Brief Report: Sensory Reactivity in Children with Phelan-McDermid Syndrome.

Eussen et al. (2016) compared sensory profiles of children with Phelan-McDermid syndrome (PMS) to kids with idiopathic autism. They used parent questionnaires to map how each group reacts to sounds, touch, and other input. The goal was to see if PMS creates a unique sensory signature within the autism spectrum.

Kids with PMS showed more 'low-energy/weak' sensory responses than kids with idiopathic ASD. They also displayed less sensory sensitivity—fewer cover-your-ears moments. In plain words, they seemed under-powered rather than over-reactive.

Ben-Sasson et al. (2009) pooled 14 studies and found that under-responsivity is the biggest sensory red flag for ASD in general. Eussen et al. (2016) zooms in on a genetic subtype and says, 'Yes, but expect even more low-energy signs here.'

Schaaf et al. (2015) tracked smaller pupil reflexes in autistic kids who had more sensory quirks. Their physiologic data line up with M's parent-report data: weak reflexes pair with weak reactivity.

McQuaid et al. (2024) used brain scans to show that autistic youth with high over-responsivity can't tell social from non-social threats. Eussen et al. (2016) found less of that over-responsivity in PMS, hinting the neural route may differ.

If you assess a child with PMS, don't assume the classic autism sensory profile. Plan for low-energy responses: they may not startle, withdraw, or react to pain in expected ways. Use stronger cues, check for missed signals, and teach caregivers to watch for subtle signs of discomfort. Tailoring the plan avoids both under-stimulation and safety risks.