A 28-year-old woman presented to hospital with a 1-week history of diarrhoea (three soft, non-bloody stools daily), 2 days of vomiting, and a 12-hour history of a purpuric truncal rash.

Five years previously, she had experienced a 1-month diarrhoeal illness, managed as an outpatient. At that time, the full blood count and erythrocyte sedimentation rate were within the normal range. Faecal microscopy had shown scanty leukocytes. Colonoscopy was scheduled; however, the symptoms disappeared and investigation did not proceed. The patient subsequently suffered from mild, intermittent diarrhoea. Her uncle had a history of inflammatory bowel disease, although the patient was not aware of this when she first presented to us.

On presentation, her vital signs were normal. There was mild right upper quadrant abdominal tenderness, and multiple large, purpuric lesions over the trunk. Blood tests suggested a systemic inflammatory response and mild disseminated intravascular coagulation (Box 1). Faecal microscopy was positive for leukocytes and erythrocytes.

The differential diagnosis was broad, and included systemic infection (such as meningococcaemia), Henoch Schönlein purpura, the antiphospholipid syndrome, thrombotic thrombocytopenic purpura, and purpura fulminans associated with protein C deficiency.

Ceftriaxone and enoxaparin were commenced as empirical treatment for infection and/or purpura fulminans. Over the next day, the skin lesions became larger and confluent, with new lesions on the legs and perineum. A morphine infusion was required for analgesia. Four units of fresh frozen plasma were infused for suspected protein C deficiency, while awaiting laboratory test results. These confirmed a slightly reduced functional protein C level (63%). This was considered most likely an acquired deficiency, as seen in inflammatory states. Further fresh frozen plasma or protein C replacement was regarded as unnecessary.

Additional tests for prothrombotic (Box 1) and autoimmune diseases (antinuclear, extractable nuclear antigen, and double-stranded DNA antibodies) revealed no abnormality. Thrombocytopenic purpura was excluded by the finding of a normal haptoglobin level. There was no significant bacterial growth from blood, urine or faeces. Ceftriaxone was ceased on Day 3.

Purpura fulminans was confirmed on skin biopsy by the finding of dermal venous and capillary thrombosis, without evidence of vasculitis (Box 2).

There was no further progression in the number or size of the skin lesions. However, on Day 5, the lesions formed bullae and ulcerated (Box 3). Metronidazole and dicloxacillin were added to treat secondary infection of the ulcers. The morphine infusion was ceased on Day 14, and oral oxycodone was substituted. The results of blood tests taken on Day 22 (Box 1) reflected an ongoing intense systemic inflammatory response. At the time of discharge on Day 23, the patient continued to pass three soft stools daily and had multiple ulcers over the trunk and perineum, which required daily nursing care for wound management. The discharge diagnosis was purpura fulminans, possibly precipitated by an enteric infection.

By Day 36 of the illness, the diarrhoea had resolved. However, the patient remained fatigued, and the blood tests (Box 1) indicated persistent systemic inflammation and rising serum liver enzyme concentrations. Abdominal ultrasound was normal. The liver abnormalities were considered secondary to the oxycodone. Over the ensuing weeks, the analgesia was reduced and stopped, the blood parameters normalised, and the patient returned to her normal level of function. The skin lesions had healed by Week 15, but left significant scarring.

Twenty-five weeks following the onset of the illness, the patient re-presented as an outpatient with a 1-week history of diarrhoea (six watery stools daily). There was one mouth ulcer, but no new skin lesions. A faecal specimen showed only erythrocytes. The erythrocyte sedimentation rate, C-reactive protein, and platelets were slightly elevated (Box 1). The symptoms and abnormal blood parameters resolved completely over the following week. Referral was made for colonoscopy to investigate for inflammatory bowel disease.

The patient presented again, 46 weeks after her original hospitalisation, with a 1-week history of bloody diarrhoea and colicky abdominal pain. The colonoscopy was due the following week. Her vital signs were normal. She had left lower quadrant tenderness. Laboratory tests indicated inflammation and mild coagulation abnormalities (Box 1). She was admitted to hospital. Over the next 24 hours, a purpuric rash consistent with purpura fulminans developed on her abdomen, sacrum and vulva (Box 4). Colonoscopy revealed widespread inflammation involving the entire colon, with multiple deep ulcers, but relative rectal sparing. The histology showed active chronic pancolitis, most suggestive of ulcerative colitis (Box 5). The consensus diagnosis was inflammatory bowel disease (colitis, unspecified). Methylprednisolone 60 mg intravenously was administered daily for 1 week. The skin lesions regressed, without ulceration, and the diarrhoea ceased. She was discharged on a reducing dose of prednisolone. Five months after ceasing prednisolone, she has remained asymptomatic.