Here are those patterns cut-and-paste ready, just select the number of consecutive letters you want to match:
To match 2 consecutive lowercase letters:
(?:ab|bc|cd|de|ef|fg|gh|hi|ij|jk|kl|lm|mn|no|op|pq|qr|rs|st|tu|uv|vw|wx|xy|yz)
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To match 2 consecutive uppercase letters:
(?:AB|BC|CD|DE|EF|FG|GH|HI|IJ|JK|KL|LM|MN|NO|OP|PQ|QR|RS|ST|TU|UV|VW|WX|XY|YZ)
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To match 2 consecutive lowercase and uppercase letters:
(?:ab|bc|cd|de|ef|fg|gh|hi|ij|jk|kl|lm|mn|no|op|pq|qr|rs|st|tu|uv|vw|wx|xy|yz|AB|BC|CD|DE|EF|FG|GH|HI|IJ|JK|KL|LM|MN|NO|OP|PQ|QR|RS|ST|TU|UV|VW|WX|XY|YZ)
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To match 3 consecutive lowercase letters:
(?:abc|bcd|cde|def|efg|fgh|ghi|hij|ijk|jkl|klm|lmn|mno|nop|opq|pqr|qrs|rst|stu|tuv|uvw|vwx|wxy|xyz)
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To match 3 consecutive uppercase letters:
(?:ABC|BCD|CDE|DEF|EFG|FGH|GHI|HIJ|IJK|JKL|KLM|LMN|MNO|NOP|OPQ|PQR|QRS|RST|STU|TUV|UVW|VWX|WXY|XYZ)
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To match 3 consecutive lowercase and uppercase letters:
(?:abc|bcd|cde|def|efg|fgh|ghi|hij|ijk|jkl|klm|lmn|mno|nop|opq|pqr|qrs|rst|stu|tuv|uvw|vwx|wxy|xyz|ABC|BCD|CDE|DEF|EFG|FGH|GHI|HIJ|IJK|JKL|KLM|LMN|MNO|NOP|OPQ|PQR|QRS|RST|STU|TUV|UVW|VWX|WXY|XYZ)
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To match 4 consecutive lowercase letters:
(?:abcd|bcde|cdef|defg|efgh|fghi|ghij|hijk|ijkl|jklm|klmn|lmno|mnop|nopq|opqr|pqrs|qrst|rstu|stuv|tuvw|uvwx|vwxy|wxyz)
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To match 4 consecutive uppercase letters:
(?:ABCD|BCDE|CDEF|DEFG|EFGH|FGHI|GHIJ|HIJK|IJKL|JKLM|KLMN|LMNO|MNOP|NOPQ|OPQR|PQRS|QRST|RSTU|STUV|TUVW|UVWX|VWXY|WXYZ)
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To match 4 consecutive lowercase and uppercase letters:
(?:abcd|bcde|cdef|defg|efgh|fghi|ghij|hijk|ijkl|jklm|klmn|lmno|mnop|nopq|opqr|pqrs|qrst|rstu|stuv|tuvw|uvwx|vwxy|wxyz|ABCD|BCDE|CDEF|DEFG|EFGH|FGHI|GHIJ|HIJK|IJKL|JKLM|KLMN|LMNO|MNOP|NOPQ|OPQR|PQRS|QRST|RSTU|STUV|TUVW|UVWX|VWXY|WXYZ)
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To match 5 consecutive lowercase letters:
(?:abcde|bcdef|cdefg|defgh|efghi|fghij|ghijk|hijkl|ijklm|jklmn|klmno|lmnop|mnopq|nopqr|opqrs|pqrst|qrstu|rstuv|stuvw|tuvwx|uvwxy|vwxyz)
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To match 5 consecutive uppercase letters:
(?:ABCDE|BCDEF|CDEFG|DEFGH|EFGHI|FGHIJ|GHIJK|HIJKL|IJKLM|JKLMN|KLMNO|LMNOP|MNOPQ|NOPQR|OPQRS|PQRST|QRSTU|RSTUV|STUVW|TUVWX|UVWXY|VWXYZ)
