Major or Mild Neurocognitive Disorder Due to Huntington’s Disease 639
D. The neurocognitive disorder is not attribut able to another medical condition and is not
better explained by another mental disorder.
Coding note:  For major neurocognitive disorder due to Huntington’s disease, with behav-
ioral disturbance, code first 333.4 (G10)  Huntington’s disease, followed by 294.11
(F02.81)  major neurocognitive disorder due to Huntington’s disease, with behavioral dis-
turbance. For major neurocognitive disorder due to Huntington’s disease, without behav-
ioral disturbance, code first 333.4 (G10)  Huntington’s disease, followed by 294.10 (F02.80)
major neurocognitive disorder due to Huntington’s disease, without behavioral disturbance.
For mild neurocognitive disorder due to Huntington’s disease, code 331.83 (G31.84).
(Note:  Do not use the additional code for Huntington’s disease. Behavioral disturbance
cannot be coded but should still be indicated in writing.)
Diagnostic Features
Progressive cognitive impairment is a core feature of Huntington ’s disease, with early changes
in executive function (i.e., processing speed, organization, and planni ng) rather than learn-
ing and memory. Cognitive and associated beha vioral changes often precede the emergence
of the typical motor abnormalities of bradykinesia (i.e., slowing of voluntary movement)
and chorea (i.e., involuntary jerking movements). A diagnosis of definite Huntington’s dis-
ease is given in the presence of unequivocal,  extrapyramidal motor ab normalities in an in-
dividual with either a family history of Huntington’s disease or genetic testing showing a
CAG trinucleotide repeat expansion in the HTT gene, located on chromosome 4.