What is the Difference Between Cystinuria and Cystinosis

The key difference between cystinuria and cystinosis is that cystinuria is an autosomal recessive condition that causes urine to become quickly supersaturated with cystine, which may precipitate out as pathognomonic hexagonally-shaped crystals, whereas cystinosis is an autosomal recessive disorder that causes cystine to accumulate in the lysosomes of proximal tubule cells.

Cysteine is a non-essential amino acid important for making proteins and for other metabolic functions in the body. This amino acid is found in beta keratin. Beta keratin is the main protein in nails, skin, and hair. Cystinuria and cystinosis are two different hereditary conditions. Both of these conditions are genetic and involve the amino acid cysteine. They are autosomal recessive conditions. But they have different pathogeneses.

CONTENTS

1. Overview and Key Difference
2. What is Cystinuria 
3. What is Cystinosis
4. Similarities – Cystinuria and Cystinosis
5. Cystinuria vs. Cystinosis in Tabular Form
6. FAQ – Cystinuria and Cystinosis
7. Summary – Cystinuria vs. Cystinosis

What is Cystinuria?

Cystinuria is an inherited disease that causes stones made out of cystine to form in the kidneys, bladder, and ureters. Cystinuria typically occurs in approximately 1 in every 10,000 people worldwide. It is an autosomal recessive condition in which there is a mutation in a dibasic amino acid transporter that is normally expressed at the apical surface of the tubular lumen. This condition is due to mutations of two genes such as SLC3A1 and SLC7A9. Moreover, the symptoms of this condition are blood in the urine, severe pain in the side or the back, nausea, vomiting, and pain near the groin, pelvis, or abdomen.

Cystinuria can be diagnosed through urine tests, intravenous pyelogram, abdominal CT scan, and genetic testing. Furthermore, treatment options for cystinuria may include dietary changes, adjusting pH balance, medications such as chelating agents, and surgery.

What is Cystinosis?

Cystinosis is a hereditary disease caused by a mutation in the CTNS gene. This gene encodes a lysosomal transporter of the amino acid cysteine. Without this transporter, cystine accumulates in the lysosomes of proximal tubule cells of the kidney. Ultimately, this leads to cell toxicity. Moreover, the symptoms of this condition are excessive thirst, excessive urination, electrolyte imbalance, vomiting, dehydration, fever, rickets, growth delay or failure to thrive, scarred corneas, light sensitivity, vision loss, difficulty swallowing, fatigue, muscle weakness, myopathy, short stature, delayed puberty, and infertility.

Cystinosis can be diagnosed through blood tests, genetic testing, urinalysis, and eye examination. Furthermore, treatment options for cystinosis may include cysteamine – a cysteine-depleting agent, consuming lots of fluids and electrolytes to prevent excessive loss of water, medications to maintain a normal electrolyte balance, growth hormone therapy, insulin to manage insulin-dependent diabetes, testosterone to manage underactive testicular function, speech and language therapy, genetic counseling, avoiding bright lights, wearing sunglasses, keeping eyes lubricated, corneal transplant, and kidney transplantation.

What are the Similarities Between Cystinuria and Cystinosis?

• Cystinuria and cystinosis are two different hereditary conditions.
• Both of these conditions are genetic and involve the amino acid cysteine.
• They primarily affect the kidneys.
• They are autosomal recessive conditions.
• These can be treated through acid-specific medicines, lifestyle changes, and therapies.

What is the Difference Between Cystinuria and Cystinosis?

Cystinuria is an autosomal recessive condition that causes urine to become quickly supersaturated with cystine, which may precipitate out as pathognomonic hexagonally-shaped crystals, whereas cystinosis is an autosomal recessive disorder that causes cystine to accumulate in the lysosomes of proximal tubule cells. Thus, this is the key difference between cystinuria and cystinosis. Furthermore, cystinuria is due to mutations of two genes such as SLC3A1 and SLC7A9. On the other hand, cystinosis is due to mutations of the CTNS gene.

The infographic below presents the differences between cystinuria and cystinosis in tabular form for side-by-side comparison.

FAQ: Cystinuria and Cystinosis

What is the difference between cystine and cystine stones?

Cystine is an amino acid, while cystine stones refer to crystals or solid formations composed of accumulated cystine, often found in conditions like cystinuria.

What is cystinuria also known as?

Cystinuria is also known as renal calculi, nephrolithiasis, or urolithiasis.

What is the defect in cystinuria?

The defect in cystinuria involves impaired reabsorption of cystine in the kidneys, leading to its excessive excretion in the urine.

Summary – Cystinuria vs. Cystinosis

Cystinuria and cystinosis are two different hereditary conditions involving the amino acid cysteine, which follow an autosomal recessive inheritance pattern. However, cystinuria is an autosomal recessive condition that causes urine to become quickly supersaturated with cysteine,e which may precipitate out as pathognomonic hexagonally-shaped crystals, while cystinosis is an autosomal recessive disorder that causes cystine to accumulate in the lysosomes of proximal tubule cells. So, this summarizes the difference between cystinuria and cystinosis.

Reference:

1. “Cystinuria – An Overview.” ScienceDirect Topics.
2. “Cystinosis – Symptoms, Causes, Treatment.” National Organization for Rare Disorders.

Image Courtesy:

1. “Cystine crystals” By Sheri Terris (CC BY 2.0 DEED) via Flickr
2. “Cystinosis – kidney — intermed mag” By Nephron – Own work (CC BY-SA 3.0) via Commons Wikimedia