A 3-year-old previously healthy boy presented with a fever (39.5°C), tonsillitis, cervical lymphadenopathy and epistaxis. Laboratory testing showed elevated C reactive protein (73 mg/L/695.2 nmol/L), leukocytosis (16 G/L), mild thrombocytopenia (138 G/L) and anaemia (haemoglobin 96 g/L). Within 24 hours, he developed gross haematuria and progressive irregular purpuric skin lesions affecting the lower extremities (figure 1), an elbow and genitals, typical of purpura fulminans. Antimicrobial therapy with third-generation cephalosporin and clindamycin was initiated. Laboratory testing for acute bacterial, fungal and viral infections was negative. Coagulation tests revealed disseminated intravascular coagulation (DIC) with prolonged prothrombin time (international normalised ratio >5.39), activated partial thromboplastin time (>170 s), thrombin time (>120s), undetectable fibrinogen (80000 pg/L). Inspired by a previous case, protein S levels were checked and protein S deficiency (11) was identified. Antibody testing (Hyphen Biomed) detected IgG anti-protein S antibody of 100 AU/mL (reference <10 AU/mL) (day 2) declining to 11 AU/mL (day 13) and 4 AU/mL (day 43) after initial presentation.
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