Petechiae, purpura and vasculitic rashes — formative SAQs

SAQ 1 (10 marks)

A 14-month-old girl is brought to the emergency department with a six-hour history of fever, irritability and a rash. On examination she is flushed but cool peripherally, with a capillary refill of four seconds, a heart rate of 170 beats per minute and a blood pressure of 78/40 mmHg. A petechial rash over the lower limbs is spreading onto the trunk, with two enlarging dark purpuric patches on the thigh. Her initial full blood count shows a platelet count of 45 × 10⁹ per litre, a prolonged prothrombin time, a low fibrinogen and a markedly raised D-dimer. ^{[8] [9]}

Question: Outline your immediate assessment and triage, the emergency management over the first hour, the interpretation of the blood results, and the disposition and public-health actions. (10 marks) ^[8]

Model answer

Immediate assessment and triage (2 marks). This is a sick child with a rapidly progressive non-blanching rash and signs of septic shock — meningococcal septicaemia with purpura fulminans until proven otherwise. The first split is sick versus well, and this child is unwell: tachycardia, hypotension, prolonged capillary refill and a spreading petechial rash confirm the emergency pathway. Confirm the rash is non-blanching with the glass test, but do not delay treatment to classify it further. ^[8]

Emergency management over the first hour (3 marks). Give high-flow oxygen, establish intravenous or intraosseous access, take blood cultures and a full blood count, film, coagulation, lactate and blood gas, and give a broad-spectrum parenteral antibiotic such as ceftriaxone within the first hour. Administer a 10 to 20 mL per kilogram crystalloid bolus for shock, reassess and repeat with escalation to intensive care for refractory shock. Antibiotic delay is the preventable cause of death, so the antibiotic comes before the cultures return. ^{[8] [9]}

Interpretation of the blood results (3 marks). The platelet count of 45 × 10⁹ per litre, the prolonged prothrombin time, the low fibrinogen and the markedly raised D-dimer indicate disseminated intravascular coagulation driving the purpura fulminans. Apply the ISTH overt disseminated intravascular coagulation score — platelet count, fibrin markers such as D-dimer, prothrombin time and fibrinogen — to grade it. Manage the coagulopathy with haematology-guided fresh-frozen plasma, platelets and, in selected inherited cases, protein C concentrate, alongside treating the sepsis. ^[9]

Disposition and public-health actions (2 marks). Admit to paediatric intensive care or retrieve to a tertiary centre for ongoing resuscitation, blood-product support and, once stable, surgical and burn-unit care for necrotic skin. Notify public health promptly for contact identification and chemoprophylaxis of close contacts, and arrange vaccination review. The diagnosis is clinical and the management has already begun. ^{[8] [9]}