Understanding Rash Diagnosis and Treatment: A Case of Pityriasis Rosea vs. Drug Eruption

Written by Dr. Caroline Vaughn

At Village Dermatology, we often see patients with sudden-onset rashes that can be confusing, uncomfortable, and distressing. One such recent case involved a 43-year-old male from the Katy and Memorial Houston area who came in with a red, bumpy, and itchy rash primarily on his left upper arm and trunk.

Patient Background and Symptoms
The patient reported that the rash began five days prior as a single lesion before spreading across his torso and arm. He described it as itchy and irritating but had only tried oral Benadryl with no significant relief. He also noted a recent sinus infection for which he had been prescribed amoxicillin.

Clinical Evaluation and Diagnosis
Upon thorough physical examination using a dermatoscope, the rash presented as well-distributed, erythematous papules on the upper back, epigastric area, and left arm. Based on the clinical presentation and patient history, the differential diagnosis included:

• Pityriasis Rosea – an inflammatory skin condition often preceded by a “herald patch,” common in younger individuals and typically self-limited.

• Drug Eruption – a potential reaction to recent antibiotic use, in this case, amoxicillin.

• Unspecified Dermatitis – a broad classification pending more definitive diagnosis.

Treatment Plan
The patient was prescribed topical triamcinolone 0.1% cream to be applied twice daily for up to two weeks. He was also advised to use antihistamines and soothing lotions like Sarna for itch relief.

Patient Counseling
We discussed the expected course of pityriasis rosea, including its self-limiting nature. The patient was educated on the risks of prolonged steroid use and instructed to avoid applying high-potency creams to sensitive areas like the face or groin.

Follow-Up
A follow-up visit is scheduled in three weeks to reassess the rash’s progression and determine if further intervention is needed.

If you’re experiencing a new rash or skin irritation, don’t wait—schedule an appointment with our board-certified dermatologists today.