Bone metaplasia with hematopoietic marrow in a calcified aortic valve
Nicola Vitale MD, PhD, *Marcello Lo Mele MD, *Gilda Caruso MD
Departments of Cardiac Surgery and *Pathology, Policlinico Hospital, University of Bari, Italy.
A 63 year old male patient presented with aortic valve stenosis, coronary artery disease and left carotid artery stenosis > 60%. He was successfully operated upon of aortic valve replacement with a 21 mm Mira mechanical prosthesis (Baxter-Edwards, Copertino, CA), triple coronary artery bypass grafting and left internal carotid endoarterectomy. The patient was discharged home on the 7th postoperative day after an uneventful recovery.
Gross examination of the excised valve showed the common features of a calcified stenotic aortic valve: fibrosis and extensive calcification of the three leaflets (Figure 1 (A)). Histopatologic examination of the leaflets confirmed fibrosis and calcification of the outer layer, but also revealed, in the deeper layers, the unexpected and very rare presence of mature trabeculated bone with all the hematopoietic elements (Figure 1 (B)). The diagnosis was osseus metaplasia with functioning marrow in a calcified, stenotic aortic valve.
Heterotopic calcification occuring in the aortic valve is common. The calcium is deposited initially in the zona fibrosa. With accumulation, the spongiosa is involved and the connective tissue surrounding the deposit becomes loosened and may show a chronic inflammatory reaction. However, bone material in such a valve is extremely rare, and rarer still is the presence of functioning marrow in metaplastic ossification. This case of osseus metaplasia would have been undetected if it had not been for the aortic stenosis. Because of its extremely rare occurrence it is unknown whether bone metaplasia of the aortic cusps is prone to calcium deposit during its natural history.
Figure legend
Figure 1 (A) Excised aortic valve: gross examination. The valve is stenotic, fibrotic and extensively calcified with complete fusion of the three leaflets. Figure 1 (B) Aortic valve leaflet: microscopic examination (magnification x 4, hematoxylin and eosin). Underneath the endocardial layer there is fibrotic tissue with scleroialinosis and scattered foci of calcification. The inner layers are occupied by fatty tissue and osseus lamellae. The arrow indicates hematopoietic elements.
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