Nyctalopia Due to Vitamin A Deficiency Secondary to Short Bowel Syndrome: When the Electroretinogram Is the Diagnostic Key

<b>Background:</b> Vitamin A deficiency (VAD) can occur due to malnutrition or reduced intestinal absorption, such as in short bowel syndrome (SBS). The main causes of SBS in adults include post-radiotherapy and surgery (e.g., repeated bowel resections). VAD mostly involves rods producing nyctalopia and reduced amplitudes of the electroretinogram (ERG) in scotopic conditions, with a characteristic negative ERG pattern (b/a < 1). <b>Case Report:</b> We report a 67-year-old woman with a history of gastric adenocarcinoma and several surgeries, who developed a progressive 3-month clinical picture of night blindness. <b>Results</b>: Urgent blood tests, biomicroscopy, intraocular pressure measurements, fundoscopy, and a cranial MRI were all normal. Visual evoked potentials showed increased latencies in both eyes, and full-field ERG showed a significant alteration in responses under scotopic conditions, and, to a lesser extent, under photopic conditions. Laboratory tests confirmed VAD, probably due to post-surgery and radiotherapy SBS. After parenteral vitamin replacement, VAD was clinically, analytically, and electroretinographically resolved. <b>Discussion:</b> VAD diagnosis is based on history, neuro-ophthalmological examination, and serum levels of retinol (<0.3 µg/mL) and/or retinol/retinol-binding protein (<0.8). In cases of a history of SBS, acquired nyctalopia, negative ERG, and clinical, analytical, and electroretinographic improvement with restoration of vitamin A levels, VAD should be suspected. ERG is crucial for early and appropriate management. <b>Conclusions:</b> As far as we know, this is the first reported VAD case secondary to SBS following surgical resections and radiotherapy of gastric adenocarcinoma with neuro-ophthalmological, laboratory, and electroretinographic monitoring of VAD recovery.