Biography is a special case of classification. There are dedicated memos about classifying biographies in the subject headings manual as well as the classification and shelflisting manual (F 275, G 320).
A reading of these instructions will show that biographies can’t be placed wherever one would like, there has to be a provision provided for it in the schedule.
Turning again to the HVs, the first such instruction encountered under ‘People with disabilities’ is at HV1552.3
Including persons involved with rehabilitation or education of and services to people with disabilities
For individual biography, see the specific class of people with disabilities
The specific classes provided are as follows:
Including works on the deaf and blind
Deaf. Hearing impaired
Terminally ill. Incurables
People with mental disabilities
People with physical disabilities
Of these six, biography provisions are given for people with blindness (and those of exceptional pupils), deafness, and terminal illnesses.
Biographies for people with mental disabilities are directed to RC569.7-574*, and biographies for people with physical disabilities are also directed to see the condition itself in the R [Medicine] class.
So to sum up: when classifying a book about someone with disabilities, depending on the disability your options are to class it as a biography under a class of people needing ‘Protection, assistance, relief’ — or to place it alongside all medical works on the same condition. As disabled activists advocate for decreasing the medicalized view, we do a disservice with these two options.
*While there is a provision at HV3006.A39.A-Z for Biography, individual, A-Z, checking LC’s catalog reveals a total of 7 books with that classification. That indicates to me that the preferred area is RC569.7-574.