Bone Abstracts

Introduction: Niemann–Pick disease (NPD) is a rare autosomal recessive lysosomal lipid storage disorder. It is caused by mutations of genes which products are involved in the metabolism of sphingolipids. Their dysfunction causes sphingomyelin to accumulate in different organs which leads to progressive multisystemic disorder. Types A and B NPD are caused by mutations in sphingomyelin phosphodiesterase-1 gene with deficiency of acid sphingomyelinase (ASM). Types C and D NPD have normal or reduced sphingomyelinase activity but differ pathogenetically from types A and B. The various types share common clinical features and the severity of the disease varies depending on the gene mutation, enzyme deficiency and the system involved. The estimated incidence of types A and B NPD is 1:25 0000 and of type C is 1:150 000 live births.

Methods: A 34 year-old man with a family history of NPD type B was observed for pain and limited range of motion in both hip and knee joints.

Results: The clinical, biochemical and imaging data showed reduced ASM activity, hepatosplenomegaly, neurological deficiency, bone abnormalities, joint contractures not due to synovitis and myositis ossificans. The latter were seen on X-ray as massive ossifications with amorphous character around the hip joints and the CT images showed multiple massive ossifications and exostoses around the iliac bones and greater trochanter bilateral. The ossifications were visible in the internal and external obtorator muscles, gluteus medius and minimus and more severe in quadratus femoris muscle. This confirmed the combination of NPD type B with myositis ossificans.

Conclusion: It is important to raise the awareness of this debilitating condition and the need of a multidisciplinary management of such patients. As there is no recognized effective treatment for this disorder the possibility for prenatal diagnosis through amniocentesis or chorionic villus sampling especially in familial cases is of great importance.