A patient with Papillon-Lefèvre syndrome (palmo-plantar hyperkeratosis with periodontosis) had involvements also of the knees, elbows, and fingernails. This is the third reported case in Japan, and this patient did not have abnormal calcification inside the skull.
Ohkawara A, Miura Y, Ishikawa J. Papillon-Lefèvre Syndrome. Arch Dermatol. 1974;109(5):726-728. doi:10.1001/archderm.1974.01630050064018