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]

SAQ 2 (10 marks)

Question: A previously well four-year-old boy is brought with three days of increasing bruising over the limbs and a petechial rash over the ankles, with two episodes of epistaxis. He is afebrile, active and cheerful, with no hepatosplenomegaly or lymphadenopathy. His full blood count shows a haemoglobin of 124 g per litre, a white-cell count of 7.2 × 10⁹ per litre, a neutrophil count of 3.1 × 10⁹ per litre, and a platelet count of 12 × 10⁹ per litre, with a normal film showing no blasts. (a) What is the most likely diagnosis, and which features exclude leukaemia? (b) Outline the management, including when you would treat. (c) What safety-netting and follow-up will you give? (10 marks) [3]

Model answer

(a) Diagnosis and exclusion of leukaemia (3 marks). The most likely diagnosis is acute immune thrombocytopenia (ITP). The child is well, has sudden bruising and petechiae with an otherwise normal examination, and the full blood count shows isolated thrombocytopenia — a platelet count of 12 × 10⁹ per litre, under the 100 × 10⁹ per litre threshold of the standard definition. Leukaemia is excluded by the normal haemoglobin, white-cell and neutrophil counts, the absence of blasts on the film, and the absence of hepatosplenomegaly and lymphadenopathy; isolated thrombocytopenia with pancytopenia or blasts would not be ITP. [3] [1]

(b) Management and when to treat (4 marks). ITP management is risk-based, matching treatment to the bleeding severity rather than to the platelet count alone. With only bruising and minor epistaxis (dry purpura), observation and safety-netting may be reasonable, though many clinicians treat when the count is very low. When treatment is indicated — active or wet bleeding, a very low count, or high-risk activities — first-line options are a short course of corticosteroids, intravenous immunoglobulin, or anti-D immunoglobulin in an Rh-positive, non-splenectomised child. Avoid steroids if any atypical feature is present, because they can mask leukaemia; here the film is clean, so treatment is appropriate if the bleeding warrants it. [2] [1]

(c) Safety-netting and follow-up (3 marks). Counsel the family to avoid contact sports, vigorous play and intramuscular injections while the count is low, and give written safety-netting to return immediately for head injury, excessive or uncontrolled bleeding, new petechial spread, or any neurological symptom suggesting intracranial haemorrhage. Arrange haematology follow-up, because most acute childhood ITP resolves within months while persistent and chronic disease is managed with haematology. Reassure the family that serious bleeding is uncommon but is the event the safety-netting exists to catch. [2] [1]