Amyotrophic Lateral Sclerosis (ALS): ALS is a progressive neurodegenerative disease that affects nerve cells in the brain and spinal cord, leading to loss of muscle control. It often presents with asymmetrical distal weakness without hard sensory findings, making it the most likely diagnosis given the symptoms.

Mononeuropathy Multiplex: This condition involves damage to multiple peripheral nerves, which can cause weakness, usually in a patchy or asymmetrical pattern. While it can present with sensory findings, the absence of hard sensory findings does not rule it out, as the primary complaint can sometimes be weakness.
Vitamin E Deficiency: Vitamin E deficiency can lead to neurological symptoms, including weakness. However, it is less common and typically associated with other systemic signs of deficiency.

Vitamin B12 Deficiency: Although less likely to present with purely asymmetrical distal weakness without sensory findings, vitamin B12 deficiency can cause a range of neurological symptoms, including weakness. It is crucial to consider this diagnosis because it is treatable and can have severe consequences if left untreated.

Other rare conditions that might present with similar symptoms include certain types of muscular dystrophy, mitochondrial myopathies, or very rare neurodegenerative diseases. These would be considered if the more common diagnoses are ruled out and the clinical presentation is highly suggestive of a specific rare condition.