Tissue sections of these brains examined in autopsies show that the brain never developed properly. Another symptom, which seems unrelated to the brain, is kidney malformation. In one family, there were three boys all with the exact same genetic mutation who all had Kallmann's syndrome. One boy had no kidneys and died at birth, the second boy had one kidney and the third boy had both kidneys. A number of genes have overlapping functions.
Some genes are similar and can take over for the defective one.
A molecule that is unique to the migration process is the KAL-1 adhesion molecule. The exact function of the KAL-1 protein is under debate. The standard hypothesis is that it is made by cells in the brain, which guide olfactory nerve axons and LHRH neurons into the brain. In Kallmann's syndrome, the KAL-1 protein does not function properly so the axons and LHRH neurons don't know where to go, he said. So far, no one has identified the receptors on the cells or the axons.