Clinical Manifestations of Pacak-Zhuang Syndrome in a Male Pediatric Patient

Abstract

We report an index case of a male patient who presented with all clinical manifestations of Pacak-Zhuang syndrome, including early-age polycythemia, multiple pheochromocytomas/paragangliomas, duodenal somatostatinoma, ocular findings. Sequencing analysis detected an EPAS1 mutation in all tumors tested, but not in the germline.

Introduction

About 30% of pheochromocytomas and extra-adrenal paragangliomas are hereditary and are associated with germline mutations in one of at least 19 different susceptibility genes.^1,2 These tumors are grouped based on major implicated signaling pathways and include cluster 1 or pseudohypoxic tumors (mutations in VHL, SDH gene family, FH, and EPAS1), and cluster 2 ( mutations in kinase receptor signaling and protein translation pathways, such as RET, NF1, KIF1Bβ, and TMEM127).^3–5

Pacak-Zhuang syndrome is a recently described syndrome resulting from somatic gain-of-function mutations in hypoxia-inducible factor 2α (HIF-2α) encoded by the EPAS1 gene which occurs early in embryogenesis.^6,7 Pacak -Zhuang syndrome is characterized by congenital polycythemia, multiple paragangliomas, and duodenal somatostatinoma and characteristic ocular findings. The first presentation is usually polycythemia diagnosed in early life (median 2 years). Pheocromocytomas and pargangliomas primarily nor-epinephrine producing occur at a median age of 17 years, eye involvement and elevation of erythropoietin are universal ⁸

To our knowledge there have been no reported cases of males presenting with the full spectrum of the disease including somatostatinoma.⁷

Case Presentation

A 20-year-old Caucasian male was diagnosed with early age onset polycythemia at the age of 2 years when he presented with a hemoglobin of 22 g/dl. The patient was managed with recurrent red cell apheresis. At 6.5 years of age, the patient developed recurrent headaches and restless leg syndrome and was diagnosed with attention-deficit/hyperactivity disorder. Polycythemia was managed with recurrent phlebotomies. Genetic testing for JAK2 and VHL germline mutations were negative. At the age of 15 years, an ophthalmologic examination revealed right optic disc edema, with decreased vision in the right eye, which further progressed to bilateral fibrovascular membrane formation overlying the optic nerve. A brain MRI showed protrusion of the right optic nerve head into the posterior aspect of the right globe with tortuosity of both optic nerves, but no obvious cause for these findings was found. Also, at that time, the patient was admitted to the intensive care unit with an episode of hypertensive crisis with blood pressure > 210/120 mmHg. Blood testing revealed markedly elevated plasma normetanephrines and chromogranin A. An abdominal CT scan demonstrated a 4.6 cm left suprarenal mass and a 2.7 cm mass in the organ of Zuckerkandl. The patient underwent laparoscopic left adrenalectomy and resection of the pelvic mass. Histopathology confirmed the diagnosis of left adrenal pheochromocytoma with microvascular invasion within the tumor capsule, and paraganglioma in the organ of Zuckerkandl. Mutational testing of both tumors revealed a Pro531Ser mutation at exon 12 of the EPAS1 gene. Germline examination was normal.

After surgery, the patient was monitored with whole body and abdominal MRI scans and plasma metanephrines every 6–12 months. Four months after surgery, he developed increasing headaches and fluctuating hypertension. Plasma normetanephrine was elevated at 1063 pg/mL (normal <= 148 pg/mL). Whole body MRI showed a 2.3 cm right suprarenal/adrenal mass, and 18F-fluorodihydroxyphenylalanine (¹⁸F-FDOPA) PET/CT revealed 4 additional lesions, in the right perirenal and pericaval area, in the left periaortic region, and in the right lateral wall of urinary bladder behind the ureter, which were suspected to be multiple or metastatic pheochromocytomas/paragangliomas. The patient underwent right adrenalectomy, with excision of three retroperitoneal paragangliomas, 2 on the right side and one on the left. The right lateral wall of urinary bladder lesion was not resected. Histopathologic examination showed a right adrenal pheochromocytoma, and aortic, caval, and right perirenal paragangliomas. Fourteen months post second surgery, the patient developed dysuria, with hypertension. An abdominal ultrasound and whole-body MRI scan showed an increase in the size of the right lateral urinary bladder wall mass to 1.7 × 1.7 × 1.2 cm, as compared to prior CT, which measured 0.6 × 0.7 cm. Resection of the intramural mass revealed a paraganglioma.

