C9orf72 and Splenomegaly: While occasional mild splenomegaly was observed in the 2 month old C9orf72 deficient mice, this phenotype becomes more severe with age, with the 4-5 month old C9orf72 deficient mouse having a spleen 2-3 times the size of its littermate control (Fig. 5d and Additional file 4: Figure S3).