PHOX2B and sudden infant death syndrome: In another study, 12 (55%) out of 22 SIDS cases with normal PHOX2B polyalanine repeat showed a decreased amount of PHOX2B positive stained neurons in the RTN compared to age-matched controls.51 The authors hypothesized that some SIDS cases might be explained by unknown PHOX2B mutations or mutations in the PHOX2B pathway.