DISCUSSION
Photosensitivity to hydrochlorothiazide was the obvious culprit, so the patient was advised to stop using that product (after consulting his PCP). He’ll remain off the medication for at least two months, then present for follow-up.
There are some potentially troubling items in the differential, particularly dermatomyositis (DM). Patients with DM may exhibit a sunburn-like rash, but they will additionally demonstrate muscle weakness and chronic fatigue. A significant proportion of their complaints are driven by an occult carcinoma (eg, stomach, lung, colon, breast). While it’s doubtful that this patient has DM, his follow-up may include a fresh biopsy, blood work, anteroposterior and lateral chest films, and possibly a colonoscopy.
Another item in the differential is lupus. However, the original biopsy yielded no suggestive findings (eg, interface dermatitis), nor did the patient have any complaints referable to the disease.
This case nicely demonstrates the concept that it is equally important to note which areas are affected by and spared by a skin condition. With that in mind, we can at least establish that sunlight is a major factor in the genesis of this rash. Unfortunately, that still leaves room for conjecture as to the diagnosis.
TAKE-HOME LEARNING POINTS
- Rashes confined to sun-exposed skin can be a symptom of systemic disease, such as lupus or dermatomyositis.
- Various drugs—including hydrochlorothiazide, NSAIDs, sulfas, and certain tetracyclines—can also cause photosensitivity reactions.
- Hydrochlorothiazide is one of the more common drugs to cause such a rash, which may take weeks to clear after cessation of use.
- If terminating hydrochlorothiazide doesn’t help, skin biopsy and labs (especially creatine kinase and immunoglobulins) are the next step in determining the problem.