Intellectual Disability

A 6-year-old boy from rural Maharashtra is brought to the paediatric clinic by his mother with concerns about delayed development. The child sat independently at 18 months, walked at 2.5 years, and speaks only 10–15 words at age 6. He attends a regular school but cannot follow two-step commands and requires assistance with toileting. On examination, he has a broad nasal bridge, short stature (height <3rd percentile), and a single palmar crease bilaterally. His mother reports that she had poor antenatal care and no iodine supplementation during pregnancy. Thyroid function tests show TSH 8.2 mIU/L (normal <5) and free T4 0.8 ng/dL (normal 0.8–1.8). What is the most likely aetiology of this child's intellectual disability?

A 7-year-old boy is brought to the paediatric clinic by his mother with concerns about delayed development. He attends a mainstream school but requires significant support in academics and self-care. On examination, he has a broad nasal bridge, upslanting palpebral fissures, and a single palmar crease bilaterally. His IQ is measured at 52 on standardized testing. His mother reports he was born to non-consanguineous parents and has no significant perinatal complications. What is the most likely diagnosis?

An 8-year-old girl is referred to the child psychiatry clinic by her school teacher for concerns about learning difficulties and behavioural problems. The child's developmental history reveals that she achieved major milestones within normal limits until age 3 years, after which her parents noticed progressive loss of purposeful hand skills, loss of language, and onset of repetitive hand-wringing movements. She now has severe intellectual disability (IQ 25), does not speak, and engages in self-injurious behaviour. On examination, she has microcephaly, spasticity in all four limbs, and hyperreflexia. EEG shows generalized spike-and-wave discharges. Brain MRI reveals cerebral atrophy and white matter changes. What is the most likely diagnosis?

A 5-year-old girl is referred to the developmental pediatrics clinic for assessment of global developmental delay. Her mother reports she was born at term with no perinatal complications. She sat independently at 18 months, walked at 30 months, and speaks in single words only. On examination, she has microcephaly, hypertelorism, and a high-arched palate. Neuroimaging shows cortical dysplasia with polymicrogyria. Her IQ is estimated at 28. The mother denies any family history of developmental disorders. What is the most appropriate next step in management?

A 7-year-old boy is brought to the child psychiatry clinic by his parents with concerns about delayed development. He attained sitting at 12 months and walking at 24 months. He speaks in 2–3 word phrases and has difficulty understanding complex instructions. On examination, he has a broad nasal bridge, upslanting palpebral fissures, and a single palmar crease bilaterally. His IQ on formal testing is 42. The parents report he has been attending a special school for the past 2 years. What is the most likely diagnosis?