use strict;
use warnings;

my %AB;
while (<DATA>) {
     chomp;
     my ($id, $name, $desc, $app) = split /\s*,\s*/;
     $AB{$id}{app}      .= ",$app";
     $AB{$id}{name_desc} = "$name, $desc";
}

for (keys %AB) { $AB{$_}{app} =~ s/^,// } # remove leading comma

for my $id (sort keys %AB) {
    print "$id, $AB{$id}{name_desc}, $AB{$id}{app} \n";
}

__DATA__
1, XYZ, desc, PDF
1, XYZ, desc, QFZ
2, YGH, desc, LMN