Understanding Your Child's PIGT (MCAHS3) Diagnosis
At a Glance
PIGT-related MCAHS3 is a rare inherited disorder caused by changes in both copies of the PIGT gene. It can affect development, muscle tone, seizures, bones, eyes, and metabolism, and each child's symptoms and outlook can be different.
Receiving a diagnosis of PIGT-related Multiple Congenital Anomalies-Hypotonia-Seizures Syndrome 3 (or MCAHS3) often feels like entering a new and unfamiliar world. This name is a mouthful because it is a descriptive medical label: it tells you that a change in the PIGT gene is causing a variety of physical differences (congenital anomalies), low muscle tone (hypotonia), and seizures [1][2].
Because this condition is so rare, you may find that your child is the only person your local doctors have ever seen with this specific genetic change. This can feel isolating, but it is a reflection of the science, not your care. You have navigated a complex medical landscape to find an answer that a small number of published individuals worldwide have officially received in the medical literature [3][1].
Understanding the Syndrome
PIGT-CDG (the other common name for this condition) is a multi-system disorder, meaning it can affect several parts of the body at once. It belongs to a group called congenital disorders of glycosylation (CDG), specifically those affecting the GPI anchor [1][4]. Think of the GPI anchor like a specialized “hook” on the surface of a cell that holds important proteins in place. When the PIGT gene has a variation, the body cannot transfer these hooks correctly, and the proteins cannot do their jobs [5].
This “hook” problem can affect:
- The Brain: Most children experience global developmental delay and low muscle tone (hypotonia) [6]. Seizures are very common and can start as early as the first day of life or emerge during the first two years [6][7].
- The Skeleton: Some children are born with bone differences or are prone to fractures, though this varies significantly between individuals [8][9].
- The Eyes: Doctors often monitor for vision issues, including problems with the retina or the structure of the eye [10][5].
- Metabolism: A blood test for alkaline phosphatase (an enzyme) may show unusual levels—sometimes very low—which can be a clue for doctors investigating this syndrome [8][9].
Validating the “Diagnostic Odyssey”
If it took a variable or long time to get this answer, you are not alone. The journey to a rare diagnosis is often called a diagnostic odyssey. Many families face “false starts” where symptoms are initially mistaken for more common conditions, such as mitochondrial disease or other metabolic disorders [11][12]. Standard screening tests used for other disorders often come back normal in children with PIGT variants, which can lead to further delays and frustration for parents searching for answers [13][14].
Not Your Fault
One of the most important things to understand is that PIGT-CDG is an autosomal recessive genetic condition present from conception [7]. This means a child must inherit two changed copies of the gene—one from each parent—to be affected. Most parents are “carriers,” meaning they have one changed copy and one healthy copy, and they have no symptoms themselves. There is nothing you did, or did not do, that caused this to happen. It is not a result of parenting or pregnancy actions [15]. If both parents are confirmed carriers, there is generally a 25% recurrence risk in each pregnancy; a genetic counselor can discuss testing for relatives.
Living with Uncertainty
Because there are so few reported cases, there is no single “roadmap” for how a child’s condition will progress. The literature shows a wide range of experiences:
- Variable Severity: Some children have profound challenges and difficult-to-control seizures [6].
- Genotype-Phenotype Associations: Other children, particularly those with specific genetic variants (like the one known as p.Val528Met), have a reported association in a small number of individuals with more manageable seizures and moderate delays [7][1]. However, a genotype cannot reliably predict an individual child’s specific clinical course.
This variability means that while your child shares a diagnosis with others, their journey remains uniquely theirs.
The Emotional Weight of Rare Caregiving
Parents of children with ultra-rare conditions often describe a journey that is “strenuous and highly emotional” [16]. You are not just a parent; you have become a researcher, a care coordinator, and a fierce advocate. It is common to feel:
- Isolation: Because local doctors may not be familiar with the name MCAHS3, you may feel like the “expert” in the room, which is an exhausting role to play [17].
- Grief and Worry: It is natural to feel sadness about the challenges your child faces and uncertainty about what the future holds [18][19].
