Which symptom is commonly associated with L1 syndrome?

L1 syndrome, also known as X-linked hydrocephalus, is primarily associated with various neurological and physical features that arise from mutations in the L1CAM gene. One of the hallmark symptoms of this syndrome is impaired smell, which is tied to the neurological effects of the condition. This impairment can be attributed to the involvement of the olfactory bulb and its pathways, which are affected in individuals with L1 syndrome.

While other symptoms may be present in individuals with L1 syndrome, such as micropenis, thrombocytopenia, and coarse facial features, these are not the most characteristic or commonly associated symptoms. Impaired smell stands out as a signature symptom linked to the condition's pathophysiology, making it the most pertinent choice in this context. Thus, the correct answer reflects a deeper understanding of the neurological implications of L1 syndrome as related to olfactory function.