Alliteration algorithm

A function to determine is a string is an alliteration, for example
" as albert asked Anna, an antelope appeared!" is considered to be one.

private static bool IsAnAlliteration(string subject)
{
  bool result = true;

  char lead = default(char);

  bool inWord = false;

  foreach (char c in subject)
  {
    char current = char.ToLower(c);

    bool isLetter = char.IsLetter(current);
    // lead contains first character in string
    // all words should start with lead character
    if (lead == default(char) && isLetter)
      lead = current;

    if (!inWord && isLetter && lead != current)
      result = false; // start of new word, but does not start with lead char
    else if (!inWord && isLetter && lead == current)
      inWord = true; // start of new word starts with lead char
    else if (inWord && char.IsWhiteSpace(current))
      inWord = false; // end of word found

    if (!result)
      break;
  }
  // did we find at least one word
  result &= (lead != default(char));

  return result;
}