- Resilience: Research shows that connecting with other families—even those with similar but not identical “GPI-anchor” defects—can help build resilience and provide much-needed social support [20][16].
While the medical names are long and the community is small, you are now part of a global group of families and researchers working to better understand this rare chapter of human biology.
Common questions in this guide
What is PIGT-related MCAHS3?
What symptoms can a child with PIGT-CDG have?
How is PIGT-related MCAHS3 inherited, and could it happen again?
Can my child's PIGT variant predict how the condition will progress?
Why can it take so long to diagnose PIGT-related MCAHS3?
What support can help families caring for a child with MCAHS3?
Appointments are short. Make every minute count.
Specialist visits move fast. Let us help you prep so your time goes to what matters.
Understanding the condition
What does it mean for my child that this is a multi-system disorder?
About testing
Should my child have an alkaline phosphatase blood test, and what would it show?
Support for families
Where can I find other families who understand a rare diagnosis like this?
Get notified when new evidence is published on Intellectual disability-seizures-hypophosphatasia-ophthalmic-skeletal anomalies syndrome.
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References
References (20)
- 1
Case report: Functional analysis of the p.Arg507Trp variant of the PIGT gene supporting the moderate epilepsy phenotype of mutations in the C-terminal region.
Ben Ayed I, Jallouli O, Murakami Y, et al.
Frontiers in neurology 2023; (14()):1092887 doi:10.3389/fneur.2023.1092887.
PMID: 36970549 - 2
Analysis of exome data for 4293 trios suggests GPI-anchor biogenesis defects are a rare cause of developmental disorders.
Pagnamenta AT, Murakami Y, Taylor JM, et al.
European journal of human genetics : EJHG 2017; (25(6)):669-679 doi:10.1038/ejhg.2017.32.
PMID: 28327575 - 3
Spectrum of Multiple Congenital Anomalies-Hypotonia-Seizures Syndrome 3 (MCAHS3) Due to Phosphatidylinositol Glycan Biosynthesis Class T (PIGT) Gene Mutations: A Narrative Review.
Ranjan A, Alam MS, Kumar V, et al.
Cureus 2024; (16(5)):e60737 doi:10.7759/cureus.60737.
PMID: 38903302 - 4
Mutations in PIGS, Encoding a GPI Transamidase, Cause a Neurological Syndrome Ranging from Fetal Akinesia to Epileptic Encephalopathy.
Nguyen TTM, Murakami Y, Wigby KM, et al.
American journal of human genetics 2018; (103(4)):602-611 doi:10.1016/j.ajhg.2018.08.014.
PMID: 30269814 - 5
Expanding the clinical and molecular characteristics of PIGT-CDG, a disorder of glycosylphosphatidylinositol anchors.
Lam C, Golas GA, Davids M, et al.
Molecular genetics and metabolism 2015; (115(2-3)):128-140 doi:10.1016/j.ymgme.2015.04.007.
PMID: 25943031 - 6
PIGT-CDG, a disorder of the glycosylphosphatidylinositol anchor: description of 13 novel patients and expansion of the clinical characteristics.
Bayat A, Knaus A, Juul AW, et al.
Genetics in medicine : official journal of the American College of Medical Genetics 2019; (21(10)):2216-2223 doi:10.1038/s41436-019-0512-3.
PMID: 30976099 - 7
Deep-Phenotyping the Less Severe Spectrum of PIGT Deficiency and Linking the Gene to Myoclonic Atonic Seizures.
Bayat A, Pendziwiat M, Obersztyn E, et al.
Frontiers in genetics 2021; (12()):663643 doi:10.3389/fgene.2021.663643.
PMID: 34046058 - 8
A Novel Homozygous Missense Variant of PIGT Related to Multiple Congenital Anomalies-Hypotonia Seizures Syndrome 3 with Elevated of Serum ALP Level in a Thai Newborn Patient.
Klangjorhor J, Wiwattanadittakul N, Jaimalai T, et al.
