Psych · intellectual-disability
Behavioural phenotypes and genetic syndromes
Also known as Behavioural phenotype genetic syndrome · Down syndrome psychiatry · Fragile X psychiatric phenotype · Prader-Willi psychosis · Angelman syndrome behaviour · 22q11.2 deletion syndrome psychiatry · Velocardiofacial syndrome schizophrenia · VCFS psychosis risk · DiGeorge psychiatric
Exam-exhaustive behavioural phenotypes of genetic syndromes for FRANZCP and global boards: probabilistic phenotype concept; Down syndrome depression and Alzheimer dementia; fragile X full mutation and premutation spectrum; Prader-Willi hyperphagia and UPD-associated psychosis; Angelman severe ID and seizures; 22q11.2DS/VCFS highest monogenic CNV psychosis risk; genetics work-up; psychopharmacology caveats in ID.
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Red flags
- New cognitive or functional decline in adult Down syndrome without excluding depression, hypothyroidism, sensory loss and sleep apnoea
- First-episode psychosis in learning disability with cardiac or palatal history — consider 22q11.2DS
- Psychosis in Prader-Willi — check genetic subtype; maternal UPD carries highest psychosis risk
- Uncontrolled food access in Prader-Willi — life-threatening gorging and choking risk
- Diagnostic overshadowing: attributing all new behaviour to the syndrome and missing treatable illness or abuse
- Starting antipsychotics for communication-driven behaviour without functional analysis or medical screen
Meet the patient
A 19-year-old young man with known Prader-Willi syndrome is brought by his parents after he became convinced that staff at his day service were "putting thoughts into his head." Over six months he has slept poorly, become increasingly rigid about routines, and gained weight after finding an unsecured food store. His parents ask, plainly: "Is this part of the syndrome, or is he ill?"[7][8]
That question — syndrome or illness? — is the entire topic in one sentence. The fellowship answer is that it is both at once: the syndrome raises the prior probability, but you still diagnose and treat the psychiatric disorder present today.[1][7][8]
References15ShowHide
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- [2]Di Nuovo S, Buono S Behavioral phenotypes of genetic syndromes with intellectual disability: comparison of adaptive profiles Psychiatry Res, 2011.PMID 21507490
- [3]Antonarakis SE, Skotko BG, Rafii MS, et al. Down syndrome Nat Rev Dis Primers, 2020.PMID 32029743
- [4]Zigman WB, Lott IT Alzheimer's disease in Down syndrome: neurobiology and risk Ment Retard Dev Disabil Res Rev, 2007.PMID 17910085
- [5]Holland AJ, Hon J, Huppert FA, Stevens F, Watson P Population-based study of the prevalence and presentation of dementia in adults with Down's syndrome Br J Psychiatry, 1998.PMID 9828989
- [6]Hagerman RJ, Berry-Kravis E, Hazlett HC, et al. Fragile X syndrome Nat Rev Dis Primers, 2017.PMID 28960184
- [7]Cassidy SB, Schwartz S, Miller JL, Driscoll DJ Prader-Willi syndrome Genet Med, 2012.PMID 22237428
- [8]Boer H, Holland A, Whittington J, Butler J, Webb T, Clarke D Psychotic illness in people with Prader Willi syndrome due to chromosome 15 maternal uniparental disomy Lancet, 2002.PMID 11809260
- [9]Williams CA, Beaudet AL, Clayton-Smith J, et al. Angelman syndrome 2005: updated consensus for diagnostic criteria Am J Med Genet A, 2006.PMID 16470747
- [10]Murphy KC, Jones LA, Owen MJ High rates of schizophrenia in adults with velo-cardio-facial syndrome Arch Gen Psychiatry, 1999.PMID 10530637
- [11]Schneider M, Debbané M, Bassett AS, et al. Psychiatric disorders from childhood to adulthood in 22q11.2 deletion syndrome: results from the International Consortium on Brain and Behavior in 22q11.2 Deletion Syndrome Am J Psychiatry, 2014.PMID 24577245
- [12]Bassett AS, McDonald-McGinn DM, Devriendt K, et al. Practical guidelines for managing patients with 22q11.2 deletion syndrome J Pediatr, 2011.PMID 21570089
- [13]McDonald-McGinn DM, Sullivan KE, Marino B, et al. 22q11.2 deletion syndrome Nat Rev Dis Primers, 2015.PMID 27189754
- [14]Malhotra D, Sebat J CNVs: harbingers of a rare variant revolution in psychiatric genetics Cell, 2012.PMID 22424231
- [15]Miller DT, Adam MP, Aradhya S, et al. Consensus statement: chromosomal microarray is a first-tier clinical diagnostic test for individuals with developmental disabilities or congenital anomalies Am J Hum Genet, 2010.PMID 20466091