Maffucci syndrome is a rare, non-inherited disorder in which benign cartilage tumors called enchondromas develop alongside abnormal blood vessel growths, primarily in the hands and long bones. It affects fewer than 1 in 100,000 people, appears in early childhood, and carries a significant cancer risk that sets it apart from many other skeletal conditions. The underlying cause, traced to random mutations in specific metabolic enzymes during embryonic development, has only been understood since 2011, and that discovery has recently opened the door to the first targeted treatments.
What Defines Maffucci Syndrome
Two features must be present for a diagnosis: multiple enchondromas and vascular anomalies. Enchondromas are clusters of cartilage that form inside bones where they shouldn’t be, expanding the bone from within and distorting its shape. In Maffucci syndrome, there are typically more than three of these growths, and they tend to appear in the small bones of the hands and feet as well as the long bones of the arms and legs. The vascular component usually takes the form of venous malformations (historically called hemangiomas), which are tangles of abnormal veins that create soft, bluish, compressible lumps under the skin or deeper in tissue.
The enchondromas and vascular lesions can occur virtually anywhere in the body, but the hands are the most common location. Long bone involvement is also typical and tends to cause progressive skeletal deformity and pathological fractures, meaning bones break under normal stress because the tumor has weakened them from inside.
Symptoms usually first appear around age four, and the condition affects males and females equally with no racial predisposition.
Why It Happens
Maffucci syndrome is not something you inherit from your parents. It arises from somatic mutations, meaning genetic changes that occur spontaneously in a subset of cells during early development. A landmark genetics study found that about 77% of Maffucci syndrome patients carried mutations in the IDH1 or IDH2 genes within their tumors, with IDH1 mutations accounting for the vast majority of cases. These same mutations were not found in the patients’ blood, confirming that the changes exist only in the affected tissues, a pattern called somatic mosaicism.
IDH1 and IDH2 encode enzymes involved in cellular metabolism. Normally, these enzymes help convert one molecule into another as part of the cell’s energy cycle. When mutated, however, they gain an abnormal new function: instead of producing the normal metabolic product, they churn out high levels of a substance called D-2-hydroxyglutarate. In healthy cells, this substance exists at very low levels and is tightly regulated. When it accumulates, it disrupts the chemical signals that tell stem cells what type of tissue to become. Specifically, research has shown that D-2-hydroxyglutarate blocks the normal process by which mesenchymal stem cells mature into bone and instead pushes them toward becoming cartilage. That shift during skeletal development provides a plausible explanation for why enchondromas form in the first place.
The timing matters. Because the mutation occurs in a developing embryo, only cells descended from the originally affected cell carry the error. This is why Maffucci syndrome affects certain regions of the body while leaving others untouched, and why no two patients look exactly alike.
How It Differs from Ollier Disease
Ollier disease is the closest relative of Maffucci syndrome, and the two are sometimes discussed as a spectrum. Both are characterized by multiple enchondromas and share the same IDH1/IDH2 mutation pathway. The critical distinction is that Ollier disease involves enchondromas alone, while Maffucci syndrome adds the vascular component.
There are other differences in how the two conditions typically present. Ollier disease enchondromas tend to cluster on one side of the body, with a strong preference for the arms and legs. In Maffucci syndrome, the enchondromas are more often distributed on both sides. Both conditions cause overlapping complications: joint swelling, deformity around joints, limited mobility, scoliosis, bone shortening, leg-length discrepancy, gait problems, pain, and pathological fractures. Patients with either disorder face a roughly 50% lifetime risk of developing a malignancy such as chondrosarcoma, glioma, or ovarian juvenile granulosa cell tumor. The vascular growths in Maffucci syndrome add an additional layer of concern, as they themselves become malignant in about 8.5% of cases.
Skeletal Complications and Growth
The skeletal impact of Maffucci syndrome goes well beyond the enchondromas themselves. As a child grows, the enchondromas sitting near growth plates interfere with normal bone elongation. Bone grows in length, but the cartilage tumor lags behind and expands unevenly, pulling the bone into angular deformities. One well-documented case involved a 12-year-old girl whose enchondromas in her left knee area caused a progressive knock-knee deformity severe enough to require surgical correction.
