This patient's symptoms are consistent with adult attention-deficit/hyperactivity disorder (ADHD), characterized by a persistent pattern of inattention and/or hyperactivity-impulsivity that interferes with functioning. First-line pharmacologic treatment for ADHD in adults is a stimulant medication, such as methylphenidate or amphetamine. Sertraline is an SSRI for depression/anxiety, lorazepam is a benzodiazepine for anxiety, and risperidone is an antipsychotic.

Primary progressive aphasia (PPA) is a clinical dementia syndrome characterized by the gradual and prominent decline in language abilities, while other cognitive domains like memory and executive function are relatively spared early in the disease course. PPA is considered a form of frontotemporal lobar degeneration. This contrasts with typical Alzheimer disease (early memory loss) and behavioral-variant FTD (early personality and behavioral changes).

While cognitive deficits like memory impairment and executive dysfunction are present in both dementia and delirium, the hallmark features that distinguish delirium are its acute onset (hours to days) and a fluctuating course of symptoms, with variations in attention and arousal level throughout the day. The slow, progressive decline is characteristic of the underlying neurocognitive disorder (dementia), while the recent, rapid change with fluctuations points to delirium.

In patients with ADHD and a co-occurring substance use disorder, particularly with a history of diversion, non-stimulant medications are preferred. Atomoxetine, a norepinephrine reuptake inhibitor, is an effective and FDA-approved non-stimulant treatment for ADHD and lacks abuse potential. Stimulants like amphetamine-dextroamphetamine would be a poor choice due to the high risk of abuse and diversion.

This patient presents with an insidious onset and gradual progression of cognitive decline, primarily affecting recent memory (amnestic presentation) and executive function. This clinical picture in an elderly individual is classic for Alzheimer disease, the most common cause of dementia. The absence of stepwise decline, parkinsonism, hallucinations, or prominent early personality changes makes other dementia subtypes less likely.

HIV-associated neurocognitive disorder (HAND) is a common complication in patients with advanced HIV/AIDS (typically CD4 < 200). It characteristically presents as a subcortical dementia with symptoms of apathy, executive dysfunction, and psychomotor slowing. Other opportunistic infections like PML, CNS lymphoma, and toxoplasmosis typically present more acutely with focal neurological deficits and show characteristic focal lesions on MRI.

This patient's presentation includes the core features of dementia with Lewy bodies (LBD): fluctuating cognition, well-formed visual hallucinations, and parkinsonism. The presence of REM sleep behavior disorder (acting out dreams) is also highly suggestive. In LBD, cognitive decline begins before or within one year of the onset of motor symptoms. In Parkinson disease dementia, dementia develops more than one year after the diagnosis of Parkinson disease.

The clinical picture of early and prominent personality change (disinhibition), apathy, and altered food preferences with relatively preserved memory is characteristic of the behavioral variant of frontotemporal dementia (bvFTD). This condition is caused by focal neurodegeneration in the frontal and temporal lobes.

This patient has an acute change in mental status superimposed on her chronic dementia, which is highly suggestive of delirium. The most important initial step is to identify and treat the underlying medical cause. In elderly patients, infections such as urinary tract infections or pneumonia are common precipitants. Therefore, an infection workup including urinalysis, CBC, and chest x-ray is the most appropriate next step.

This child displays the core features of autism spectrum disorder (ASD): 1) persistent deficits in social communication and social interaction (impaired eye contact, lack of response to name, no pretend play), and 2) restricted, repetitive patterns of behavior, interests, or activities (spinning wheels, insistence on sameness). While he has developmental delay, the specific pattern of deficits points to ASD.