Case Report: Elastography-negative acute fatty liver of pregnancy diagnosed by histopathology and electron microscopy

Acute fatty liver of pregnancy (AFLP) is a rare pregnancy-related liver disorder that can rapidly progress to multiorgan failure, including disseminated intravascular coagulation (DIC) and renal dysfunction. It is potentially fatal if not promptly recognized and treated; however, the diagnostic role of imaging modalities remains poorly defined. We report a case of a 29-year-old primigravida who presented with progressive jaundice, liver dysfunction, coagulopathy, and renal impairment at 33 weeks of gestation. Abdominal computed tomography (CT) demonstrated decreased hepatic attenuation, with a CT value of 23.0 Hounsfield units, suggestive of fatty deposition. Based on fulfillment of 7 of the 14 Swansea criteria and the presence of fetal distress, an emergency cesarean section was performed. On postoperative day 18, the controlled attenuation parameter (CAP) obtained by vibration-controlled transient elastography indicated a steatosis grade of S0, with a CAP value of 196 dB/m, whereas ultrasound-guided liver biopsy revealed microvesicular steatosis on histological examination, confirmed by adipophilin immunostaining. Electron microscopy further demonstrated numerous microvesicular lipid droplets and dilatation of the rough endoplasmic reticulum, leading to a definitive diagnosis of AFLP. This case suggests that CAP may underestimate hepatic fat accumulation when steatosis is predominantly microvesicular, as in AFLP, and that detailed pathological and ultrastructural evaluation may be valuable for diagnostic confirmation and improved understanding of disease pathophysiology.