Purpuric rash in an infant after chicken pox exposure.

A 7 month-old boy presented with a 1-day history of periauricular and lower limb swelling plus rash.

He had been refusing to weight bear and had a temperature.

Numerous macules were noted over the limbs, face, but his trunk was spared. The lesions were 1–2 cm well-circumscribed purpura, which varied from red to brown (Fig. 1). His lower limbs showed signs of oedema. He was systemically well.

Figure 1

Well-circumscribed oval and round purpuric lesions over the upper and lower limbs.

As this child had been exposed to chickenpox, a differential diagnosis of haemorrhagic varicella and septicaemia were considered. Blood results showed a mildly raised WCC and a C-reactive protein (CRP) of 68. He was diagnosed with acute haemorrhagic oedema of infancy (AHOI) and treated symptomatically. In the following week, he developed a vesicular rash and was diagnosed with chicken pox (Fig. 2).

Figure 2

Small papules and vesicles over the scalp, face, trunk and limbs characteristic of varicella.

AHOI is a rare small vessel vasculitis characterized by large purpuric lesions, fever and oedema. It can occur in children between 4 months and 2 years with a recent upper respiratory tract infection [1]. It may be triggered by viral infections, medication and immunizations. This case demonstrated AHOI secondary to varicella zoster.

The AHOI rash has non-tender, annular and purpuric lesions, with associated non-pitting oedema, which has been reported to be tender [1, 2]. It typically spares the trunk, affecting the face, ears and limbs. Individual lesions can increase in size and coalesce as the disease progresses. It has been noted by Fiore et al that WCC and CRP can be slightly elevated as with our patient [1].

AHOI can be misdiagnosed as haemorrhagic varicella or septicaemia but there is no indication for antibiotic cover if there is no other source of sepsis suspected. [1] The management is symptomatic, with resolution taking an average of 2 weeks [3].

Learning points

AHOI is a benign vasculitis characterized by a triad of fever, oedema and purpuric rash.

Common triggers include preceding viral infection, medication (penicillin and cephalosporin’s) and immunisations. This case demonstrated AHOI likely secondary to varicella zoster as have other reported cases [4, 5].

Only symptomatic treatment is indicated.