Abstract
Pycnodysostosis is a rare autosomal recessive disorder caused by mutations in the cysteine protease Cathepsin K gene located on chromosome 1q21. It has a well characterized skeletal phenotype which include short stature, generalized increased bone density with propensity of fractures, open calvarial sutures and fontanelle, dental abnormalities, obtuse mandibular angle, resorption of lateral end of clavicle, acro-osteolysis, and in some cases visceromegaly. Central nervous system involvement is very rare and porencephalic cysts has been reported only once, the cause being hypothesised to be an imbalance between the growing brain, its vascular supply and intraventricular fluid pressure. We had a patient with bilateral frontal lobe porencephalic cysts; the patient presenting with complex partial seizures. Cathepsins have been found to be involved in neurological diseases and role of proteases has been well established in gliosis.