Limb-length discrepancy is common and can be dramatic. In one reported case, a patient had 8 cm of shortening in the thighbone and an additional 3.5 cm in the shinbone on the affected side, for a total difference of over 11 cm between legs. Imaging in that case revealed multiple well-defined lesions throughout the femur, tibia, and fibula, concentrated in the areas where the shaft meets the wider ends of the bone. Corrective surgery involving both deformity straightening and gradual bone lengthening was used to restore more normal alignment and leg length.
Pathological fractures remain a persistent risk throughout life. The enchondromas weaken bone structurally, so a stumble or minor fall that would be harmless for most people can snap a bone riddled with cartilage tumors. The hands, being the most commonly affected site, are especially vulnerable, and repeated fractures there can progressively reduce grip strength and fine motor ability.
Cancer Risk and Surveillance
The most serious long-term concern for anyone with Maffucci syndrome is malignant transformation. Estimates of the overall malignancy rate are high: one literature review placed it between 52% and 57% over a lifetime, while survey-based research put it around 50%. These numbers are far above the general population’s cancer risk and make lifelong monitoring essential.
Chondrosarcoma, a cancer of cartilage, is the most common malignancy, accounting for roughly 30% of the malignant lesions seen in Maffucci syndrome. The average age at which an enchondroma transforms into chondrosarcoma is around 40. Warning signs include a previously stable lump that starts growing rapidly, new or worsening pain at the site of a known enchondroma, or imaging changes showing the tumor eroding through the outer bone surface. Whole-exon genetic analysis in at least one chondrosarcoma case confirmed the presence of an IDH1 R132C mutation in the cancerous tissue but not in the patient’s blood, reinforcing that the same somatic mutation driving the benign enchondromas also underlies the malignant transformation.
Beyond chondrosarcoma, there is also an elevated risk for cancers that have nothing to do with cartilage. Brain tumors (gliomas), ovarian tumors (particularly juvenile granulosa cell tumors), and other sarcomas have all been reported at higher-than-expected rates. The vascular lesions themselves can rarely transform into hemangiosarcomas or hemangioendotheliomas.
Because the cancer risk is so broad and the transformations can happen over decades, the standard approach is long-term oncologic surveillance. This typically means regular imaging of known enchondromas to watch for changes in size or character, periodic screening for other malignancies, and a low threshold for biopsy when something looks different. There is no universally agreed-upon screening schedule, partly because the condition is so rare that large clinical trials have never been feasible. Most guidance comes from case series and expert consensus.
Managing the Vascular Component
The venous malformations in Maffucci syndrome are not just cosmetic. They can compress nearby structures, cause pain, interfere with function, and occasionally bleed. In the extremities, they may contribute to limb asymmetry alongside the skeletal deformities. When venous malformations occur in the head and neck region, they can obstruct the airway or affect swallowing.
Treatment depends on location and severity. In one reported case of extensive venous malformations in the mouth, throat, and face, a combination approach was used: sclerotherapy (injecting a substance to shrink the malformation) tackled the deeper oropharyngeal lesions, while surgical excision removed the oral cavity and facial skin lesions. Post-treatment imaging showed the oral malformations were nearly eliminated and the oropharyngeal ones had stabilized, with normal facial appearance and function restored. This kind of combined approach reflects the broader principle in vascular malformation management: no single technique works for every lesion, and treatment is tailored to the anatomy and the specific complications caused.
For less severe or asymptomatic venous malformations, observation may be all that’s needed, especially when they are small, stable, and not causing functional problems.
When the Diagnosis Gets Tricky
Maffucci syndrome sits within a larger family of vascular anomaly syndromes. In the classification system used by the International Society for the Study of Vascular Anomalies (ISSVA), it is grouped alongside conditions like Klippel-Trenaunay syndrome, Proteus syndrome, and CLOVES syndrome, all of which involve vascular malformations combined with other anomalies such as tissue overgrowth or skeletal changes. A child presenting with a limb that is longer or larger than the other, with visible vascular lesions, could plausibly have any of several conditions on this list, and the specific combination of enchondromas plus venous malformations is what pins down Maffucci syndrome.
