HDD patients develop multifocal fibromatosis:
arms, breast, paraspinal muscles, occiput, lower ribs, abdominal wall, and
mesentery. Desmoid tumors may proliferate in various areas: arms, ribs,
breasts, occiput, mesentery, abdominal wall, and paraspinal muscles.
Epidermal cysts and osteomata of the skull and mandible, as well as
scoliosis caused by desmoid disease, have been described. Desmoid tumors are
not considered malignant per se, but their local aggressiveness and
recurrence after surgical removal are frequent. Although some families with
HDD are predisposed to colonic carcinoma, colonic polyposis is rare. Up to
90% of FAP patients have congenital hypertrophy of the retinal pigment
epithelium (<40% of control patients).