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To match 5 consecutive lowercase and uppercase letters:
(?:abcde|bcdef|cdefg|defgh|efghi|fghij|ghijk|hijkl|ijklm|jklmn|klmno|lmnop|mnopq|nopqr|opqrs|pqrst|qrstu|rstuv|stuvw|tuvwx|uvwxy|vwxyz|ABCDE|BCDEF|CDEFG|DEFGH|EFGHI|FGHIJ|GHIJK|HIJKL|IJKLM|JKLMN|KLMNO|LMNOP|MNOPQ|NOPQR|OPQRS|PQRST|QRSTU|RSTUV|STUVW|TUVWX|UVWXY|VWXYZ)
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To match 6 consecutive lowercase letters:
(?:abcdef|bcdefg|cdefgh|defghi|efghij|fghijk|ghijkl|hijklm|ijklmn|jklmno|klmnop|lmnopq|mnopqr|nopqrs|opqrst|pqrstu|qrstuv|rstuvw|stuvwx|tuvwxy|uvwxyz)
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To match 6 consecutive uppercase letters:
(?:ABCDEF|BCDEFG|CDEFGH|DEFGHI|EFGHIJ|FGHIJK|GHIJKL|HIJKLM|IJKLMN|JKLMNO|KLMNOP|LMNOPQ|MNOPQR|NOPQRS|OPQRST|PQRSTU|QRSTUV|RSTUVW|STUVWX|TUVWXY|UVWXYZ)
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To match 6 consecutive lowercase and uppercase letters:
(?:abcdef|bcdefg|cdefgh|defghi|efghij|fghijk|ghijkl|hijklm|ijklmn|jklmno|klmnop|lmnopq|mnopqr|nopqrs|opqrst|pqrstu|qrstuv|rstuvw|stuvwx|tuvwxy|uvwxyz|ABCDEF|BCDEFG|CDEFGH|DEFGHI|EFGHIJ|FGHIJK|GHIJKL|HIJKLM|IJKLMN|JKLMNO|KLMNOP|LMNOPQ|MNOPQR|NOPQRS|OPQRST|PQRSTU|QRSTUV|RSTUVW|STUVWX|TUVWXY|UVWXYZ)
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To match 7 consecutive lowercase letters:
(?:abcdefg|bcdefgh|cdefghi|defghij|efghijk|fghijkl|ghijklm|hijklmn|ijklmno|jklmnop|klmnopq|lmnopqr|mnopqrs|nopqrst|opqrstu|pqrstuv|qrstuvw|rstuvwx|stuvwxy|tuvwxyz)
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To match 7 consecutive uppercase letters:
(?:ABCDEFG|BCDEFGH|CDEFGHI|DEFGHIJ|EFGHIJK|FGHIJKL|GHIJKLM|HIJKLMN|IJKLMNO|JKLMNOP|KLMNOPQ|LMNOPQR|MNOPQRS|NOPQRST|OPQRSTU|PQRSTUV|QRSTUVW|RSTUVWX|STUVWXY|TUVWXYZ)
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To match 7 consecutive lowercase and uppercase letters:
(?:abcdefg|bcdefgh|cdefghi|defghij|efghijk|fghijkl|ghijklm|hijklmn|ijklmno|jklmnop|klmnopq|lmnopqr|mnopqrs|nopqrst|opqrstu|pqrstuv|qrstuvw|rstuvwx|stuvwxy|tuvwxyz|ABCDEFG|BCDEFGH|CDEFGHI|DEFGHIJ|EFGHIJK|FGHIJKL|GHIJKLM|HIJKLMN|IJKLMNO|JKLMNOP|KLMNOPQ|LMNOPQR|MNOPQRS|NOPQRST|OPQRSTU|PQRSTUV|QRSTUVW|RSTUVWX|STUVWXY|TUVWXYZ)
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To match 8 consecutive lowercase letters:
(?:abcdefgh|bcdefghi|cdefghij|defghijk|efghijkl|fghijklm|ghijklmn|hijklmno|ijklmnop|jklmnopq|klmnopqr|lmnopqrs|mnopqrst|nopqrstu|opqrstuv|pqrstuvw|qrstuvwx|rstuvwxy|stuvwxyz)
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To match 8 consecutive uppercase letters:
