Pycnodysostosis; A Rare Disease Case Report

Pycnodysostosis is a rare disease with very few reported cased all over the world. It was first described in 1963 by Maroteaux and Lamy. It is also known as Toulouse-Lautrec syndrome, after a French artist, Henri de Toulouse Lautrec. The affected gene, CTSK, was first isolated in 1996. It is an autosomal recessive osteochondrodysplasia, characterized by disrupted function of osteoclasts. Incidence of this disease is 1.7 per 1 million births with a male to female ratio of 1:1 30% cases arise from consanguineous marriages.

[Family picnodisostosis, report of a case after 10 years of follow-up]

INTRODUCTION

Pycnodysostosis is a rare disease secondary to a mutation in gen 1q21 that codifies the cathepsin K, proteolitic enzyme implicated in the metabolism of osteonectin, osteopontin and type I colagen. Its global incidence is around 1-1.7 cases per million, without genre prevalences, it is clinically caracterized by short stature, craneal deformities, «birds face» and bone fragility with pathological fractures tendency predominantly affecting long bones and occasionally vertebral pedicles. Radiologically is characterized by sclerous bones with permeable medular cannel. Despite there are numerous clinical reports on medical literature, just a litlle describe families with more than one afected member and its followship is usually short-term.

OBJECTIVE

To analize clinical evolution of these afected patients.

MATERIAL AND METHODS

A retrospective, descriptive, observational study was reelized in three patients with diagnosis of pycnodisostosis, between July 2006 and March 2016.

RESULTS

different affection forms of pycnodisostosis where observed, some of them, atipical, as for example spondilolisis and a escapule fracture in one patien.

CONCLUSIONS

The present study could be the longest longitudinal report ever registered. By knowing the presented variety of manifestations and complications, the reader could select the best treatment method for each case.

Traumatic cervical spine injuries in a patient with pycnodysostosis

Pycnodysostosis is a rare hereditary disease, characterized by systemic bone sclerosis. Susceptibility to long bone fractures is characteristic, whereas vertebral fractures are extremely rare. We report a case of a 21-year-old man with a past history of pycnodysostosis and spontaneous leg fractures who was admitted in hospital for a neck pain after a banal fall. Radiological examination revealed C1-C2-C3 posterior arch fractures with a C3-C4 left articular fracture dislocation. A surgical stabilization was decided but refused by the patient. To the best of our knowledge, this is the first publication that reports pycnodysostosis with cervical spine traumatic staged injuries.

Pycnodysostose: à propos d’un cas

La pycnodysostose est une maladie osseuse génétique très rare associant une ostéocondensation, un syndrome dysmorphique et un retard de croissance. Rappeler les anomalies phénotypiques, les signes radiologiques, la prise en charge thérapeutiques et évolutifs de la Pycnodysostose chez un enfant de 11 ans. Enfant de 11 ans, a été réferé par son dentiste pour évaluation de son état clinique. Il est de parents consanguin de premier degré, qui présentait depuis l'âge de 3 ans des fractures spontanées à répétition. L'examen trouvait un syndrome dysmorphique fait de bosse frontale, fontanelle antérieure persistante, micrognathie, malformations des doigts, malposition dentaire, ongles incurvées, thorax asymétrique, attitude scoliotique du rachis dorsal, avec retard statural important (-4DS). Les radiographies du squelette montraient une densification des os de la base du crâne, une persistance de la fontanelle antérieure, une malposition dentaire, une densification diaphysaire et métaphysaire des os longs prédominants au niveau des membres inférieurs avec présence des cals vicieux et des phalanges grêles des mains. L'ostéodensitométrie était normale. Devant les signes cliniques et les manifestations radiologiques, le diagnostic retenu est une pycnodysostose. Un conseil génétique a été proposé pour la famille ainsi qu'une prise en charge dentaire et orthopédiques. La pycnodysostose est une entité rare de diagnostic parfois difficile et tardif, elle pose un problème du diagnostic avec l'ostéoporose. Le traitement est essentiellement préventif des fractures et des caries dentaires.

A case report of pycnodysostosis with atypical femur fracture diagnosed by next-generation sequencing of candidate genes

RATIONALE

Pycnodysostosis is a rare autosomal recessive skeletal dysplasia characterized by short stature, craniofacial dysmorphism, acro-osteolysis, osteosclerosis, and brittle bone with poor healing. Pycnodysostosis results from the deficient activity of cathepsin K, a lysosomal cysteine protease that is encoded by CTSK.

PATIENT CONCERNS

We report a Korean adult patient with pycnodysostosis and atypical femur fracture whose diagnosis was confirmed by next-generation sequencing (NGS) of candidate genes. A 41-year-old female patient was presented with a left femur fracture after falling down. Underlying sclerotic bone disease was suspected as a radiographic skeletal survey showed thickened cortical bones, and the total body bone density was increased (T score was 5.3, and Z score was 4.9).

DIAGNOSES

We performed candidate gene sequencing of various sclerotic bone diseases for the differential molecular diagnosis of underlying sclerosing bone disease. Two heterozygous variants of CTSK were detected. One was a frameshift variant in exon 5, c.426delT (p.Phe142Leufs*19), which was previously reported, and the other was a novel missense variant in exon 6, c.755G>A (p.Ser252Asn). Sanger sequencing of CTSK confirmed the 2 heterozygous variants and thus the patient was diagnosed with pycnodysostosis.

INTERVENTIONS

The patient had emergency surgery for subtrochantic femoral fracture.

OUTCOMES

After 4 months of surgery, the patient had almost a full range of hip and knee movements and radiographs show the substantial bridging callus across the fracture.

LESSONS

Candidate gene sequencing could be a useful diagnostic tool for the genetically heterogeneous skeletal dysplasia group, especially in cases with a mild or atypical clinical phenotype.

Miscellaneous Bone Disorders

This chapter deals with a few of the important childhood bone disorders associated with high bone mass as well as conditions associated with fragility fractures and limb deformities that have not been addressed in previous chapters. A couple of skeletal dysplasias that can sometimes be confused with rickets are also dealt with in this chapter.