Blood Group: Kidd
Common: 26% Caucasians, 51% Blacks, 23% Asians are Jkb- and at risk for developing anti-Jkb 
Causes HDN: Yes
Critical Titer: 1:16
Anti-Jkb is rarely associated with severe HDN, even with high titers. As of 2014, only 13 cases have been reported, so the possible reasons for that still remain unclear. Most of HDN due to anti-Jkb are mild-to-moderate, and usually have a good prognosis. 
Anti-Jkb usually displays mild clinical symptoms. This article however reports the second case of HDN due to anti-Jkb with severe symptoms and a fatal outcome. The infant was admitted at 4 days old being lethargic and having high pitched crying. The total bilirubin was 46.1 mg/dL.  It should be noted that iso bilirubin peaks days 4-6. This infant was at the peak time, and the high pitched crying is a sign of kernicterus (brain damage due to bilirubin), which can be fatal. The authors say that pediatricians should be aware of the course of hemolytic jaundice due to anti-Jkb and be ready to treat with active therapeutic interventions .
1 - https://www.ncbi.nlm.nih.gov/books/NBK2272/
2 - https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2733965/