International journal of molecular sciences 2025; (26(6)) doi:10.3390/ijms26062790.
PMID: 40141433 - 9
Compound Heterozygous PIGT Mutations in Multiple Congenital Anomalies-Hypotonia-Seizures Syndrome: First Case in Korea and Characterization by Persistent Hypophosphatasia.
Hur YJ, Lee BL, Chung WY, et al.
Annals of clinical and laboratory science 2021; (51(3)):422-425.
PMID: 34162574 - 10
Bilateral anterior segment dysgenesis and peripheral avascular retina with tractional retinal detachment in an infant with multiple congenital anomalies-hypotony-seizures syndrome 3.
Wu F, Goldenberg PC, Mukai S
Ophthalmic genetics 2021; (42(3)):334-337 doi:10.1080/13816810.2021.1888133.
PMID: 33620284 - 11
Novel PGM1 Mutation in Congenital Disorder of Glycosylation Type 1T: A Case Report of Liver Failure and Myopathy.
Al-Ahmari AA
The American journal of case reports 2025; (26()):e948797 doi:10.12659/AJCR.948797.
PMID: 41182978 - 12
CCDC115-CDG: A new rare and misleading inherited cause of liver disease.
Girard M, Poujois A, Fabre M, et al.
Molecular genetics and metabolism 2018; (124(3)):228-235 doi:10.1016/j.ymgme.2018.05.002.
PMID: 29759592 - 13
The challenge of CDG diagnosis.
Francisco R, Marques-da-Silva D, Brasil S, et al.
Molecular genetics and metabolism 2019; (126(1)):1-5 doi:10.1016/j.ymgme.2018.11.003.
PMID: 30454869 - 14
Multisystemic Clues and Diagnostic Gaps: A Comparative Analysis of Pediatric Congenital Disorders of Glycosylation Patients.
Gokalp S, Akar HT, Aktasoglu EO, et al.
Pediatric neurology 2026; (185()):89-94 doi:10.1016/j.pediatrneurol.2026.09.015.
PMID: 42854636 - 15
Carer burden in rare inherited diseases: a literature review and conceptual model.
Sandilands K, Williams A, Rylands AJ
Orphanet journal of rare diseases 2022; (17(1)):428 doi:10.1186/s13023-022-02561-w.
PMID: 36494728 - 16
Experiences of parents with children with congenital disorders of glycosylation: What can we learn from them?
Cardão C, Barros L, Francisco R, et al.
Disability and health journal 2021; (14(3)):101065 doi:10.1016/j.dhjo.2021.101065.
PMID: 33531289 - 17
Current challenges and opportunities in the care of patients with fibrodysplasia ossificans progressiva (FOP): an international, multi-stakeholder perspective.
Pignolo RJ, Bedford-Gay C, Cali A, et al.
Orphanet journal of rare diseases 2022; (17(1)):168 doi:10.1186/s13023-022-02224-w.
PMID: 35436894 - 18
Understanding the Experiences and Needs of Parents With Children With Epidermolysis Bullosa. A Qualitative Study to Inform the Development of a Self-help Toolkit.
Hughes O, Martin F, Thompson AR
The British journal of dermatology 2026; doi:10.1093/bjd/ljag477.
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Children with a rare congenital genetic disorder: a systematic review of parent experiences.
von der Lippe C, Neteland I, Feragen KB
Orphanet journal of rare diseases 2022; (17(1)):375 doi:10.1186/s13023-022-02525-0.
PMID: 36253830 - 20
Resilience in patients and family caregivers living with congenital disorders of glycosylation (CDG): a quantitative study using the brief resilience coping scale (BRCS).
Poejo J, Gomes AI, Granjo P, Dos Reis Ferreira V
Orphanet journal of rare diseases 2024; (19(1)):98 doi:10.1186/s13023-024-03043-x.
PMID: 38439013
This page provides general information about PIGT-related MCAHS3 for educational purposes and does not replace medical advice. Your child's genetics, neurology, and other specialists can interpret the diagnosis and plan care for your child's specific needs.