To the Editor,
We present the case of a kidney recipient who recently underwent laparoscopic surgery for an adrenal myelolipoma associated with primary hyperaldosteronism. Myelolipomas are rare tumours; they are benign, grow slowly, and vary in size. They are made up of adipose and haematopoietic tissue. These tumours are typically non-functional and if they reach a large size, they can cause pain, pressure on adjacent organs and acute intratumoural or retroperitoneal bleeding.
The patient was a male aged 54 years, obese and a smoker, with long-standing hypertension (HT) and chronic kidney disease (CKD) secondary to malignant nephroangiosclerosis that was diagnosed by kidney biopsy in 2000. He started peritoneal dialysis in 2006 and underwent a deceased donor transplant in 2008. Previous x-ray studies already showed a right adrenal mass compatible with a myelolipoma; in 2005, it measured 5*5.4cm in diameter. When we were monitoring the patient’s CKD in our department, the patient also presented persistent hypokalaemia due to hyperreninemic hyperaldosteronism secondary to the underlying disease (malignant HT), which ruled out the possibility of a functional adrenal mass. However, as part of the pre-transplant study in 2008, the patient underwent a CT-guided needle biopsy of the adrenal mass, and the results from the histological study suggested a myelolipoma, thus confirming the initial diagnosis. As the tumour was benign, it did not contraindicate kidney transplantation.
During the two-year outpatient monitoring period following the transplant, the patient presented refractory HT requiring six different hypotensive drugs to achieve rather poor blood pressure control. His renal function deteriorated slowly over this time, and he presented proteinuria and microhaematuria. The persistent hypokalaemia reappeared and doctors ordered a new hormonal study. This time, the study found high plasma aldosterone (1098pg/ml) and suppressed plasma renin activity (0.13ng/ml/h). The patient was then diagnosed with primary hyperaldosteronism and the CT and MRI scans were repeated; the adrenal mass had reached 12*5cm in diameter along the cranio-caudal plane and 10cm in diameter along the transversal plane. It contained mainly fatty tissue with dense soft tissue areas. The patient was referred to the General Surgery Department, and in March 2010, underwent laparoscopic right adrenalectomy with excellent and prompt recovery.
The histological study showed an adrenal myelolipoma with hyperplasia of the adrenal cortex (zona glomerulosa) secondary to the pressure exerted by the large size of the myelolipoma. This explained the patient’s primary hyperaldosteronism, even though the tumour was benign and non-functional.
We could reduce the hypotensive drugs by half in the post-operative phase. The patient now has excellent control over his hypertension with the aid of two hypotensive drugs and blood potassium levels are normal, which suggests that the renal hyperplasia was not bilateral and was clearly associated with the myelolipoma.
We found cases of myelolipomas associated with arterial HT in the literature, but the tumours have never been shown to be functional. Arterial HT was rather explained by renovascular causes, due to pressure exerted by the tumour, or associated with obesity or endocrine conditions such as Cushing’s syndrome or Conn’s syndrome. This case is exceptional as primary hyperaldosteronism was caused by a myelolipoma, which could possibly be explained by the pressure exerted on the adrenal gland by the large tumour.
