Congenital nephrotic syndrome is a rare kidney disease which manifests in infants during the first 3 months of life, and is characterized by high levels of protein in the urine (proteinuria), low levels of protein in the blood, and swelling. This disease is primarily caused by genetic mutations which result in damage to components of the glomerular filtration barrier and allow for leakage of plasma proteins into the urinary space. Signs and symptoms
Urine protein loss leads to total body swelling (generalized edema) and abdominal distension in the first several weeks to months of life. Fluid retention may lead to cough (from pulmonary edema), ascites, and widened cranial sutures and fontanelles. High urine protein loss can lead to foamy appearance of urine. Infants may be born prematurely with low birth weight, and have meconium stained amniotic fluid or a large placenta. Complications
Frequent, severe infections: urinary loss of immunoglobulins
Malnutrition and poor growth
Blood clots (hypercoagulability): imbalance of plasma coagulation factors from urine protein loss
Hypothyroidism: urinary loss of thyroid-binding protein
Poor bone health associated with vitamin D deficiency: urinary loss of vitamin D binding protein
Acute kidney injury
Chronic kidney disease and ultimately end-stage kidney disease

Causes
Primary (genetic) causes
Mutations in the following five genes account for greater than 80% of the genetic causes of congenital nephrotic syndrome:
NPHS1 (Finnish Type): The gene NPHS1 encodes for the protein nephrin. This genetic variant is characterized by severe protein loss in the first several days to weeks of life.
Sympathomimetics such as phenylpropanolamine, methylphenidate, and others are also implicated.In pediatric patients varicella inflammation may be followed by vasculitis of intracranial vessels. This condition is called post varicella angiopathy and this may be responsible for arterial ischaemic strokes in children.Several of these vasculitides are associated with antineutrophil cytoplasmic antibodies. These are:

Granulomatosis with polyangiitis
Eosinophilic granulomatosis with polyangiitis
Microscopic polyangiitis

Diagnosis
Laboratory tests of blood or body fluids are performed for patients with active vasculitis. Their results will generally show signs of inflammation in the body, such as increased erythrocyte sedimentation rate (ESR), elevated C-reactive protein (CRP), anemia, increased white blood cell count and eosinophilia. Other possible findings are elevated antineutrophil cytoplasmic antibody (ANCA) levels and hematuria. Other organ functional tests may be abnormal. Specific abnormalities depend on the degree of various organs involvement. A brain SPECT can show decreased blood flow to the brain and brain damage. The definite diagnosis of vasculitis is established after a biopsy of involved organ or tissue, such as skin, sinuses, lung, nerve, brain, and kidney. The biopsy elucidates the pattern of blood vessel inflammation.Some types of vasculitis display leukocytoclasis, which is vascular damage caused by nuclear debris from infiltrating neutrophils. It typically presents as palpable purpura. Conditions with leucocytoclasis mainly include hypersensitivity vasculitis (also called leukocytoclastic vasculitis) and cutaneous small-vessel vasculitis (also called cutaneous leukocytoclastic angiitis).An alternative to biopsy can be an angiogram (x-ray test of the blood vessels). It can demonstrate characteristic patterns of inflammation in affected blood vessels.