The ordinary two and four year limits on reopening may not apply if the claimant was suffering from serious mental illness at the time of the prior denial. If it is determined that the claimant was unrepresented at the time of the prior denial and lacked the mental competence to pursue an appeal, SSA is required to reopen the old claim no matter how far back it may go. SSR 91-5p; see POMS GN 03101.020; memorandum from chief administrative law Judge to all OHA Field Personnel, March 21, 1990, Reminders, reprinted in relevant part in 12 Social Security forum, No. 2 (March 1990) at 11. )
