Aortic valve ochronosis: a rare manifestation of alkaptonuria

Surgical management of calcific valvular and coronary disease in a patient with alkaptonuria: a case report

Background

Alkaptonuria is a rare metabolic disease that causes an increase in homogentisic acid (HGA) due to a lack of enzymatic activity. Commonly, accumulation of HGA presents with dark discoloration of skin and other tissues, also known as ochronosis. Additionally, alkaptonuria can result in other clinical manifestations, including arthritis and cardiac disease. This case highlights alkaptonuria-related cardiac disease and challenges that cardiac surgery teams may face when treating this patient population.

Case summary

A 62-year-old male with a history of alkaptonuria, Hodgkin's lymphoma treated with chemoradiation, hypertension, and hyperlipidaemia originally presented with shortness of breath in the setting of known cardiac disease. Cardiac work-up demonstrated aortic stenosis, mitral stenosis, and multivessel coronary artery disease requiring aortic valve replacement, mitral valve replacement, and coronary artery bypass grafting. During the operation, significant discoloration of tissue was observed. This correlated with areas of severe calcification, which was noted throughout both valves. Extensive debridement was required prior to proceeding to valve replacements. Additionally, near-infrared spectroscopy failed to provide accurate measurements of cerebral oxygenation.

Discussion

Alkaptonuria is correlated with cardiovascular disease, particularly valvular disease. Intraoperatively, these patients may exhibit noticeable discoloration and severe calcification of various tissues. Additionally, traditional infrared-based methods of cerebral oxygenation monitoring may not be reliable; however, other options of cerebral monitoring may be feasible. With proper pre-operative planning, however, patients with alkaptonuria may safely undergo cardiac surgery.

Tale of a Black Heart!

Alkaptonuria is a rare condition of inborn error of metabolism. Association with aortic stenosis has been described; however, diagnosis at the time of valve replacement is infrequent. Recognition of this condition has potential management implications as the durability of prosthetic valves in such cases is unknown. We describe a case report which depicts these unique aspects.

A black heart: Aortic valve ochronosis secondary to alkaptonuria causing aortic stenosis

Alkaptonuria is a rare autosomal recessive genetic disorder where an accumulation of homogentisic acid in the tissues leads to ochronosis-a pathological dark pigmentation. It can affect various tissues and the weight bearing joints of the body, leading to degenerative arthropathy. On the rare occasion, it causes cardiac manifestations. We describe a case of aortic valve stenosis due to ochronosis secondary to alkaptonuria requiring aortic valve replacement.

Cardiovascular ochronosis

In this review, we summarize previously reported case reports (n=66) in which the presence of ochronotic pigment was found in one or more cardiovascular structures either at necropsy or after operative excision of a cardiac valve or portions of arteries or both. As illustration, we describe black pigment in operatively excised aortic valves and aorta in 2 patients, both probably examples of secondary ochronosis. Ochronosis appears to have fascinated a number of prominent historical figures in medicine, and this review also summarizes their important contributions to this topic.

Operating the blues

A 63‐year‐old man bearing most signs and symptoms (facial pigmentation, degenerative arthritis, and dark urine) pertinent to his known history of alkaptonuria underwent aortic valve replacement for critical aortic stenosis. Although rare, aortic stenosis is the most common cardiac manifestation of alkaptonuric ochronosis.