Update and audit of the St George's classification algorithm of primary lymphatic anomalies: a clinical and molecular approach to diagnosis

Abstract

Primary lymphatic anomalies may present in a myriad of ways and are highly heterogenous. Careful consideration of the presentation can lead to an accurate clinical and/or molecular diagnosis which will assist with management. The most common presentation is lymphoedema, swelling resulting from failure of the peripheral lymphatic system. However, there may be internal lymphatic dysfunction, for example, chylous reflux, or lymphatic malformations, including the thorax or abdomen. A number of causal germline or postzygotic gene mutations have been discovered. Some through careful phenotyping and categorisation of the patients based on the St George's classification pathway/algorithm. The St George's classification algorithm is aimed at providing an accurate diagnosis for patients with lymphoedema based on age of onset, areas affected by swelling and associated clinical features. This has enabled the identification of new causative genes. This update brings the classification of primary lymphatic disorders in line with the International Society for the Study of Vascular Anomalies 2018 classification for vascular anomalies. The St George's algorithm considers combined vascular malformations and primary lymphatic anomalies. It divides the types of primary lymphatic anomalies into lymphatic malformations and primary lymphoedema. It further divides the primary lymphoedema into syndromic, generalised lymphatic dysplasia with internal/systemic involvement, congenital-onset lymphoedema and late-onset lymphoedema. An audit and update of the algorithm has revealed where new genes have been discovered and that a molecular diagnosis was possible in 26% of all patients overall and 41% of those tested.

Keywords: central conducting lymphatic anomaly (CCLA); generalised lymphatic anomalies (GLA); lymphatic; primary lymphoedema.

Figure 1

St George’s classification algorithm for primary lymphatic anomalies. The five main groupings (colour coded) with their various clinical subtypes of disease. Primary lymphoedema is the major clinical feature in the green, pink and purple sections. Text in red indicates the suggested genetic test and/or differential diagnosis for the subgroup, however, the indicated genes do not explain the cause of disease in all patients in each grouping. For example, only 70% of patients with Milroy disease are explained by mutations in FLT4/VEGFR3. FH, family history; +ve, positive; −ve, negative. (Image shared by St George’s Lymphovascular Research Group under the CC BY-SA 4.0 International licence on Wikimedia Commons).

Figure 2

A graphic representation of the 227 audited patients seen in clinic in 2016 and their distribution across the five categories from figure 1 (pie chart). (A–G) Images show features of each category. (A) Patients with postzygotic mutations often present with asymmetrical swelling and segmental overgrowth as this patient, who is mosaic for a mutation in KRAS. (B) Webbed neck in Noonan syndrome. (C) In rare cases, swellings can be widespread affecting all segments of the body such as in this child with biallelic CCBE1 mutations. (D) In milder forms, often just the dorsum of the foot is affected as in this baby with a VEGFR3 mutation. (E, F) Lower limb swelling and distichiasis (arrowheads in F) in a patient with a FOXC2 mutation. (G) Lymphoedema is a major cause of skin disease and affected patients suffer from severe and recurrent episodes of cutaneous infection, especially HPV-associated warts as seen in patients with GATA2 mutations. GLD, generalised lymphatic dysplasia.