Atypical presentation of the Azerbaijani infant with pycnodysostosis: A case report with a de novo mutation

Pycnodysostosis is a rare, autosomal recessive illness that is generally pathognomonic. It is characterized by the postnatal onset of short limbs, small stature, and global hyperostosis, as well as acro-osteolysis with sclerosis of the terminal phalanges. It has been shown that approximately 30% of patients have parental consanguinity. This condition is brought on by a mutation in the cathepsin K (CTSK) gene. To date, 34 distinct CTSK mutations have been found in patients. This lysosomal enzyme helps break down bone matrix proteins, including some forms of collagen, and is mostly present in osteoclasts. Between 90 and 95 percent of all organic bone matrix is made up of type 1 collagen, which is still uncleaved. Unusual bone and dental development results from the accumulation of undigested collagen fibrils by these patients’ fibroblasts. Pycnodysostosis is a clinical characteristic that only occurs when cathepsin K is completely lost. About 10% of patients are found to have mental impairment. We present an infant with pycnodysostosis, undiagnosed before presentation at birth.