I have the below SQL query:

select distinct HospitalAcctID,
        AdmitDate,
        DischargeDate,
        PatMRN,
        Pat_id,
        ICD,
        MedCenter,
        (case when SeqCount =1 and AdmitDate > '06/01/2013'   and AdmitDate < '06/01/2018' then 1 else null end ) Firstdiag
    from
    (
    select distinct acct.HSP_ACCOUNT_ID as HospitalAcctID,
        cast(acct.ADM_DATE_TIME as date format 'mm/dd/yyyy') as AdmitDate,
        cast(acct.DISCH_DATE_TIME as date format 'mm/dd/yyyy') as DischargeDate,
        pat.pat_mrn_id as PatMRN,
        pat.pat_id as Pat_id,
        REF_BILL_CODE as ICD,
        grp7.NAME AS MedCenter,
        row_number() over (partition by PatMRN order by AdmitDate) as SeqCount
        from   acct 
        inner join  pat on pat.pat_id = acct.pat_id
        inner join  hspenc on hspenc.CSN_ID = acct.CSN_ID
        inner join  dx  on acct.ACCOUNT_ID = dx.ACCOUNT_ID and line = 1
        inner join  edg on dx.DX_ID = edg.DX_ID
        inner join loc on loc.LOC_ID = acct.LOC_ID
        inner join  grp7 ON loc.RPT_GRP_SEVEN = grp7.RPT_GRP_SEVEN
        where
        grp7.NAME =  'SMC AREA'
        and ADMIT_CONF_STAT_C in ('1','4')
        and (edg. REF_BILL_CODE in ('431',
                        '431')                                      
                )                   
    and ADT_PAT_CLASS_C in ('1204','12113')
    order by  AdmitDate;
    ) Admit

But I am getting a syntax error

Syntax error, expected something like an 'EXCEPT' keyword, 'UNION' Keyword or a 'MINUS' keyword between 'AdmitDate' and ','

In the outer select statement, I am trying to get the min (first ) date when the was first diagnosed. I also want to get only the patients who were diagnosed between 6/2013 to 6/2018 which is why I have the CASE expression. But the CASE expression is giving me an error.