SSDI (Social Security Disability Insurance) and SSI (Supplemental Security
Income) are both federal programs that provide benefits to individuals with disabilities, but they differ significantly in eligibility requirements and how they are funded. 

SSDI requires a work history and is funded by payroll taxes, while SSI is need-based and doesn't require a work history. Once a person qualifies for SSI or MCCW they should also get Medicaid. 

https://www.ssa.gov/ssi
SSI provides monthly payments to people with disabilities and older adults who have little or no income or resources.
www.ssa.gov
There is a list for compassionate allowances - Compassionate Allowances are a way to quickly identify diseases and other medical conditions that, by definition, meet Social Security's standards for disability benefits. If a patient has one of the listed diagnoses
the process will be much quicker.