Neurofibromatosis.

Neurofibromatosis is usually inherited (dominant inheritance) disorder that is associated with skin lesions, molluscum fibrosum. Pigmented areas may occur with the condition. Although the name implies neural tumours, it is believed to be a multi-system disorder and can occasionally resemble polyostotic fibrous dysplasia, (which is usually without an inherited component and is typically asymmetric in the body involvement). Occasionally, there may even be hypophosphataemic osteomalacia in Neurofibomatosis. Bone abnormalities include growth processes. Bones or parts of bones may be larger or smaller. The bone texture can be coarsened and there may be pressure erosions on the bone from neighbouring neurofibromas. The spectacular pseudarthrosis of the tibia is commoner in textbooks. There is an increased incidence of renal artery stenosis in this condition and an increased incidence of Phaeochromocytoma, meningeoma and accoustic neuroma.

In the spine, there may be enlargement of the foramina by neurofibromas and meningocoeles with scalloping of the posterior borders of the vertebral bodies. The skull base may be small for its (normal) contents and a deficiency of the posterior wall of the orbit (sphenoid) may be present (especially if you're given a skull in an exam situation).