Chylolymphatic Mesenteric Cyst as a Possible Ketogenic Diet Complication

Abstract

The ketogenic diet (KD) is a high-fat, low-carbohydrate, adequate-protein diet used for a century to treat drug-resistant epilepsy. It has relatively mild adverse effects. We highlight a patient who developed severe gastrointestinal (GI) symptoms related to a chylolymphatic mesenteric cyst (CMC) after KD initiation.

This boy was born at 39 weeks weighing 3490 g after an uneventful term gestation. Growth and development were initially appropriate. At 6 months of age he developed seizures manifested by episodes of right head-turning, rightward gaze deviation, impaired responsiveness, sometimes with chewing movements, decreased tone on the left, and/or shaking of the right extremities. These episodes had an ictal electrographic correlate with a diffuse onset but better evolution on the right on continuous video electroencephalography (EEG). Interictally, EEG showed epileptiform discharges in multiple areas on the right, resulting in a diagnosis of focal seizures with impaired consciousness. An epilepsy gene panel identified a heterozygous, paternally inherited, autosomal recessive, pathogenic variant in the biotinidase gene (BTD) (c.1368A>C, p.Q456H). A chromosomal microarray showed a maternally inherited, 329 kb duplication within 11p14.3 (arr[GRCh37]11p14.3(21897259_22226105)x3 mat). Brain magnetic resonance imaging was normal.

Levetiracetam, zonisamide, and clobazam failed to control seizures. Biotin therapy was not trialed. Oxcarbazepine reduced seizures but was limited by diarrhea and poor sleep. At 22 months, he began a 3:1 KD but was discharged on 2:1 due to acidosis and hypoglycemia. His abdominal examination was unremarkable. His seizure burden decreased from two to four seizures per day to a few times per week within the first 3 months, during which his KD ratio was gradually increased to 2.75:1.

Three months after starting the KD, he experienced intermittent severe abdominal pain, vomiting, and diarrhea for 5 days. An abdominal computed tomography scan revealed a predominantly hypoattenuating soft tissue mass measuring 35 × 43 × 41 mm arising from the root of the mesentery, causing mass effect on small bowel loops and abutting on branches of the superior mesenteric vein and artery with mesenteric lymphadenopathy (Figure 1). He underwent exploratory laparotomy with resection of a 5 cm chylous-appearing cystic mass in the mesenteric root, along with an 11 cm segment of adjacent small bowel, followed by re-anastomosis (Figure 2). Postoperatively, symptoms resolved, and tolerance to a 2.75:1 KD improved. His last seizures occurred immediately after surgery. He was weaned off oxcarbazepine 10 months after diet initiation, and he was weaned off the diet 2 years after surgery. Now 7 years of age, he remains seizure-free with near-normal development and no cyst recurrence. He has had three normal EEGs, including one overnight on the diet and one after diet discontinuation.

We classified the abdominal mass in our patient as a CMC, a rare variant of a mesenteric cyst [1], although the pathological features were also consistent with a mesenteric cystic lymphangioma [1, 2]. Despite presumed histological differences, CMCs are classified as either mesenteric cysts or mesenteric cystic lymphangiomas [1, 2]. Both occur frequently in young children, arise along the GI tract from small intestine to colon, and may be located from the mesenteric base to the retroperitoneum [1, 3-5]. They may be congenital or acquired from trauma, infection, or lymphatic obstruction [1, 3, 5]. Clinical presentations range from incidental abdominal masses or vague pain/distention to an acute abdomen, depending on cyst size, location, and complications [1-5]. Due to the high fat content in KD, we hypothesize that the cyst became symptomatic because lipids drain into intestinal submucosal lymphatics and then into the mesenteric collecting vessels/nodes, causing rapid enlargement [6]. We are not aware of previous reports of this potential KD complication. We recommend including CMCs in the differential diagnosis for KD patients presenting with refractory GI symptoms or an acute abdomen.

Siefaddeen Sharayah: writing – original draft, writing – review and editing, resources, data curation, investigation, validation. Jennifer Griffith: writing – review and editing, validation. Brad W. Warner: validation, writing – review and editing. Liu Lin Thio: conceptualization, supervision, investigation, writing – review and editing, methodology, data curation.

The authors declare no conflicts of interest.