NU104 Unit 3 Case Study Analysis Example

Ten Days After a Sore Throat: A Case Study Analysis of Post-Streptococcal Glomerulonephritis in a Composite 8-Year-Old, Classified as a Type III Hypersensitivity and Traced From Infection to Cola-Colored Urine

[Student Name]

Purdue University Global

NU104: Pathophysiology for Nursing

Unit 3 Case Study Analysis

[Instructor Name]

[Date]

The child and family are composite; laboratory values are typical of the condition and bracketed where they are illustrative.

The Case

[Mateo], a composite 8-year-old, is brought to the clinic because his eyelids have been puffy for two mornings and his urine looks "like cola." His mother reports a sore throat with fever about ten days ago that improved without treatment. Today his blood pressure is [138/88] mm Hg, high for his age, and he has mild swelling of both ankles. Urinalysis shows blood and red cell casts, with a small amount of protein. His serum creatinine is [0.9] mg/dL, about twice his expected value, and his complement C3 level is low. An antibody test for streptococcal infection is positive.

Classifying the Reaction

The pattern fits post-streptococcal glomerulonephritis, and the reaction behind it is a type III hypersensitivity, mediated by immune complexes. In type I reactions, IgE on mast cells causes immediate symptoms such as hives or wheezing within minutes. In type II reactions, antibodies bind directly to antigens fixed on a particular cell or tissue, as in a mismatched transfusion. In type IV reactions, T cells rather than antibodies cause damage over one to three days, as in poison ivy. Type III differs from all three: antibodies combine with soluble antigens in the blood to form complexes, and the damage occurs where those complexes are deposited, often far from where the antigen first appeared (Rogers, 2023). Mateo's throat infection was the source of the antigen; his kidney was where the complexes lodged.

From First Exposure to Symptom

The sequence explains the ten-day gap. Certain strains of group A Streptococcus, called nephritogenic strains, produce proteins that the immune system recognizes as foreign. During the throat infection, Mateo's B cells began producing antibodies against those proteins, a process that takes one to two weeks for a new antigen. As antibody levels rose, antibodies met circulating streptococcal antigens and formed immune complexes. Some antigens may also have lodged in the glomerular basement membrane first, with antibodies binding to them there (Balasubramanian & Marks, 2017).

The glomerulus is especially exposed to this kind of damage. It filters a large volume of blood through a fine capillary network under pressure, so complexes in the circulation are carried to its walls and trapped. Once deposited, the complexes activate complement, a cascade of plasma proteins. Complement fragments attract neutrophils and monocytes, and the inflammatory cells release enzymes and oxygen radicals that injure the capillary walls. The cells lining the glomerulus also multiply, narrowing the capillaries.

The kidney is injured not because it was infected, but because it filters the blood that carries the immune complexes.

Connecting Each Finding to Its Cause

The ten-day delay matches the time needed to make antibodies against a new antigen. A type I reaction would have occurred within minutes, and the infection itself would have produced symptoms at the time of the sore throat, not after it had resolved.

Dark, cola-colored urine and red cell casts come from blood leaking through damaged glomerular capillaries. Red cells pass into the tubules, where they are packed together into casts by tubular protein; casts prove the bleeding started in the kidney rather than lower in the urinary tract.

The low C3 level reflects complement being consumed as it binds to the deposited complexes faster than the liver can replace it. In most children it returns to normal within about eight weeks, which is one of the features that distinguishes this condition from other forms of glomerulonephritis (Balasubramanian & Marks, 2017).

The raised creatinine shows that filtration has fallen. Inflamed, narrowed glomerular capillaries filter less plasma, so creatinine, which the kidney clears by filtration, builds up in the blood.

Puffy eyelids, ankle swelling and high blood pressure all stem from the same cause: with filtration reduced, the kidney retains sodium and water. The extra volume raises blood pressure and leaks into loose tissues, which in a child lying flat overnight shows first around the eyes. This is a different kind of edema from that seen when large amounts of protein are lost, because here the main problem is retained salt and water rather than low blood protein.

The small amount of protein in the urine reflects leakage through the damaged filter. Heavy protein loss would point toward a different diagnosis.

Ruling Out Look-Alikes

Two other conditions can bring a child to clinic with blood in the urine soon after a sore throat, and the timing separates them. In IgA nephropathy, dark urine appears within a day or two of the infection, while the throat is still sore, because IgA-containing complexes form quickly; complement levels are usually normal. In Mateo's case the urine darkened ten days later and C3 is low, which fits the post-streptococcal pattern. Nephrotic syndrome also causes puffy eyes in children, but it brings heavy protein loss, very low blood albumin and usually no high blood pressure or red cell casts; Mateo's protein loss is small and his blood pressure is raised. A review of the condition notes that a low C3 that returns to normal within weeks, together with evidence of a recent streptococcal infection, is the usual basis for the diagnosis, with biopsy reserved for children whose course is atypical (Rodriguez-Iturbe & Musser, 2008). Biopsy, when done, shows the immune deposits as lumps on the outer side of the glomerular basement membrane.

Why This Child and Not Others

Many children have strep throat, and few develop kidney disease. Only certain strains are nephritogenic, and individual differences in how the immune system responds to those antigens also appear to matter. Treating the throat infection does not reliably prevent the kidney reaction, because by the time symptoms appear the antibody response is already underway. The condition is now uncommon in high-income countries but remains frequent where streptococcal skin and throat infections are widespread and access to care is limited (Balasubramanian & Marks, 2017).

Course and Nursing Relevance

Most children recover fully. Treatment supports the kidney while the inflammation settles: limiting salt and fluid, controlling blood pressure, and sometimes a diuretic. Nurses monitor daily weight, intake and output, blood pressure and urine color, since rising weight or blood pressure signals fluid overload. Families are told that blood in the urine may remain visible under a microscope for months after the child feels well, which is expected rather than a sign of relapse.

References

Balasubramanian, R., & Marks, S. D. (2017). Post-infectious glomerulonephritis. Paediatrics and International Child Health, 37(4), 240-247. https://doi.org/10.1080/20469047.2017.1369642

Rodriguez-Iturbe, B., & Musser, J. M. (2008). The current state of poststreptococcal glomerulonephritis. Journal of the American Society of Nephrology, 19(10), 1855-1864. https://doi.org/10.1681/ASN.2008010092

Rogers, J. L. (Ed.). (2023). McCance & Huether's pathophysiology: The biologic basis for disease in adults and children (9th ed.). Elsevier.