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Which disease family does the family history point to (Parkinson's, FTD, Huntington's), so which gene?
More, if you want it
What illness did the patient's parent have?Tap a term: its definition, what you can do with it, and how often the exam asks it.
Definition: the Huntington's disease gene, changed by a CAG repeat on chromosome 4.
You can: Tell HTT from SNCA by the parent's illness of movement, memory and mood change.
Definition: the alpha-synuclein gene on chromosome 4, a rare dominant cause of Parkinson's disease.
You can: Tell SNCA from LRRK2 by how rare the dominant Parkinson's form is.
Definition: the commonest dominant gene in familial Parkinson's disease, on chromosome 12.
You can: Tell LRRK2 from PRKN, PINK1 and DJ-1 by dominant or recessive inheritance.
Definition: genes for recessive early-onset Parkinson's disease.
You can: Name PRKN, PINK1 and DJ-1 when Parkinson's disease starts early and both parents are well.
Definition: the commonest familial frontotemporal dementia gene, a repeat on chromosome 9.
You can: Tell C9orf72 from MAPT by chromosome 9 or chromosome 17.
Definition: the tau gene on chromosome 17, a cause of frontotemporal dementia with parkinsonism.
You can: Tell MAPT from GRN by frontotemporal dementia with parkinsonism.
Definition: the progranulin gene on chromosome 17, a cause of familial frontotemporal dementia.
You can: Name GRN when a chromosome 17 gene for progranulin causes frontotemporal dementia.
Each card is one term. The grey line is what the patient says, which is what the question stem gives.
Summary
HTT is also called IT-15.
Huntington's disease is caused by a in the HTT gene on chromosome 4, at 4p16.3. HTT is also called IT-15.
Huntington's disease is one of the few single-gene, autosomal dominant disorders in psychiatry. An affected parent is expected. The CAG codon codes for glutamine, so the change is called a triplet repeat. Onset is typically in middle life, though adolescent cases occur. A CAG-repeat expansion is a run of the three bases CAG copied too many times. HTT makes the protein huntingtin. Candidates see clumsy movements and pick SNCA, the Parkinson's gene.
Rhys Pritchard sits in a neurogenetics clinic in Cardiff. Rhys has clumsy movements, low mood and memory trouble. Rhys says, "My dad died in a care home with the same illness."
A person with a movement disorder, cognitive decline and psychiatric change needs a family history check. A family history of a similar illness, especially in a parent, raises suspicion of Huntington's disease.
Wilson disease also causes a movement disorder, psychosis and personality change. Serum copper is low in Wilson disease, and a dominant family history is absent.
7 more sections on Huntington's, Parkinson's and frontotemporal dementia genes: HTT, SNCA, LRRK2, C9orf72, MAPT, GRN and more
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