We report the cases of two patients with nephropathy that occurred secondary to congenital cyanotic heart disease (CCHD). Few reports have described nephropathy in CCHD (NCCHD) because CCDH patients are usually not followed carefully for urinary abnormalities. Case 1, a 15-year-old girl, was cyanotic and diagnosed as pulmonary atresia immediately after birth. Suspected proteinuria was noted from 9 years old. At age 15, she received renal biopsy. She was diagnosed as NCCHD with segmental lesions caused by microthrombi. Case 2, that of a 14-yearold girl, was diagnosed as complexity of cardiac abnormality by nature and has remained in a condition of cyanosis. Suspected proteinuria was noted from age 12. She received renal biopsy at age 14. This case was diagnosed as NCCHD with intraglomerular megakaryocytes. As the major pathophysiology of NCCHD, hyperviscosity or polycythemia attributable to hypoxia causes an increase of intraglomerular pressure, leading to capillary dilatation or glomerular swelling. Glomerular disorders in CCHD are also reported in association with megakaryocyte infiltration. Usually, megakaryocytes pass through bone marrow sinusoids, enter the systemic venous flow, circulate to the lungs, and shed platelets at the lung. However, megakaryocytes and platelets transported via right to left shunt form microthrombi at glomeruli, release PDGF and or TGF-beta, and increase in the juxtaglomerular cellularity, mesangial cells, and mesangial matrix in CCHD patients. Actually, both our cases revealed segmental glomerular lesions, which are probably associated with megakaryocytes or microthrombi at glomeruli. Our two cases were under hypoxic conditions, but they showed improvement in their urinalysis results and retained normal renal function with treatment using antiplatelet agents and a renin-angiotensin system inhibitor. Risk factors for NCCHD remain indistinct because the backgrounds of underlying diseases, hemodynamics, and medicines vary among CCHD patients. We reported clinicopathological findings related to megakaryocytes or microthrombi in NCCHD. Long-term prognosis of CCHD has improved. The management of NCCHD is important to improve the quality of life in CCHD patients.
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