Aphantasia rarely shows up alone. Autism, ADHD, sensory differences, eating disorders, face blindness, even fibromyalgia come up alongside it, though none are known to cause the others.
Dance and colleagues · Consciousness and Cognition
Across two large samples, grapheme-color synesthesia was as common in people with aphantasia as in others. In a separate study, 118 people with aphantasia reported more autistic traits than controls, mainly in imagination and social skills.