Renal tubular dysgenesis

What it is, symptoms and effects

From: MedlinePlus Genetics, National Library of Medicine

Renal tubular dysgenesis is a severe kidney disorder characterized by abnormal development of the kidneys before birth. In particular, kidney structures called proximal tubules are absent or underdeveloped. These structures help to reabsorb needed nutrients, water, and other materials into the blood and excrete everything else into the urine. Without functional proximal tubules, the kidneys cannot produce urine (a condition called anuria).

Fetal urine is the major component of the fluid that surrounds the fetus (amniotic fluid), and anuria leads to decreased amniotic fluid levels (oligohydramnios). Amniotic fluid helps cushion and protect the fetus and plays a role in the development of many organs, including the lungs. Oligohydramnios causes a set of abnormalities called the Potter sequence, which includes distinctive facial features such as a flattened nose and large, low-set ears; excess skin; inward- and upward-turning feet (clubfeet); and underdeveloped lungs.

Renal tubular dysgenesis also causes severe low blood pressure (hypotension). In addition, bone development in the skull is abnormal in some affected individuals, causing a large space between the bones of the skull (fontanelles).

As a result of the serious health problems caused by renal tubular dysgenesis, affected individuals usually die before birth, are stillborn, or die soon after birth from respiratory failure. Rarely, with treatment, affected individuals survive into childhood. Their blood pressure usually normalizes, but they quickly develop chronic kidney disease, which is characterized by reduced kidney function that worsens over time.

Causes and biological mechanisms

From: MedlinePlus Genetics, National Library of Medicine

Mutations in the ACE, AGT, AGTR1, or REN gene can cause renal tubular dysgenesis. These genes are involved in the renin-angiotensin system, which regulates blood pressure and the balance of fluids and salts in the body and plays a role in kidney development before birth.

The renin-angiotensin system consists of several proteins that are involved in a series of steps to produce a protein called angiotensin II. In the first step, the renin protein (produced from the REN gene) converts a protein called angiotensinogen (produced from the AGT gene) to angiotensin I. In the next step, angiotensin-converting enzyme (produced from the ACE gene) converts angiotensin I to angiotensin II. Angiotensin II attaches (binds) to the angiotensin II receptor type 1 (AT1 receptor; produced from the AGTR1 gene), stimulating chemical signaling.

By binding to the AT1 receptor, angiotensin II causes blood vessels to narrow (constrict), which results in increased blood pressure. This protein also stimulates production of the hormone aldosterone, which triggers the absorption of salt and water by the kidneys. The increased amount of fluid in the body also increases blood pressure. Proper blood pressure, which delivers oxygen to the developing tissues during fetal growth, is required for normal development of the kidneys (particularly of the proximal tubules) and other tissues.

Mutations in the ACE, AGT, AGTR1, or REN gene impair the production or function of angiotensin II, leading to a nonfunctional renin-angiotensin system. Without this system, the kidneys cannot control blood pressure. Because of low blood pressure, the flow of blood is reduced (hypoperfusion), and the fetal tissues do not get enough oxygen during development. As a result, kidney development is impaired, leading to the features of renal tubular dysgenesis. Hypoperfusion also causes the skull abnormalities found in individuals with this condition.

Medications that block the activity of the angiotensin-converting enzyme or the AT1 receptor are used to treat high blood pressure. Because these drugs impair the renin-angiotensin system, they can cause an acquired (non-inherited) form of renal tubular dysgenesis in fetuses of pregnant women who take them. Acquired renal tubular dysgenesis can also result from other conditions that cause renal hypoperfusion during fetal development. These include heart problems, congenital hemochromatosis, and a complication that can occur in twin pregnancies called twin-to-twin transfusion syndrome.

Inheritance and family implications

From: MedlinePlus Genetics, National Library of Medicine

Renal tubular dysgenesis is inherited in an autosomal recessive pattern, which means both copies of the affected gene in each cell have mutations. The parents of an individual with an autosomal recessive condition each carry one copy of the mutated gene, but they typically do not show signs and symptoms of the condition.

How common is it?

From: MedlinePlus Genetics, National Library of Medicine

Renal tubular dysgenesis is a rare disorder, but its prevalence is unknown.