(?:ABCDEFGH|BCDEFGHI|CDEFGHIJ|DEFGHIJK|EFGHIJKL|FGHIJKLM|GHIJKLMN|HIJKLMNO|IJKLMNOP|JKLMNOPQ|KLMNOPQR|LMNOPQRS|MNOPQRST|NOPQRSTU|OPQRSTUV|PQRSTUVW|QRSTUVWX|RSTUVWXY|STUVWXYZ)
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To match 8 consecutive lowercase and uppercase letters:
(?:abcdefgh|bcdefghi|cdefghij|defghijk|efghijkl|fghijklm|ghijklmn|hijklmno|ijklmnop|jklmnopq|klmnopqr|lmnopqrs|mnopqrst|nopqrstu|opqrstuv|pqrstuvw|qrstuvwx|rstuvwxy|stuvwxyz|ABCDEFGH|BCDEFGHI|CDEFGHIJ|DEFGHIJK|EFGHIJKL|FGHIJKLM|GHIJKLMN|HIJKLMNO|IJKLMNOP|JKLMNOPQ|KLMNOPQR|LMNOPQRS|MNOPQRST|NOPQRSTU|OPQRSTUV|PQRSTUVW|QRSTUVWX|RSTUVWXY|STUVWXYZ)
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To match 9 consecutive lowercase letters:
(?:abcdefghi|bcdefghij|cdefghijk|defghijkl|efghijklm|fghijklmn|ghijklmno|hijklmnop|ijklmnopq|jklmnopqr|klmnopqrs|lmnopqrst|mnopqrstu|nopqrstuv|opqrstuvw|pqrstuvwx|qrstuvwxy|rstuvwxyz)
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To match 9 consecutive uppercase letters:
(?:ABCDEFGHI|BCDEFGHIJ|CDEFGHIJK|DEFGHIJKL|EFGHIJKLM|FGHIJKLMN|GHIJKLMNO|HIJKLMNOP|IJKLMNOPQ|JKLMNOPQR|KLMNOPQRS|LMNOPQRST|MNOPQRSTU|NOPQRSTUV|OPQRSTUVW|PQRSTUVWX|QRSTUVWXY|RSTUVWXYZ)
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To match 9 consecutive lowercase and uppercase letters:
(?:abcdefghi|bcdefghij|cdefghijk|defghijkl|efghijklm|fghijklmn|ghijklmno|hijklmnop|ijklmnopq|jklmnopqr|klmnopqrs|lmnopqrst|mnopqrstu|nopqrstuv|opqrstuvw|pqrstuvwx|qrstuvwxy|rstuvwxyz|ABCDEFGHI|BCDEFGHIJ|CDEFGHIJK|DEFGHIJKL|EFGHIJKLM|FGHIJKLMN|GHIJKLMNO|HIJKLMNOP|IJKLMNOPQ|JKLMNOPQR|KLMNOPQRS|LMNOPQRST|MNOPQRSTU|NOPQRSTUV|OPQRSTUVW|PQRSTUVWX|QRSTUVWXY|RSTUVWXYZ)
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To match 10 consecutive lowercase letters:
(?:abcdefghij|bcdefghijk|cdefghijkl|defghijklm|efghijklmn|fghijklmno|ghijklmnop|hijklmnopq|ijklmnopqr|jklmnopqrs|klmnopqrst|lmnopqrstu|mnopqrstuv|nopqrstuvw|opqrstuvwx|pqrstuvwxy|qrstuvwxyz)
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To match 10 consecutive uppercase letters:
(?:ABCDEFGHIJ|BCDEFGHIJK|CDEFGHIJKL|DEFGHIJKLM|EFGHIJKLMN|FGHIJKLMNO|GHIJKLMNOP|HIJKLMNOPQ|IJKLMNOPQR|JKLMNOPQRS|KLMNOPQRST|LMNOPQRSTU|MNOPQRSTUV|NOPQRSTUVW|OPQRSTUVWX|PQRSTUVWXY|QRSTUVWXYZ)
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To match 10 consecutive lowercase and uppercase letters:
(?:abcdefghij|bcdefghijk|cdefghijkl|defghijklm|efghijklmn|fghijklmno|ghijklmnop|hijklmnopq|ijklmnopqr|jklmnopqrs|klmnopqrst|lmnopqrstu|mnopqrstuv|nopqrstuvw|opqrstuvwx|pqrstuvwxy|qrstuvwxyz|ABCDEFGHIJ|BCDEFGHIJK|CDEFGHIJKL|DEFGHIJKLM|EFGHIJKLMN|FGHIJKLMNO|GHIJKLMNOP|HIJKLMNOPQ|IJKLMNOPQR|JKLMNOPQRS|KLMNOPQRST|LMNOPQRSTU|MNOPQRSTUV|NOPQRSTUVW|OPQRSTUVWX|PQRSTUVWXY|QRSTUVWXYZ)
