Clinical characteristics of patients
Of the 27 patients included in the study, 18 were female and 9 were male. Their mean age was 35 years (range, 1 to 77 years), whereas their average body mass index was 24.8. Notable past medical histories of patients included ongoing lung cancer (n = 1), hypertension (n = 4), and diabetes mellitus (n = 2). Three patients had familial history of primary lymphedema in second-degree relatives. In one of these cases, both the proband and her mother harbored a pathological variant of CELSR1 (see Case presentation).
In 41% of the patients (n = 11), symptoms first appeared between the ages of 20 and 40 years. In contrast, the rate of onset of symptoms before age 10 was 15% (n = 4), that between the ages of 10 and 20 years was 15% (n = 4), and that after age 40 was 26% (n = 7). The most common lymphedema location was unilateral lower extremity (n = 18, 67%), followed by bilateral lower extremity (n = 4, 15%), unilateral upper extremity (n = 3, 11%), bilateral upper extremity (n = 2, 7%), and the face (n = 1, 4%).
Based on the International Society of Lymphology (ISL) stages, stage 3 lymphedema was the most common (n = 14, 52%), followed by stage 2 (n = 10, 37%) and stage 1 (n = 3, 11%). The average difference in volume between the involved limb and the normal limb was 16%. On lymphoscintigraphy images, apparent dermal backflow with or without axillary/inguinal lymph node uptake was observed in all patients, and in the case of lymphoscintigraphy grade, most patients (n = 19) showed total lymphatic obstruction (stage 4–6) in the involved limb. Indocyanine-green (ICG) lymphography was also performed in all patients, and with respect to dermal backflow stages (0–V), most patients showed a stardust/diffuse pattern in majority of the involved limbs at stages IV (n = 15) and V (n = 7) (Fig. 1, Table 1).
Four of the patients underwent lymphovenous anastomosis (LVA) at Hereditary Lymphedema Clinic, Seoul National University Bundang Hospital (Seongnam, South Korea), and one of these patients underwent simultaneous liposuction. Regarding history of previous surgery at other hospitals, liposuction (n = 2), LVA (n = 1), vascularized lymph node transfer (n = 1), and stem cell therapy (n = 1) were recorded.
A 38-year-old female presented with stage II lymphedema on her bilateral hand and stage III lymphedema on her bilateral leg, below the knee (Case 1 in Table 2). The age of onset for edema was age 11; however, the patient did not receive proper diagnosis or treatment until age 17, when she first developed cellulitis on her right foot and was subsequently hospitalized.
After primary lymphedema was diagnosed through radioisotope lymphoscintigraphy and clinical presentation, the patient developed similar symptoms in both upper extremities and continued rehabilitation treatment, including complex decongestive therapy and manual lymphatic drainage for both arms and legs. In the case of the lower extremities, there was no further change from stage III lymphedema, and the appearance was stationary. However, in the case of the upper extremities, lymphedema worsened from stage I to II despite recent rehabilitation treatment. The patient thus took leave of absence from her job and focused on her treatment. She then visited our clinic for LVA of both upper extremities.
Lymphoscintigraphy showed that the uptake in the left axillary lymph node was decreased, whereas the uptake in the left antecubital lymph node was increased; mild dermal backflow was observed in both forearms (Fig. 2). In the ICG examination, dermal backflow and lymphatic retention were observed in both forearms; however, the left side showed a more severe pattern than the right side (Fig. 3). Additionally, the patient’s mother had similar but milder lower leg primary lymphedema and also underwent genetic testing. Similar symptoms were not confirmed in other family members, and the patient’s father was not tested.
The patient then underwent LVA at two sites on each arm. Before surgery, the location of anastomosis was selected using ICG lymphangiography and high frequency ultrasonography (Fig. 4.). The patient underwent two successful LVAs on each side through a 2-cm incision and was discharged the next day without any complications from surgery. Approximately 10 months after the surgery, the patient's upper extremity lymphedema reduced to stage I, and the edema almost disappeared. She also eventually returned to work.
Germline variants of lymphedema-related genes
The average coverage depth in the target regions of the WES panel was 160.7X. On average, 92.8% of the bases had coverage ≥ 10X (45.2–99.5%). Among the 27 patients, eight variants of interest were detected in eight patients: two likely pathogenic variants and six variants of uncertain significance (VUSs) (Table 1).
A nonsense variant of CELSR1, c.8446C>T (p.Gln2816*), and a frameshift variant, c.8871_8872del (p.Cys2957*), were detected in the patient presented as case 1 (Table 2). c.8446C>T, which was classified as a likely pathogenic variant, was also detected in the patient’s symptomatic mother who was included in the study group. c.8871_8872del, which results in a premature termination codon in the penultimate exon, was classified as a VUS. This variant is expected to result in the loss of less than 2% of the protein, and the role of the truncated region is unknown. The patient’s mother did not harbor this variant; however, since her asymptomatic father was not tested, it could not be confirmed whether he harbored the variant as well.
Another pathogenic variant, MPI c.13C>T (p.Arg5*), was detected in case 4 (Table 1). The MPI gene is associated with congenital disorder of glycosylation, type Ib, which is inherited in an autosomal recessive pattern . However, the patient carrying this variant did not have any other symptoms related to this diagnosis. Hence, this variant could not be confirmed as a genetic cause for her lymphedema. She also had three VUSs in other genes (TIE1, FLT4, and PIEZO1), which can possibly be reclassified as variants of interest given additional evidence.