Medication-induced tremors: Given the patient's history of asthma, they may be on medications such as beta-agonists or corticosteroids, which can cause tremors as a side effect. Additionally, medications used to manage autism or associated symptoms could also contribute to tremors.

Anxiety or stress-related tremors: Individuals with autism may experience heightened levels of anxiety or stress, which can manifest physically as tremors.
Essential tremor: Although less common in younger populations, essential tremor could be a consideration, especially if there's a family history.
Vitamin deficiencies: Deficiencies in vitamins such as B12 can cause neurological symptoms including tremors, and individuals with autism may have dietary restrictions or difficulties that increase the risk of such deficiencies.

Wilson's disease: A genetic disorder that leads to copper accumulation in the body, causing neurological symptoms including tremors. It's crucial to diagnose early as it can be treated.
Thyroid disorders: Both hyperthyroidism and hypothyroidism can cause tremors. Given the potential for autoimmune thyroid disease in individuals with asthma, this is an important consideration.
Neurodegenerative diseases: Early onset Parkinson's disease or other neurodegenerative conditions, although rare, could present with tremors and must be considered to ensure appropriate management.

Heavy metal poisoning: Exposure to heavy metals like mercury or lead can cause tremors among other neurological symptoms. This might be considered if there's a known exposure history.
Mitochondrial disorders: These are a group of disorders caused by dysfunctional mitochondria, which can lead to a variety of neurological symptoms, including tremors.
Autoimmune encephalitis: A rare condition where the body's immune system attacks the brain, potentially causing tremors along with other neurological and psychiatric symptoms.