Mainzer-Saldino syndrome

What it is, symptoms and effects

From: MedlinePlus Genetics, National Library of Medicine

Mainzer-Saldino syndrome is a disorder characterized by kidney disease, eye problems, and skeletal abnormalities.

People with Mainzer-Saldino syndrome have chronic kidney disease that begins in childhood and gets worse over time. The rate at which the kidney disease worsens is variable, but the condition eventually leads to kidney failure in most affected individuals.

Degeneration of the light-sensitive tissue at the back of the eye (the retina) almost always occurs in this disorder, but the age at which this feature develops varies. Some affected individuals are blind or have severe vision impairment beginning in infancy, with the pattern of vision loss resembling a condition called Leber congenital amaurosis. In other people with Mainzer-Saldino syndrome, the retinal degeneration begins in childhood, but some vision is retained into early adulthood. The vision loss in these affected individuals resembles a category of retinal disorders called rod-cone dystrophies. The most common rod-cone dystrophy is called retinitis pigmentosa, and the vision problems in Mainzer-Saldino syndrome are sometimes referred to as such. However, the abnormal deposits of pigment in the retina from which retinitis pigmentosa gets its name are often not found in Mainzer-Saldino syndrome. As a result, some researchers use terms such as "atypical retinitis pigmentosa without pigment" to describe the retinal degeneration that occurs in Mainzer-Saldino syndrome.

The skeletal abnormality most characteristic of Mainzer-Saldino syndrome consists of cone-shaped ends of the bones (epiphyses) in the fingers (phalanges) that can be seen on x-ray images after the first year of life. Affected individuals may also have abnormalities of the thigh bones that occur in the epiphyses and adjacent areas where bone growth occurs (the metaphyses). Occasionally, other skeletal abnormalities occur, including short stature and premature fusion of certain skull bones (craniosynostosis) that affects the shape of the head and face. Affected individuals may also have a small rib cage, which sometimes causes breathing problems in infancy, but the breathing problems are usually mild.

A small number of individuals with this disorder have additional problems affecting other organs. These can include liver disease resulting in a buildup of scar tissue in the liver (hepatic fibrosis); cerebellar ataxia, which is difficulty with coordination and balance arising from problems with a part of the brain called the cerebellum; and mild intellectual disability.

Causes and biological mechanisms

From: MedlinePlus Genetics, National Library of Medicine

Mainzer-Saldino syndrome is usually caused by mutations in the IFT140 gene. This gene provides instructions for making a protein that is involved in the formation and maintenance of cilia, which are microscopic, finger-like projections that stick out from the surface of cells and participate in signaling pathways that transmit information within and between cells. Cilia are important for the structure and function of many types of cells, including cells in the kidneys, liver, and brain. Light-sensing cells (photoreceptors) in the retina also contain cilia, which are essential for normal vision. Cilia also play a role in the development of the bones, although the mechanism is not well understood.

The movement of substances within cilia and similar structures called flagella is known as intraflagellar transport (IFT). This process is essential for the assembly and maintenance of these cell structures. During intraflagellar transport, cells use molecules called IFT particles to carry materials to and from the tips of cilia. IFT particles are made of proteins produced from related genes that belong to the IFT gene family. Each IFT particle is made up of two groups of IFT proteins: complex A, which includes at least six proteins, and complex B, which includes at least 15 proteins. The protein produced from the IFT140 gene forms part of IFT complex A (IFT-A).

Mutations in the IFT140 gene that cause Mainzer-Saldino syndrome may change the shape of the IFT140 protein or affect its interactions with other IFT proteins, likely impairing the assembly of IFT-A and the development or maintenance of cilia. As a result, fewer cilia may be present or functional, affecting many organs and tissues in the body and resulting in the signs and symptoms of Mainzer-Saldino syndrome. Disorders such as Mainzer-Saldino syndrome that are caused by problems with cilia and involve bone abnormalities are called skeletal ciliopathies.

While IFT140 gene mutations are believed to account for most cases of Mainzer-Saldino syndrome, mutations in additional genes that have not been identified may also cause this disorder.

Inheritance and family implications

From: MedlinePlus Genetics, National Library of Medicine

This condition is inherited in an autosomal recessive pattern, which means both copies of the 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

Mainzer-Saldino syndrome is a rare disorder; its prevalence is unknown. At least 20 cases have been reported.

Which doctor should you see?

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

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

The material gathered for this draft does not provide a complete condition-specific treatment pathway for Mainzer-Saldino syndrome. That gap does not mean that treatment is unavailable. A clinician needs to establish the diagnosis and review current guidance before recommending medicines, procedures, rehabilitation or other support.

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.