Her son is dying. She hopes the FDA will let her try to save him.

In the end, Shannon Moyer McNeil could do nothing to save her children. The Northern Virginia mother lost her daughter Waverly just after she turned 12 and her son Oliver three years later, just before his 12th birthday. Both children were diagnosed with a rare genetic condition called Sanfilippo syndrome. “November and December are challenging times for my family,” McNeil, who lives in Alexandria, told me recently. Within those months, she explained, fall the dates of her children’s births and deaths.