It is caused by premature closure of all cranial sutures, because the skull growth is restricted in all directions except for the fontanelle, so the head grows upward in a tower shape. The skull base is sunken by pressure, the orbits become shallow, the eyes protrude, and the paranasal sinuses are poorly developed. Due to the extension of brain tissue in the vertical direction, the upper and lower skull diameters increase, the anterior and posterior diameters become shorter, the anterior cranial fossa can be shortened to 1.5 cm, the optic nerve foramen becomes smaller, the supraorbital fissure is short, the cerebral gyrus indentation increases significantly, the butterfly saddle expands, and the closure of fontanelle is delayed. The frontal bone is retracted or posteriorly rotated, so that the frontal bone and the nasal crest are connected into a line, and the frontal-nasal angle disappears. The typical case is a cranial acromion. Posterior rotation of the frontal bone is the main cause of cranial deformity. The middle of the face may be normal. It is worth pointing out that acromegaly does not show significant clinical manifestations until the age of 2 to 3 years, because in many cases the skull is normal at the age of 1 year and the typical acromegaly appears only at the age of 4 years. True acromegaly with juxtaposed finger/toe deformities of the hands or feet is called Saethre-Chotzen syndrome. Fatty chondrodysplasia is characterized by hypochondroplasia, optic nerve atrophy, a large head with a wide and flat nose and thick lips, and also belongs to the acromegaly category.