A Note Before You Read

I am 71 years old, and I have lived with Klippel-Trenaunay Syndrome from the moment I was born — though no one knew to call it that until I was 42.

What follows is not a medical textbook, and I am not a physician. I am a patient. A husband, a father, a person of faith. Someone who spent the first four decades of his life without a name for what was happening inside his body, and who has spent the three decades since learning everything he could — not to become an expert, but to survive well, and to help others do the same.

I was diagnosed at 42 by a Chief Vascular Surgeon at Scripps Medical Clinic in California — a physician experienced enough with KTS to recognize what so many before him had missed. By then, the damage was done. Permanent. Disabling. I was declared permanently disabled that same year. I do not say this to invite pity. I say it because the gap between birth and diagnosis is not merely a personal wound — it is a pattern. It happens to others. It may be happening to the person holding this page right now.

I have since had surgical intervention at the Gonda Vascular Center at Mayo Clinic in Rochester, Minnesota, under a multidisciplinary team of KTS pioneers. I have attended joint medical conferences. I have read deeply in NIH and medical science literature. I have walked alongside others in support groups as both a fellow patient and a mentor. None of this makes me a doctor. All of it makes me a witness.

I share this material with every new physician I see — specialist or general practitioner — because the honest truth is that most doctors have not encountered KTS, and fewer still understand its full complexity. I do not say this with bitterness. I say it because it is simply true, and because naming it honestly is the first step toward the kind of partnership that good care requires.

If you are a patient or a parent, I hope this helps you feel less alone, and better equipped for the conversations ahead.

If you are a physician, I offer this not as a challenge to your knowledge, but as a bridge. You bring the clinical training. I bring thirty years of living inside this condition. Together, we can do better than either of us could alone.

Please read what follows with that spirit in mind. And whatever you do — whatever any of us do — please work with a qualified medical team. This is not a condition to navigate alone, and nothing I have written here replaces the care of physicians who know it well.

Understanding PROS and Klippel-Trenaunay Syndrome

What Is PROS?

PROS — PIK3CA-Related Overgrowth Spectrum — is an umbrella term for a group of rare congenital conditions that share a common genetic root: a mutation in the PIK3CA gene. In plain terms, think of this gene as the body’s volume knob for cell growth. It helps produce an enzyme that signals cells when to grow, multiply, and move. In PROS, that knob gets turned up too high — but only in some cells, not the whole body. This is called a somatic or mosaic mutation, meaning it arises early in fetal development and affects only certain patches of tissue.

The result can range from something as small as an enlarged finger to more extensive involvement across an entire limb or side of the body — affecting skin, fat, muscle, bone, blood vessels, lymphatic tissue, or even the brain. Before genetic testing made this shared cause visible, each variation was treated as a separate syndrome. They are now grouped under PROS because they share the same underlying driver.

Conditions within the PROS family include:

• CLOVES syndrome — congenital fatty masses, vascular birthmarks, skin changes, and spinal involvement
• MCAP — brain overgrowth, capillary skin stains, and often developmental delays or seizures
• Klippel-Trenaunay Syndrome (KTS) — described in detail below
• Others, including isolated enlarged digits, hemihyperplasia, and lymphatic malformations

Common threads across PROS conditions include port-wine stains, abnormal veins or lymphatic swelling, fatty overgrowth, and bone or soft tissue enlargement — along with the complications these bring: pain, limited mobility, blood clots, and bleeding.

Klippel-Trenaunay Syndrome

KTS is a congenital vascular malformation disorder — meaning it is present from birth and involves abnormal development of the blood and lymphatic vessels. It is not a single defect but a pattern of combined anomalies, classically described as a triad of three features:

• A port-wine stain (capillary malformation)
• Abnormal veins or lymphatic malformations — varicosities, swelling, or unusual vessel structures
• Soft tissue and/or bone overgrowth — often making one limb noticeably larger, longer, or wider than the other

It is worth knowing that the physicians who first described this condition in 1900 — French doctors Maurice Klippel and Paul Trenaunay — did not require all three features to be present. Their original term, roughly translated, was “varicose nevus with bone overgrowth.” Today, diagnosis is typically made when any two of the three classic signs are present, in any combination. This flexibility reflects something important: KTS does not look the same in every person. The disruption happens early in fetal development, and where and when it occurs shapes everything that follows.

When a PIK3CA mutation is identified in affected tissue, KTS is now classified under the broader PROS umbrella. But not every KTS diagnosis comes with genetic confirmation — low-level mosaicism and testing limitations can make the mutation difficult to detect. KTS can and does remain a clinical diagnosis, based on symptoms and imaging. The label has persisted for good reason: it describes a specific, recognizable pattern centered on the limbs, involving slow-flow vascular malformations (capillary, venous, and lymphatic), without the high-flow arteriovenous shunts seen in related conditions.

How KTS Is Classified Today

The International Society for the Study of Vascular Anomalies (ISSVA) provides the current standard framework for classifying congenital vascular conditions, most recently updated in 2025. Within that framework, KTS falls under slow-flow combined vascular malformations — often designated CLVM (capillary-lymphatic-venous malformation) with hypertrophy when overgrowth is present.

This classification matters because it guides treatment. And critically, it is built on more than visual observation. Comprehensive imaging — MRI, MR angiography, CT, and Doppler ultrasound — is essential for understanding flow characteristics, lesion depth, and the full extent of involvement. Diagnosing by appearance alone is no longer considered an acceptable practice. The stakes of a missed or mistaken diagnosis are too high.

Conditions That Are Frequently Mistaken for KTS

Several conditions share enough surface features with KTS — port-wine stains, limb swelling, vascular birthmarks — that misdiagnosis was common before advanced imaging and genetic testing became standard. It’s important to distinguish these from Parkes Weber Syndrome, which can look strikingly similar but involves high-flow arteriovenous malformations. This distinction matters enormously: Parkes Weber carries different risks (including heart failure) and requires different treatment, including embolization. It is typically linked to mutations in the RASA1 gene, not PIK3CA.

Other conditions that can be confused with KTS include Proteus syndrome (AKT1-related, with more severe and distorting features) and mixed PROS presentations. Accurate differentiation — through ISSVA-aligned imaging and targeted genetic testing — is not a formality. It directly determines whether the care a patient receives is appropriate or potentially harmful.

A Word on Treatment

Management of KTS is multidisciplinary by necessity. No single specialist owns this condition, and no single treatment addresses it. Depending on the individual’s presentation, care may include compression therapy, sclerotherapy, surgical intervention, and — for confirmed PIK3CA cases — targeted medical therapy such as alpelisib. The right path requires the right diagnosis first, and the right diagnosis requires physicians willing to look carefully, consult broadly, and take the patient’s full picture seriously.