**Background:** Purpura fulminans (PF) in neonates is a rare, life-threatening condition characterized by thrombosis, organ necrosis, and gangrene, often due to infectious or congenital deficiencies of protein C or S. Congenital chylothorax, the most common cause of fetal pleural effusion, leads to loss of lymphocytes, antibodies, and coagulation factors, yet PF has not been previously reported in this context. This case report describes a female neonate who developed PF after drainage of congenital chylothorax and also suffered bilateral retinal detachments, expanding the spectrum of complications.
**Methods:** A term female infant (37 weeks, 2.775 kg) with antenatally detected bilateral pleural effusion (95% lymphocytes on aspiration) was delivered by cesarean section for breech presentation and maternal HELLP syndrome. At birth, she required resuscitation and thoracocentesis (10 ml right, 49 ml left serous fluid), later bilateral chest tube insertion for pneumothoraces. At 12 hours of age, she developed well-demarcated erythematous macules progressing to blue-black purpuric lesions on face, abdomen, and arms. Septic markers were normal; cultures and PCR for herpesviruses were negative. Coagulation testing showed low protein C (0.07 U/ml at 17 h), protein S antigen (0.27 U/ml), protein S activity (0.21 U/ml), and antithrombin (0.15 U/ml), with elevated D-dimer (4.45 mg/L at 20 h) and ISTH DIC score of 7. Platelet counts dropped from 226 × 10⁹/L at 1 h to 41 × 10⁹/L at 43 h. FFP was transfused every 12 h on day 1, once on day 2, and discontinued on day 3. On day 4, coagulation factors normalized, and PF resolved. Genetic testing (RAPID exome) revealed a variant of unknown significance in PAK2 (c.1115A>T, p.Asp732Val) but no mutations in PROC, PROS, or SERPINC1. Ophthalmological examination at discharge (due to absent red reflex) included dilated fundus exam, fluorescein angiography, and B-scan ultrasound, confirming bilateral retinal detachments (funnel in right eye, knife-edge in left eye) without neovascularization.
**Key Results:** The neonate’s protein C levels increased from 0.07 U/ml (17 h) to 0.11 U/ml (20 h) post-FFP, and antithrombin from 0.15 U/ml to 0.19 U/ml at 48 h. PF lesions resolved without recurrence. Platelet counts recovered to 177 × 10⁹/L by 150 h. Bilateral retinal detachments were confirmed; no retinoblastoma, cataract, or calcifications were seen. Genetic testing did not identify pathogenic variants in PROC, PROS, or SERPINC1.
**Clinical Implications:** This case demonstrates that drainage of congenital chylothorax can precipitate transient deficiency of protein C, S, and antithrombin, leading to purpura fulminans. Prompt recognition and FFP replacement led to resolution. The bilateral retinal detachment, novel in this association, may result from thrombotic events or other mechanisms such as familial exudative vitreoretinopathy. Clinicians should monitor coagulation factors in neonates with chylothorax, consider prophylactic FFP, and perform early ophthalmological assessment. The PAK2 variant identified is of unknown significance and warrants further investigation.