Spot the Rash

A 6-year-old male with rash on the legs

A 6-year-old male presented to a dermatology clinic with a 1-week history of rash on his lower legs. His parents reported the rash started on the buttocks and then spread to the lower legs. It was mildly pruritic, and he had been prescribed a topical antibiotic for some of the open areas.

Aditi Murthy
Marissa J. Perman

He was generally feeling well but complained of abdominal pain the previous night.

Patient presented a 1-week history of rash on his lower legs, which was reported to have started on the buttocks and then spread to the lower legs.

Source: Aditi Murthy, MD

On examination, the patient was generally well appearing. On the buttocks and lower extremities, there were palpable purpuric papules and thin plaques without overlying scale. There was no scrotal edema.

Can you spot the rash?

A. Acute meningococcemia

B. Urticaria

C. Henoch-Schönlein purpura

D. Contact dermatitis

E. Insect bites

Case Discussion

Henoch-Schönlein purpura (HSP) usually begins with a few days of prodromal symptoms, followed by development of a rash. The etiology is likely a combination of infectious trigger and genetic predisposition, with the most common infectious triggers being viruses and group A streptococcal infection. HSP is the most common vasculitis of childhood.

The rash of HSP consists of nonblanching, red-purple macules and papules that tend to favor the lower half of the body. Lesions can be itchy or, less commonly, painful. Other symptoms that can accompany the rash and suggest extracutaneous involvement include joint pain and swelling, abdominal pain and blood in stool or urine. Basic laboratory workup including a urinalysis is mandatory. Skin biopsy is not always performed in children for diagnosis but would show a small vessel vasculitis. If a biopsy is performed, direct immunofluorescence studies show prominent IgA deposition is helpful in differentiating HSP from different types of small vessel vasculitides. Patients may be treated with supportive care only or, in some cases, may require oral steroids.

Acute disseminated meningococcal infection can present with widespread purpuric lesions. A typical case scenario for that condition would be a systemically unwell child with a high fever, headache and/or neck stiffness who develops a progressive petechial and purpuric eruption. Patients require emergent antibiotics because this condition is life-threatening.

Urticaria can present as widely distributed papules and plaques. Compared with the lesions found on this patient, urticarial lesions are typically lighter pink in color, edematous and transient. Single lesions of classic urticaria usually last less than 24 hours in most cases. Unlike vasculitis, acute urticaria usually responds to systemic antihistamines.

This eruption would be a very unusual distribution for contact dermatitis. Purpuric contact dermatitis would be expected to present with a geometric plaque at the exposed site. Of note, there are variants of contact dermatitis that appear more purpuric, such as an allergy to the hair dye component paraphenylenediamine.

Finally, insect bites could be considered in the differential diagnosis. The primary lesions are usually pruritic and tend to favor exposed areas of skin, such as the distal lower extremities. The wide distribution and the red-purple color of the lesions, as well as the systemic symptoms, do not support this diagnosis for this patient.

HSP should be highly considered in a young child with acute onset of purpuric lesions.

Disclosure: Murthy and Perman report no relevant financial disclosures.

A 6-year-old male presented to a dermatology clinic with a 1-week history of rash on his lower legs. His parents reported the rash started on the buttocks and then spread to the lower legs. It was mildly pruritic, and he had been prescribed a topical antibiotic for some of the open areas.

Aditi Murthy
Marissa J. Perman

He was generally feeling well but complained of abdominal pain the previous night.

Patient presented a 1-week history of rash on his lower legs, which was reported to have started on the buttocks and then spread to the lower legs.

Source: Aditi Murthy, MD

On examination, the patient was generally well appearing. On the buttocks and lower extremities, there were palpable purpuric papules and thin plaques without overlying scale. There was no scrotal edema.

Can you spot the rash?

A. Acute meningococcemia

B. Urticaria

C. Henoch-Schönlein purpura

D. Contact dermatitis

E. Insect bites

PAGE BREAK

Case Discussion

Henoch-Schönlein purpura (HSP) usually begins with a few days of prodromal symptoms, followed by development of a rash. The etiology is likely a combination of infectious trigger and genetic predisposition, with the most common infectious triggers being viruses and group A streptococcal infection. HSP is the most common vasculitis of childhood.

The rash of HSP consists of nonblanching, red-purple macules and papules that tend to favor the lower half of the body. Lesions can be itchy or, less commonly, painful. Other symptoms that can accompany the rash and suggest extracutaneous involvement include joint pain and swelling, abdominal pain and blood in stool or urine. Basic laboratory workup including a urinalysis is mandatory. Skin biopsy is not always performed in children for diagnosis but would show a small vessel vasculitis. If a biopsy is performed, direct immunofluorescence studies show prominent IgA deposition is helpful in differentiating HSP from different types of small vessel vasculitides. Patients may be treated with supportive care only or, in some cases, may require oral steroids.

Acute disseminated meningococcal infection can present with widespread purpuric lesions. A typical case scenario for that condition would be a systemically unwell child with a high fever, headache and/or neck stiffness who develops a progressive petechial and purpuric eruption. Patients require emergent antibiotics because this condition is life-threatening.

Urticaria can present as widely distributed papules and plaques. Compared with the lesions found on this patient, urticarial lesions are typically lighter pink in color, edematous and transient. Single lesions of classic urticaria usually last less than 24 hours in most cases. Unlike vasculitis, acute urticaria usually responds to systemic antihistamines.

This eruption would be a very unusual distribution for contact dermatitis. Purpuric contact dermatitis would be expected to present with a geometric plaque at the exposed site. Of note, there are variants of contact dermatitis that appear more purpuric, such as an allergy to the hair dye component paraphenylenediamine.

Finally, insect bites could be considered in the differential diagnosis. The primary lesions are usually pruritic and tend to favor exposed areas of skin, such as the distal lower extremities. The wide distribution and the red-purple color of the lesions, as well as the systemic symptoms, do not support this diagnosis for this patient.

HSP should be highly considered in a young child with acute onset of purpuric lesions.

Disclosure: Murthy and Perman report no relevant financial disclosures.