State Medical Board Improvement Act of 1990

State Medical Board Improvement Act of 1990 - Amends part B (Peer Review) of title XI of the Social Security Act to require that a peer review organization (PRO) notify the State board responsible for licensing or disciplining a physician when the PRO makes any findings respecting such physician or sends such physician an initial notice of its proposed sanction against such physician. Requires the Secretary of Health and Human Services to notify the State board responsible for licensing a physician of a decision to exclude such physician from providing health care services under the Social Security Act on a reimbursable basis. Amends title XIX (Medicaid) of the Social Security Act to require a State to notify the State medical licensing board when a person is prohibited from participating in, or otherwise sanctioned under, the Medicaid program. Amends title XVIII (Medicare) of the Social Security Act to require Medicare carriers to refer a case involving a physician's unethical or unprofessional conduct to the State medical board responsible for licensing such physician.