Hypeensive crises in younger children are usually secondary to an underlying disease. Commonest cause of systemic hypeension in children is:

Renal disease is the most common cause of secondary hypeension in children. They include, Glomerulonephritis HUS Chronic infections Obstructive lesions Renal vascular disease Other causes: Endocrine causes of hypeension include, Tumors that secrete vasoactive peptides (pheochromocytoma) Abnormal levels of endogenous steroid hormones (Cushing syndrome) Adrenocoical steroid therapy Hypehyroidism Congenital hea disease such as coarctation of the aoa Elevated intracranial pressure Exogenous medications or toxins Ref: Koerner C.E. (2011). Chapter 128. Renal Emergencies in Infants and Children. In J.E. Tintinalli, J.S. Stapczynski, D.M. Cline, O.J. Ma, R.K. Cydulka, G.D. Meckler (Eds), Tintinalli's Emergency Medicine: A Comprehensive Study Guide, 7e.