of patients with half and half nails have chronic renal disease. Thus, the correct answer is renal function tests should be done. The other choices are not likely to be helpful. n
References
Iorizzo M, Daniel CR, Tosti A. Half and half nails: a past and present snapshot. Cutis. 2011;88(3):138-139.
James WD, Berger TG, Elston DM. Andrews’ Diseases of the Skin: Clinical Dermatology. 10th ed. Philadelphia, PA: WB Saunders; 2005.
Dr McMichael is professor and chair in the department of dermatology at Wake Forest Hospital Health in Winston-Salem, NC.
