Qualitative or quantitative defects of perlecan

Qualitative or quantitative defects of perlecan encompass a group of rare genetic skeletal disorders caused by mutations in the HSPG2 gene, which encodes perlecan (heparan sulfate proteoglycan 2), a major component of basement membranes and cartilage. Perlecan plays critical roles in cartilage development, endochondral ossification, and maintenance of basement membrane integrity. Defects in perlecan lead to two main clinical entities: Schwartz-Jampel syndrome type 1 (SJS1) and Silverman-Handmaker type of dyssegmental dysplasia (DDSH). Schwartz-Jampel syndrome type 1 is characterized by myotonia (sustained muscle stiffness), skeletal dysplasia with short stature, joint contractures, and a distinctive facial appearance including blepharophimosis (narrowing of the eye openings), pursed lips, and a fixed facial expression. Skeletal abnormalities include platyspondyly, bowing of long bones, and epiphyseal and metaphyseal irregularities. Dyssegmental dysplasia Silverman-Handmaker type represents the severe, lethal end of the spectrum, presenting at birth with severe short-limbed dwarfism, anisospondyly (vertebral bodies of different sizes and shapes), encephalocele, and respiratory insufficiency, typically resulting in neonatal death. The body systems primarily affected include the musculoskeletal system, the nervous system (due to myotonia), and in severe cases the central nervous system. Treatment is largely supportive and symptomatic. For Schwartz-Jampel syndrome, management may include medications to reduce myotonia (such as carbamazepine or mexiletine), physical therapy, orthopedic interventions for skeletal deformities and contractures, and surgical correction of blepharophimosis. No curative therapy currently exists for perlecan deficiency disorders.

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