20 C.F.R. § 416.933

We may make a finding of presumptive disability or presumptive blindness if the evidence available at the time we make the presumptive disability or presumptive blindness finding reflects a high degree of probability that you are disabled or blind. In the case of readily observable impairments (e.g., total blindness), we will find that you are disabled or blind for purposes of this section without medical or other evidence. For other impairments, a finding of disability or blindness must be based on medical evidence or other information that, though not sufficient for a formal determination of disability or blindness, is sufficient for us to find that there is a high degree of probability that you are disabled or blind. For example, for claims involving the human immunodeficiency virus (HIV), the Social Security Field Office may make a finding of presumptive disability if your medical source provides us with information that confirms that your disease manifestations meet the severity of listing-level criteria for HIV. Of course, regardless of the specific HIV manifestations, the State agency may make a finding of presumptive disability if the medical evidence or other information reflects a high degree of probability that you are disabled.