The progression of the condition is roughly as follows:

Congenital musculoskeletal disorders may or may not be present
Cutaneous conditions may be observed in early infancy
Small tumors may arise in the retina which can eventually lead to blindness. Also, Lisch Nodules may grow on the iris, but these are harmless. Learning disabilities may arise in preschool children
Neurofibromas may occur and can sometimes cause many dependent neurological conditions and cutaneous and skeletal disfigurement. Depression and social anxiety may occur as a result of disabilities caused by the condition
Neurofibromas may, in 8-13% of cases, transition into cancer, which can be fatal The NF Clinical Program at St. Louis Childrens Hospital maintains a comprehensive list of current NF research studies Archived 2015-11-26 at the Wayback Machine. Musculoskeletal disorder
Musculoskeletal abnormalities affecting the skull include sphenoid bone dysplasia, congenital hydrocephalus and associated neurologic impairment. These abnormalities are non-progressive and may be diagnosed in the fetus or at birth.Disorders affecting the spine include:

In NF-1, there can be a generalized abnormality of the soft tissues in the fetus, which is referred to as mesodermal dysplasia, resulting in maldevelopment of skeletal structures. Meningoceles and formation of cystic diverticula of the dura of the spine, unrelated to Spina bifida
Radiographically, dural ectasia can lead to scalloping of the posterior vertebral bodies and to the formation of cystic diverticula of the dura of the spine. This may result in temporary or permanent loss of lower extremity sensorimotor function. Focal scoliosis and/or kyphosis are the most common skeletal manifestation of NF-1, occurring in 20% of affected patients.
Injury to the lower chest can cause injuries to the spleen and liver.A scaphoid abdomen is when the abdomen is sucked inwards. In a newborn, it may represent a diaphragmatic hernia. In general, it is indicative of malnutrition. Disease
Many gastrointestinal diseases affect the abdominal organs. These include stomach disease, liver disease, pancreatic disease, gallbladder and bile duct disease; intestinal diseases include enteritis, coeliac disease, diverticulitis, and IBS. Examination
Different medical procedures can be used to examine the organs of the gastrointestinal tract. These include endoscopy, colonoscopy, sigmoidoscopy, enteroscopy, oesophagogastroduodenoscopy and virtual colonoscopy. There are also a number of medical imaging techniques that can be used. Surface landmarks are important in the examination of the abdomen. Surface landmarks
In the mid-line a slight furrow extends from the xiphoid process above to the pubic symphysis below, representing the linea alba in the abdominal wall. At about its midpoint sits the umbilicus or navel. The rectus abdominis on each side of the linea alba stands out in muscular people. The outline of these muscles is interrupted by three or more transverse depressions indicating the tendinous intersections. There is usually one about the xiphoid process, one at the navel, and one in between. It is the combination of the linea alba and the tendinous intersections which form the abdominal "six-pack" sought after by many people. The upper lateral limit of the abdomen is the subcostal margin (at or near the subcostal plane) formed by the cartilages of the false ribs (8, 9, 10) joining one another.