Haim-Munk syndrome is an extremely rare autosomal recessive disorder of keratinization characterized clinically by palmoplantar hyperkeratosis, severe early onset periodontitis, onychogryphosis, pes planus, arachnodactyly, and acro-osteolysis. Recently, germline mutations in the lysosomal protease cathepsin C gene have been identified as the underlying genetic defect in Haim-Munk syndrome and in the clinically related disorders, Papillon-Lefèvre syndrome and prepubertal periodontitis.