At the age of 19 years, the patient was found on follow-up imaging studies to have a duodenal lesion on ¹⁸F-FDOPA and CT scans (Figure 1). The patient underwent esophagogastroduodenoscopy, showing a mucosa-covered nodule in the duodenum, in the fold immediately proximal to the ampulla of Vater. Somatostatin levels were elevated (43–53 pg/ml) (normal value < =30 pg/ml). The patient underwent exploratory laparotomy for resection of the duodenal mass. Histopathologic examination of the specimen showed a 1.3 × 0.8 × 0.6 cm submucosal mass in the duodenum, histologically consistent with a well-differentiated neuroendocrine tumor (Figures 2A–B). By immunohistochemistry, the tumor was uniformly positive for somatostatin (Figure 2C), consistent with a somatostatin-producing neuroendocrine tumor. Whole genome, whole exome, and whole transcriptome sequencing analysis was done on the tumor sample, which confirmed an EPAS1 mutation, c.1591C>T; p.Pro531Ser, identical to the mutation detected previously in the left pheochromocytoma and the organ of Zuckerkandl paraganglioma. Allele frequency of EPAS1 mutation in the duodenal somatostatinoma was 27% on whole genome sequencing, 23% on whole exome sequencing, and 34% on transcriptome sequencing. Chromosomal copy number analysis showed chromosomal partial loss of 19p and chromosomal partial gain of 9q. Estimated tumor sample purity was 42.7%.

Figure 1:

Anterior maximal intensity projection image of ¹⁸F-FDOPA PET/CT. Black arrow indicates site of somatostatinoma in the region of the duodenum. Red arrows identify sites of paragangliomas (top arrow – thoracic paravertebral; middle arrow – presacral; bottom arrow – low right pelvis adjacent to dome of the bladder).

Figure 2:

A. Hematoxylin and eosin (H&E)-stained sections of the duodenal mass (A) show a well-differentiated neuroendocrine tumor in the wall of the duodenum (A), consisting of tumor cells with uniform “salt and pepper” nuclei and tubuloacinar arrangement (B). The tumor cells are uniformly positive for somatostatin by immunohistochemistry (C).

Discussion

We present an index case of a male who developed the full spectrum of Pacak-Zhuang syndrome comprising polycythemia at an early age, multiple paragangliomas, bilateral pheochromocytoma, duodenal somatostatinoma, and characteristic ocular features.^7,9 Whole genome, exome and, transcriptome sequencing of the duodenal somatostatinoma showed an EPAS1 P531S mutation and 19p partial chromosomal loss and 9q partial chromosomal gain. The mutation was not detected in the germline DNA. This mutation is acquired postzygotically and distributed in a somatic mosaic fashion; in some reported patients, the EPAS1 mutation was detected at a lower frequency in some non-tumor cells namely leukocytes, buccal cells, hair and nails.^10,11

The EPAS1 mutation detected in our case is associated with stabilization and gain-of-function of HIF-2α protein because it directly affects the prolyl hydroxylase target residue, proline 531, impairing its hydroxylation and subsequent recognition of HIF-2α protein by VHL protein for subsequent proteasomal degradation.^6,7 Other reported EPAS1 mutations found to be associated with this syndrome affect the vicinity of the prolyl hydroxylase residues; examples include c.1588G>A p.A530T, c.1595A>G p.Y532C, c.1589C>T p.A530V, and c.1586T>C p.L529P.⁷

Primary familial and congenital polycythemia is an autosomal dominant condition associated with increased erythropoietin sensitivity, due to EPOR gene mutation leading to truncated erythropoietin receptor, lacking the C-terminal negative regulatory domain.¹² Our case was negative for EPOR mutation, suggesting possibly a different mechanism for this phenomenon and emphasizes the need to consider this entity in the differential diagnosis of patients with congenital polycythemia. In the event that this syndrome is diagnosed, it is important to screen for pheocromocytomas and paragangliomas starting at age 8, perform yearly serum and urine metanephrines, perform MRI whole body imaging every 1–2 years, consider surgery when lesions are amenable with alpha adrenergic blockade and screen for somatostatinomas beginning at age 20.⁸

Abbreviations

EPAS1 gene

Endothelial PAS domain protein 1

MRI

Magnetic resonance imaging

CT

Computed tomography

VHL

Von-Hippel-Lindau

SDH

succinate dehydrogenase

FH

fumarate hydratase

RET

Rearranged during transfection

NF1

Neurofibromatosis type 1

KIF1Bβ

Kinesin family member 1B

TMEM127

Transmembrane protein 27

EPOR

Erythropoietin receptor