What’s causing this patient’s spontaneous laughter?

A four-year-old girl is referred to a pediatric neurologist with new-onset generalized tonic-clonic seizures. Her father mentions that she has also had sudden episodes of spontaneous unexplained loud laughter for the past year, and they now occur almost daily. Neurological examination is unremarkable. An MRI reveals the findings seen here. Which of the following other clinical features is commonly associated with this patient’s condition?

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What substance is associated with this presentation?

A 45-year-old female presents with painful lesions on her lower limbs and ears. She is a smoker, and has a history of recreational drug use. Purpuric, necrotic lesions are noted on both lower extremities, in addition to tender purpura on both ears. A biopsy is performed which demonstrates leukocytoclastic vasculitis. Use of which substance is most likely to be associated with this presentation?

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