Ask-Upmark kidney is a rare diagnosis of segmental hypoplasia in pediatric population clinically characterized by severe hypertension potentially treatable with partial to total nephrectomy. Although originally was described only as a congenital anomaly, recent data suggest to be caused by vesicoureteral reflux, either in utero or in early childhood and pyelonephritis. The case we reported indicates that Ask-Upmark kidney should be considered as potential cause of hypertension and renal failure both in children and adults. The renal biopsy is necessary for early diagnosis and may consent to normalize blood pressure with nephrectomy; however, if renal damage is severe and progressive with tubulointerstitial nephritis, surgical management is excluded and renal transplant should be considered.