INTRODUCTION:In 1932 Panton and Valentine first described a Staphylococcal exotoxin that they classed as a leukocidin. It is an important virulence factor inducing leukocyte hemolysis by pore forming activity as well as necrosis by local release of inflammatory components and is associated with primary skin infections and severe necrotizing pneumonia.
CASE PRESENTATION:We present a 30 year old Caucasian female with a history of thalassemia minor who had flu like symptoms for a week and productive cough for 2 days prior to being broughtto the ER with worsening lethargy, shortness of breath and fever. On examination, temperature was 102, BP: 90/50, heart rate: 135, respiratory rate: 24 and oxygensaturation of 73% on room air and 94% on 100% high flow oxygen. Systemic examination was significant for bilateral rhonchi on auscultation of lungs and she was in severe respiratory distress. Her white count was 2600 with 44% bands, hematocrit 36.4, haemoglobin 11.9, platelet count 150,000, Sodium 135, potassium 3, chloride98, bicarbonate20, BUN 20, creatinine 1.5, glucose 149. Patient was also found to be 7 weeks pregnant. Nasal washings for influenza culture were positive, blood cultures grew methicillin sensitive staphylococcus aureus with the genomic study identifying the PVL gene.The patient was started on oxacillin 2 gms IV every 4hours. Patient’s hospital course was complicated by development of ARDS requiring prone ventilation, sepsis, rhabdomyolysis (CPK > 300,000) and oliguric acute renal failure requiring hemodialysis. A repeat ultrasonogram indicated a nonviable pregnancy. CT thorax done 5 days later showed mild residual infiltrate at left lung base with extensive bilateral bullous formation in both lungs replacing previous infiltrates with bullous disease consistent with pneumatocoele formation.
DISCUSSIONS:The PVL-associated necrotizing pneumonia differs from usual community acquired Staphylococcus aureus pneumonia in that the population is younger1, healthy1 and the evolution is often rapidly fatal despite intensive medical management1. The PVL gene can be found in both MRSA and MSSA2. Necrotizing hemorrhagic pneumonia manifests in the early phase as a flu-like illness and is later characterized by hemoptysis, fever, tachycardia, hypotension with marked leukopenia, high CRP, raised creatinine kinase and multilobar infiltrates on chest x-ray.Another interesting finding in our patient was the presence of pneumatocoeles, which are usually seen in children especially with Staphylococcus aureus pneumonia. Mechanism is generally via inflammation and narrowing of the bronchus, leading to the formation of an endobronchial ball valve, which ultimately leads to distal dilatation of the bronchi and alveoli. As the surrounding consolidation resolves, the pneumatocoeles become more apparent and/or enlarge, usually seen during the resolution stage of pneumonitis.
CONCLUSION:The presence of hemoptysis, leukopenia and pneumatocoele formation are highly suggestive of lethal PVL-positive Staphylococcus aureus necrotizing pneumonia. Early use of anti-staphylococcal antibiotic therapy is the only validated approach, however, the disease is fulminant with a mean mortality rate of 75%2. Intravenous immunoglobulin (in-vitro inhibits the cytotoxicity of staphylococcal leukocidins on polymorphonuclear leukocytes), clindamycin and linezolid (arrest toxin production) have also been tried in severe cases2. Management of pneumatocoele is supportive with treatment of the underlying condition with appropriate antibiotics. Pneumatocoeles rarely require surgical resection.
DISCLOSURE:Ali Kanchwala, No Financial Disclosure Information; No Product/Research Disclosure Information