Spot the Rash

A 14-year-old female presents with a rash on the trunk for 2 weeks

Marissa J. Perman
Figure 1. Abdomen with several scattered pink, scaly, round and oval papules and thin plaques.

Source: Marissa J. Perman, MD

A 14-year-old female presents to your clinic with a rash for 2 weeks. Initially, the rash began as a single oval scaly patch on the chest that was concerning for ringworm. The patient tried over-the-counter antifungal cream twice daily without improvement. The following week, she developed several more similar looking but smaller lesions on her abdomen and back. The rash is mildly pruritic. Her mother is very concerned it is contagious. On exam, the patient appears well. You see many round and oval pink, peripherally scaling patches and thin plaques on the chest, abdomen, back, inguinal folds and axillae.

Can you spot the rash?

A. Tinea corporis

B. Pityriasis rosea

C. Atopic dermatitis

D. Nummular dermatitis

E. Secondary syphilis

Case Discussion

The answer is B, pityriasis rosea (PR), a common, reactive eruption thought to be due to a virus, which is seen more in the spring and fall. It may be seen in patients of all ages but is more common in children. PR begins as a single lesion, usually on the trunk, often larger than the subsequent lesions that develop and is referred to as the “herald patch” (Figure 1). Within several days to weeks, patients develop many more lesions that tend to follow skin tension lines or a “Christmas tree pattern,” particularly on the back. Lesions can often be found in flexural surfaces such as the axillae and inguinal folds. The rash tends to spare the face and lower body. PR lasts on average about 6 to 8 weeks, then self-resolves but occasionally can last as long as 12 weeks. Symptoms may range from asymptomatic to severely pruritic.

Because the “herald patch” is often round and scaly, it is often mistaken for tinea corporis (TC) until the remainder of the eruption appears. Classically, TC is annular (clears in the middle), whereas PR is not. PR can also be confused with atopic dermatitis (AD), particularly the nummular subtype, which presents as pruritic, erythematous, scaling thin plaques on the trunk and extremities. A history of atopy in the patient or family may help to distinguish these disorders, and AD often responds well to topical corticosteroids. Other considerations in the differential diagnosis include secondary syphilis, which can also appear as multiple, pink, round and oval scaling papules and thin plaques concentrated on the trunk. Palm and sole involvement is often a clue for syphilis, which is uncommonly seen in PR. Obtaining a sexual history is important, especially in teenagers. When in doubt, checking a rapid plasma reagin (RPR) is very reasonable.

Treatment is mainly supportive because PR is benign and runs a relatively uncomplicated course for most patients. Due to its prolonged nature in some patients (up to 12 weeks), reassurance is key. For pruritus, mildly potent topical steroids can be prescribed to help with itch, but they do not facilitate resolution. Phototherapy and natural sunlight have been shown to be helpful in some patients. Additionally, there is some evidence for using antiviral medications, such as acyclovir, for a short period early in the course.

Patient history can be key when trying to differentiate PR from other similar eruptions, particularly when patients report a “herald patch.” PR should be distinguished from similar rashes, especially secondary syphilis, either clinically or by serology. Providers should consider PR in the differential diagnosis of a new-onset, truncal, mildly pruritic, scaling pink eruption, especially in the fall and spring, in their pediatric patients.

Disclosure: Perman reports no relevant financial disclosures.

Marissa J. Perman
Figure 1. Abdomen with several scattered pink, scaly, round and oval papules and thin plaques.

Source: Marissa J. Perman, MD

A 14-year-old female presents to your clinic with a rash for 2 weeks. Initially, the rash began as a single oval scaly patch on the chest that was concerning for ringworm. The patient tried over-the-counter antifungal cream twice daily without improvement. The following week, she developed several more similar looking but smaller lesions on her abdomen and back. The rash is mildly pruritic. Her mother is very concerned it is contagious. On exam, the patient appears well. You see many round and oval pink, peripherally scaling patches and thin plaques on the chest, abdomen, back, inguinal folds and axillae.

Can you spot the rash?

A. Tinea corporis

B. Pityriasis rosea

C. Atopic dermatitis

D. Nummular dermatitis

E. Secondary syphilis

PAGE BREAK

Case Discussion

The answer is B, pityriasis rosea (PR), a common, reactive eruption thought to be due to a virus, which is seen more in the spring and fall. It may be seen in patients of all ages but is more common in children. PR begins as a single lesion, usually on the trunk, often larger than the subsequent lesions that develop and is referred to as the “herald patch” (Figure 1). Within several days to weeks, patients develop many more lesions that tend to follow skin tension lines or a “Christmas tree pattern,” particularly on the back. Lesions can often be found in flexural surfaces such as the axillae and inguinal folds. The rash tends to spare the face and lower body. PR lasts on average about 6 to 8 weeks, then self-resolves but occasionally can last as long as 12 weeks. Symptoms may range from asymptomatic to severely pruritic.

Because the “herald patch” is often round and scaly, it is often mistaken for tinea corporis (TC) until the remainder of the eruption appears. Classically, TC is annular (clears in the middle), whereas PR is not. PR can also be confused with atopic dermatitis (AD), particularly the nummular subtype, which presents as pruritic, erythematous, scaling thin plaques on the trunk and extremities. A history of atopy in the patient or family may help to distinguish these disorders, and AD often responds well to topical corticosteroids. Other considerations in the differential diagnosis include secondary syphilis, which can also appear as multiple, pink, round and oval scaling papules and thin plaques concentrated on the trunk. Palm and sole involvement is often a clue for syphilis, which is uncommonly seen in PR. Obtaining a sexual history is important, especially in teenagers. When in doubt, checking a rapid plasma reagin (RPR) is very reasonable.

Treatment is mainly supportive because PR is benign and runs a relatively uncomplicated course for most patients. Due to its prolonged nature in some patients (up to 12 weeks), reassurance is key. For pruritus, mildly potent topical steroids can be prescribed to help with itch, but they do not facilitate resolution. Phototherapy and natural sunlight have been shown to be helpful in some patients. Additionally, there is some evidence for using antiviral medications, such as acyclovir, for a short period early in the course.

Patient history can be key when trying to differentiate PR from other similar eruptions, particularly when patients report a “herald patch.” PR should be distinguished from similar rashes, especially secondary syphilis, either clinically or by serology. Providers should consider PR in the differential diagnosis of a new-onset, truncal, mildly pruritic, scaling pink eruption, especially in the fall and spring, in their pediatric patients.

Disclosure: Perman reports no relevant financial disclosures.