Annual prevalence estimation of lymphatic malformation with a cutaneous component: observational study of a national representative sample of physicians.

Background: Lymphatic malformations (LMs) represent a potentially life-threatening, rare disease of the lymphatic system characterized by development of abnormal vessels, outpouchings, or cysts filled with lymphatic fluid. There are three morphologic types of LMs based on the size of the individual cysts: macrocystic (typically > 2 cm), microcystic (generally < 2 cm), and mixed (includes aspects of both). Macrocystic LMs typically exist beneath the skin and often can involve vascular components and/or organs. Microcystic LMs often have a cutaneous component and clinically present with lymphorrhea, bleeding, pain, itching, malodor, and functional deficits. There are no treatments approved by the US Food and Drug Administration (FDA) for either macrocystic or microcystic lymphatic malformations. The totality of the epidemiologic literature for LM is limited to the incidence of the disease among various birth cohorts. This is the first nationally representative study to estimate the national managed prevalence for patients with microcystic LM or combined LM with a cutaneous component annually across physician specialties likely to manage this condition. We conducted a retrospective observational survey of a nationally representative sample of patient-care physicians in the United States most likely to manage lymphatic malformations with a cutaneous component (LMC). Once recruited, target physicians participated via an electronic questionnaire. We weighted study physician self-estimates of the number of LMC patients treated in the past 12 months to reflect the specialists' corresponding proportion in the national universe. All patient information was anonymous; no personally identifiable information was collected.

Results: Of the 420 physicians who visited the study website, 316 agreed to be screened and to participate (75.2% participation rate). Our survey results indicated the estimated number of unique annually managed LMC patients by target specialists is 79,920 (CI 66,600-93,250). This number corresponds to managed prevalence of 24.1 LMC patients per 100,000 population (CI 19.6/100,000-28.4/100,000).

Conclusions: The study indicates that while rare, LMC affects a substantial number of people in the US (79,920) who are being managed by one or more specialists. By better understanding the prevalence of people living with LMC who require treatment, efforts to both increase disease awareness and to identify underserved populations in need of potential new treatments can be better focused.