Sinusoidal obstruction syndrome (SOS), historically known as veno-occlusive disease (VOD), is a life-threatening form of liver injury involving the blockage of small blood vessels in the liver.
Clinical Presentation and Diagnosis
For your board exams, it is critical to distinguish SOS from other conditions like Differentiation Syndrome or sepsis. Key clinical markers of SOS include:
- Rapid weight gain and peripheral edema.
- Hyperbilirubinemia (elevated bilirubin).
- Painful hepatomegaly (enlarged liver) and ascites.
- Reversal of portal flow, which can be confirmed via ultrasound.
Drug-Associated Risks
SOS is a well-known side effect of certain antibody-drug conjugates (ADCs) used in leukemia:
- Inotuzumab ozogamicin (Besponsa®): Carries a Black Box Warning for SOS, which occurred in 14% of patients in clinical trials. The risk is particularly high for patients proceeding to an allogeneic hematopoietic stem cell transplant (HCT); therefore, the number of inotuzumab cycles should be limited as much as feasible in those patients.
- Gemtuzumab ozogamicin (Mylotarg®): Associated with SOS, leading to its temporary withdrawal from the market in 2010. Modern protocols now use fractionated dosing (smaller doses over multiple days) to specifically minimize this risk.