Reported clinical features and what the terms mean

The following findings are associated with this condition in Orphanet. They are not a checklist for diagnosing yourself, and they do not all occur in every affected person. Some are examination, imaging or laboratory findings that cannot be recognised at home.

The frequency labels describe how often a finding was reported among people with the condition in the source. They do not give the chance that a person with that symptom has the condition. Definitions below reproduce HPO terminology; they explain the term, not the likely severity in an individual.

Hypertelorism · Very frequent (99-80%)

Interpupillary distance more than 2 SD above the mean (alternatively, the appearance of an increased interpupillary distance or widely spaced eyes).

Joint hypermobility · Very frequent (99-80%)

The capability that a joint (or a group of joints) has to move, passively and/or actively, beyond normal limits along physiological axes.

Multiple renal cysts · Very frequent (99-80%)

The presence of many cysts in the kidney.

Polyhydramnios · Very frequent (99-80%)

The presence of excess amniotic fluid in the uterus during pregnancy.

Premature birth · Very frequent (99-80%)

The birth of a baby of less than 37 weeks of gestational age.

Proximal tubulopathy · Very frequent (99-80%)

Dysfunction of the proximal tubule, which is the portion of the duct system of the nephron of the kidney which leads from Bowman's capsule to the loop of Henle.

Renotubular dysgenesis · Very frequent (99-80%)

A developmental defect characterized by absence or poor development of proximal renal tubules.

Pulmonary hypoplasia · Very frequent (99-80%)

Other findings in the same source

From: Orphanet

Additional reported features include Bilateral single transverse palmar creases (Occasional (29-5%)); Microcephaly (Occasional (29-5%)); Nephropathy (Occasional (29-5%)); Oligohydramnios (Occasional (29-5%)); Tetralogy of Fallot (Occasional (29-5%)). This is a selected summary, not a complete description of the condition.

Which doctor should you see?

The suggested department for discussing Renal tubular dysgenesis is Clinical Genetics, with a clinical geneticist as the relevant type of clinician. Paediatrician (children) or physician (adults), with clinical geneticist referral.

Additional services that may be relevant, depending on the findings, include: Nephrology.

This is an editorial referral starting point. The appropriate clinic depends on the person’s age, symptoms, previous diagnosis and local services. The first clinician can decide whether another specialty or a team is needed; a department label does not confirm the diagnosis.

How to prepare for an assessment

Bring a short timeline of the main symptoms: when they first appeared, whether they are constant or episodic, what seems to change them, and how they affect daily activities. Include previous reports, discharge summaries, current medicines and supplements, allergies, and any relevant family history. A dated record is more useful than trying to match every feature in an online article.

Ask the clinician what is already established and what remains uncertain. If a test is suggested, ask what question it answers, what its limitations are and how the result would change the next step. The information here is not an instruction to arrange every possible test. In children, bring growth, developmental and school information if it is relevant to the concern.

• Does the exact genetic or chromosome finding explain the observed features?
• Would a genetic counsellor help the family understand the result?
• Which organ-specific assessments are appropriate for this particular diagnosis?

Treatment discussions and follow-up

Where the source describes treatments, these are an overview of possible care, not a prescription for an individual. Ask which option applies to the confirmed diagnosis, what benefit is expected, what adverse effects to watch for and how progress will be assessed. Availability, approvals and local practice can differ from the country described in the source.

Before leaving the appointment, clarify the next review date, who will communicate results, and whom to contact if the situation changes. Discuss difficulties with sleep, work, school, mobility, eating or emotional wellbeing when these are relevant. Practical support may require coordination between the treating clinician and other services.

The collected references do not establish a complete prevention or long-term outlook section for this entry. Missing information should not be interpreted as proof that prevention is impossible or that a particular outcome is inevitable. Ask what is known for the exact subtype, stage and personal circumstances, and which uncertainties remain.

When to seek emergency help

Severe breathing difficulty, collapse, new stroke-like symptoms, a seizure that is prolonged or repeated without recovery, uncontrolled major bleeding, or an immediate risk of self-harm require emergency help. In India, call 112 or reach the nearest emergency department. This is a general, non-exhaustive warning list; it is not a condition-specific triage tool.