Neurofibromatosis tumours grow from the nerves' support cells, not neurons
Neurofibromatosis is not one disease but three genetic conditions that seed tumours along the nervous system. Oddly, the growths come from the cells that wrap and support nerves rather than from neurons. Half of cases are inherited; the other half arise from fresh mutations early in development.
The three conditions are type 1, type 2 and schwannomatosis. Most of their tumours are benign, though some turn cancerous, and symptoms are often mild. Type 1 typically shows up as café au lait patches of light brown skin, small bumps in or under the skin called neurofibromas, a sideways curve of the spine and headaches; around 60 percent of affected children have mild trouble at school. Type 2's signature is hearing loss, caused by tumours pressing on the acoustic nerve, sometimes with tinnitus, balance problems and cataracts. Schwannomatosis mainly means pain where tumours press on nerves.
Each type traces to a different faulty gene. Type 1 involves the NF1 gene on chromosome 17, which makes neurofibromin, a protein that normally reins in cell division. Type 2 involves a tumour suppressor on chromosome 22 that produces merlin, a regulator of growth factors. Schwannomatosis stems from the SMARCB1 gene, which sits near the NF2 gene; that proximity once led researchers to think the two conditions were the same. All three are autosomal dominant, so a child of an affected parent has a 50 percent chance of inheriting it, and a parent's mild case can become a child's severe one or the reverse.
In the United States roughly 1 in 3,500 people have type 1, 1 in 25,000 type 2 and 1 in 40,000 schwannomatosis, with men and women affected equally. Type 1 usually appears before age 10 and most people with it live a normal lifespan. Type 2 may stay hidden until early adulthood and raises the risk of early death.
No prevention or cure exists. Troublesome or malignant tumours can be removed surgically or treated with radiation and chemotherapy, and cochlear or brainstem implants can help with hearing. Descriptions that seem to match the condition go back to the 1st century, but the first formal account came in 1882 from Friedrich Daniel von Recklinghausen, whose name the disease once carried.
Source: Neurofibromatosis