The distinction from Ollier disease is the most commonly needed one. If a patient has multiple enchondromas but no vascular lesions at all, the diagnosis is Ollier disease. Once vascular growths appear alongside the enchondromas, the classification shifts to Maffucci syndrome. Occasionally the vascular component is subtle or develops later than the enchondromas, so a patient initially diagnosed with Ollier disease may be reclassified if vascular lesions emerge over time.
Solitary enchondromas are common in the general population and nearly always harmless. The key difference is multiplicity: more than three enchondromas, especially with a particular anatomic pattern, raises the suspicion of a syndromic condition rather than isolated incidental findings.
Emerging Targeted Treatments
For most of its medical history, Maffucci syndrome has been managed reactively: surgeons correct deformities, repair fractures, excise or shrink vascular malformations, and remove enchondromas that threaten to become cancerous. There has been no drug that treats the underlying disease process. That may be changing.
The discovery that IDH1 mutations drive enchondroma formation created a logical therapeutic target. IDH inhibitors were originally developed for cancers like acute myeloid leukemia and certain brain tumors that carry the same IDH mutations. Ivosidenib, a drug that specifically blocks mutant IDH1, has now been tried in at least one Maffucci syndrome patient. A 2024 case report documented both clinical and radiological improvement of enchondromas in response to ivosidenib treatment, offering the first evidence that the enchondromas themselves might be medically treatable rather than requiring surgery alone.
This is very early evidence, a single case report. But the biological rationale is strong: the same mutation that drives the tumors in leukemia is driving the enchondromas here, and the drug that blocks it in leukemia appears to block it in bone as well. The authors of that report emphasized the urgent need for clinical trials to evaluate the long-term benefits and risks of IDH inhibitors in these rare bone diseases. Given how few patients exist worldwide, organizing those trials will be a challenge, but the molecular logic and the preliminary result are encouraging.
Living with a Condition That Has No Cure
Because Maffucci syndrome results from mutations scattered through tissues during embryonic development, there is no way to reverse or eliminate the underlying genetic cause. Management is a lifelong process of monitoring, intervening when complications arise, and planning ahead. Orthopedic care often dominates childhood and adolescence, when growth-plate disruption is actively causing deformities and limb-length differences. Many patients undergo multiple surgeries before adulthood.
The psychological burden is worth acknowledging. Visible hand deformities, repeated surgeries, limb asymmetry, and the knowledge of elevated cancer risk all take a toll. Support from multidisciplinary teams that include not just orthopedic surgeons and oncologists but also psychologists, physical therapists, and genetic counselors can make a real difference in quality of life. Because the condition is not hereditary, patients can be reassured that they are unlikely to pass it on to their children, which is often one of the first questions families ask after diagnosis.
The rarity of the syndrome means that most physicians will never see a case in their careers. Patients and families frequently find that they know more about the condition than their local doctors do. Connecting with specialized centers that have experience with enchondromatosis and vascular malformation syndromes can improve both the quality of surgical care and the appropriateness of cancer surveillance strategies.
Monomelic Presentations and Other Unusual Patterns
While the textbook description of Maffucci syndrome involves bilateral enchondromas scattered across multiple limbs, the condition does not always present that way. Monomelic Maffucci syndrome, where all the enchondromas and vascular lesions are confined to a single limb, has been documented. In one case, a 12-year-old girl had enchondromas and venous malformations confined entirely to her left leg, with her right leg and the rest of her skeleton unaffected. This pattern makes sense given the somatic mosaic origin: if the mutation occurred in a cell whose descendants populated only one limb bud, only that limb would be affected.
Unusual locations have also been reported. Although the hands and long bones are the classic sites, enchondromas and vascular malformations can appear in the pelvis, ribs, skull, and spine. The clinical significance varies by location. Spinal involvement can threaten the spinal cord. Pelvic enchondromas are harder to monitor for malignant transformation because changes in size are less obvious than in a finger. Head and neck vascular malformations, as described earlier, can threaten airway patency. These atypical presentations underscore why imaging of the whole skeleton is typically recommended at diagnosis, even if the initial complaint involves only one limb.