An injury or illness must be work-related to be covered under OSHA Injury and Illness Recordkeeping requirements (29 CFR 1904). That is, a causal connection must exist between the employment and the injury of illness for a case to be recordable.
OSHA has concluded that the employer is in the best position to determine work-relatedness, not an M.D. or the OSHA inspector. However, inspectors may second-guess employers, so you might consider erring on the side of caution. Use your best judgment, being aware that the consequences of over-reporting are minimal whereas underreporting can result in citations as well as a negative impression of the workplace on the part of the OSHA inspector.
OSHA considers an injury or illness to be work-related if an event or exposure in the work environment either caused or contributed to the resulting condition or significantly aggravated a pre-existing injury or illness. Work-relatedness is presumed for an injury or illness resulting from events of exposures occurring in the work environment, unless an exception in Section 1904.5(b)(2) specifically applies or the employer can prove it is a pre-existing condition and nothing in the workplace aggravated it.