[Pycnodysostosis: about a case]

Pycnodysostosis is a very rare genetic disease of the bone characterized by osteocondensation associated with dysmorphic syndrome and growth retardation. This study aims to highlight the phenotypic abnormalities, the radiological signs, the therapeutic and evolutionary features of pycnodysostosis in a 11-year old child. The child was referred by his dentist for clinical evaluation. He was born to first-degree consanguineous parents and had recurrent spontaneous fractures since the age of 3 years. Clinical examination showed dysmorphic syndrome characterized by frontal hump, persistent anterior fontanelle, micrognathia, finger deformities, dental malposition, curved nails, asymmetric chest, lumbar spine scoliosis with severe growth retardation (-4DS). Skeletal X-rays showed bony densification of the skull base, persistent anterior fontanelle, dental malposition, diaphysometaphyseal densification of the long bones mainly at the level of the lower limbs with malunions and tapered phalanges of the hands. Bone densitometry was normal. The diagnosis of pycnodysostosis was retained based on the clinical and radiological signs. Genetic counselling was proposed to the family as well as dental and orthopaedic treatment. Pycnodysostosis is a rare disorder; diagnosis is sometimes difficult and delayed posing diagnostic problem due to its resemblance with osteoporosis. Treatment is essentially based on fractures and dental caries prevention.