Perivascular fibrosis in the bone marrow in sickle cell disease

Magnetic resonance imaging of bone marrow in homozygous sickle cell disease (hemoglobin [Hb] SS) shows nonhomogeneous, mottled signals that increase with age and number of crises. The pattern of these signals is reminiscent of the underlying vascular architecture, but histopathology of this tissue has not been adequately studied.

To elucidate the histopathology of blood vessels in the bone marrow in sickle cell disease.

Retrospective histochemical morphometric study of bone marrow arteries by point counting in HbSS (13 cases) and sickle cell Hb C (HbSC) (8 cases) compared to nonanemic normal controls (HbAA) (10 cases). All patients were nondiabetic, normotensive, younger than 37 years, and matched for age group.

The mean point count for perivascular fibrous tissue was significantly greater in the HbSS group (P <.001) in both small (P <.001) and medium-sized (P =.002) vessels, and in both age groups (pediatric, P <.001; adult, P =.005) compared with the HbAA group. Additional analysis showed the difference was significant in HbSS pediatric small vessels (P <.001) and in pediatric and adult medium vessels (P =.045 and P =.03, respectively). Ratios of fibrous tissue to muscle showed proportionately greater fibrous tissue in HbSS pediatric small (P <.001) and medium-sized vessels (P =.02), and in adult large vessels (P =.03). Mean point counts for muscle were significantly decreased in HbSS small vessels when all ages were compared as a group (P =.02), but when compared by age groups, counts were significantly increased in adult HbSS medium-sized vessels (P =.01). Overall mean point counts for muscle and fibrous tissue in the HbSC group were intermediate between those of the HbSS and HbAA groups, but were not significantly different from counts in the HbAA group (P =.78 and P =.35, respectively).

In sickle cell disease, arterial vessels in the bone marrow show significantly increased fibrous connective tissue and changes in muscle that vary with age and vessel size.