Pyknodysostosis is a genetic disease that is inherited with an autosomal recessive pattern. It is caused by a mutation in chromosome 1q21, which, in turn, leads to the production of a defective cystine protease, an enzyme found in lysosomes, called cathepsin K (CTSK), which normally breaks down type 1 collagen fibers. The end result of this process is dense, brittle bones [1]. Pyknodysostosis is rare, and some cases have been linked with consanguinity [2]. Males are predominantly affected, while the onset of the disease is often observed in children and young adults [3].

Clinically, the condition presents with dental abnormalities such as crowding due to persisting deciduous teeth, a tendency to form dental caries, dental abscesses, enamel erosion, hypercementosis and short dental roots [4] [5]. Further deformities in the oral cavity include macroglosia and a ridged or high-arched palate [6].

Musculoskeletal signs include dwarfism, limb and digit anomalies, frequent fractures, poorly formed clavicles and craniosynostosis (premature closure of sutures in infants, resulting in abnormal skull shape). Moreover, other features that include respiratory problems, and Arnold-Chiari malformation, have been described [7]. There are variant genotypes of the condition that present with more severe, earlier-onset symptoms [8]. Of note, individuals who suffer from pyknodysostosis are not typically anemic, and this can help distinguish the disease from similar bone disorders such as osteopetrosis.

• Short Stature

  […] pyknodysostosis [ pik″no-dis″os-to´sis ] a hereditary syndrome of dwarfism, osteopetrosis, and skeletal anomalies of the cranium, digits, and mandible. pyk·no·dys·os·to·sis ( pik'nō-dis'os-tō'sis ), [TA] A condition characterized by short stature, delayed [medical-dictionary.thefreedictionary.com]

  Pyknodysostosis is a rare, genetic, autosomal recessive condition characterized by short stature, generalized bone sclerosis, and oral manifestations such as maxillary atresia and an increase of the mandibular angle. [ncbi.nlm.nih.gov]

  Patients present in early childhood with: short stature, particularly limbs delayed closure of cranial sutures frontal and occipital bossing short broad hands and hypoplasia of nails multiple long bone fractures following minimal trauma Pyknodysostosis [radiopaedia.org]

  The short stature is variable but moderate (1.35m to 1.50m). [orpha.net]

• Anemia

  Bony overgrowths may narrow the marrow cavity and cause cytopenias ranging from anemia to pancytopenia. Extramedullary hematopoiesis may occur, resulting in hepatosplenomegaly; consequent hypersplenism may worsen anemia. [merckmanuals.com]

  Very rarely, the disease is associated with anemia, hepatosplenomegaly, hematologic alterations, respiratory distress and sleep apnea. The short stature is variable but moderate (1.35m to 1.50m). [orpha.net]

  Perversions Much More Pleasurable And Fantastic renal osteodystrophy sickle cell myelofibrosis osteopetrosis pyknodysostosis mets mastocytosis paget's athlete fluorosis ddx: diffuse increase in bone density (mnemonic 2) MARBLE myelofibrosis/mastocytosis anemia [cueflash.com]

  […] is associated to this characteristics. [2], [3] Kumar et al, reported a case in which a 6-year-old patient, with the clinical and radiological characteristics of pyknodysostosis, also showed anemia and hepatosplenomegaly, commonly found in osteopetrosis [jisppd.com]

• Painter

  The disease is named after the French painter Henri de Toulouse-Lautrec, since Maroteaux and Lamy, the first describers of pyknodysostosis, concluded from complaints found in letters to his friends and relatives that he was suffering from pyknodysostosis [accessanesthesiology.mhmedical.com]

  The most famous sufferer is Henri de Toulouse-Lautrec who went on to be a painter fully active in society of his day. [syndromespedia.com]

  The French painter, Henri de Toulouse Lautrec (1864–1901), is believed to have had the disorder 2. [nature.com]

  These authors speculated that the famous French painter, Toulouse-Lautrec (1864-1901), may have suffered from this disease. 1 The disease shows equal sex distribution with high parental consanguinity, having an incidence of 1.7 per 1 million births. 2 [synapse.koreamed.org]

• Respiratory Distress

  Very rarely, the disease is associated with anemia, hepatosplenomegaly, hematologic alterations, respiratory distress and sleep apnea. The short stature is variable but moderate (1.35m to 1.50m). [orpha.net]

• Failure to Thrive

  It causes weakness, stunted stature, and failure to thrive. Bones appear dense on x-rays, and cerebral calcifications are seen; renal tubular acidosis is present, and RBC carbonic anhydrase activity is decreased. [merckmanuals.com]

  Case presentation An 11-year-old Indian boy from Bijapur district of Karnataka State was referred to the paediatric unit of the Al Ameen Medical College Hospital with history of short stature, dysmorphic facies and failure to thrive for evaluation. [ncbi.nlm.nih.gov]

  […] to thrive for evaluation. [dx.doi.org]

• Hepatosplenomegaly

  In this article we report a case of 12 year old female from Punjab with pyknodysostosis having hepatosplenomegaly and simian crease. [ncbi.nlm.nih.gov]

  Very rarely, the disease is associated with anemia, hepatosplenomegaly, hematologic alterations, respiratory distress and sleep apnea. The short stature is variable but moderate (1.35m to 1.50m). [orpha.net]

  Extramedullary hematopoiesis may occur, resulting in hepatosplenomegaly; consequent hypersplenism may worsen anemia. The skeleton usually is radiologically normal at birth. [merckmanuals.com]

  Visceral manifestations such as hepatosplenomegaly are reported but are uncommon. Rare manifestations of this condition include extramedullary hematopoiesis and obstructive airways disease. Complications Only gold members can continue reading. [radiologykey.com]

• Dental Caries

  Zarif Najafi Keywords: Dental Caries, Sweetening Agents, Students, Abstract Pyknodysostosis is a rare bone disease that has autosomal dominant trait. [jdt.tums.ac.ir]

  Clinically, the condition presents with dental abnormalities such as crowding due to persisting deciduous teeth, a tendency to form dental caries, dental abscesses, enamel erosion, hypercementosis and short dental roots. [symptoma.com]

  Herein we reported a case of pycnodysostosis, showingshort stature with widening of the sutures, unfused anterior andposterior fontanelles, crowding of teeth with dental caries and typicalradiological features associated with ichthyosis vulgaris and palmoplantarkeratoderma [ama.ba]

• Eruptions

  […] of teeth Delayed eruption Delayed teeth eruption Delayed tooth eruption Eruption, delayed Late eruption of teeth Late tooth eruption [ more ] 0000684 Frontal bossing 0002007 High forehead 0000348 Malar flattening Zygomatic flattening 0000272 Midface [rarediseases.info.nih.gov]

  Of particular interest is that he wore complete dentures and had a chief complaint of pain arising from partially erupting teeth under the denture. To our knowledge this is the first reported case from the Philippines. [ncbi.nlm.nih.gov]

  Very excellent delineation of unerupted and partially erupted teeth was obtained. [joomr.org]

  Dentition anomalies include delayed eruption and irregularities of the permanent teeth, with or without partial anodontia. [accessanesthesiology.mhmedical.com]

  Many of the teeth are unerupted or only partially erupted. Evaluation of follicles is limited. B, Scout topogram demonstrates Wormian bones ( arrows ) within the lambdoid suture. [ajnr.org]

The diagnosis, as well as the evaluation of the extent of pyknodysostosis, relies mainly on the clinical picture, as well as on imaging modalities. The commonly used techniques are:

• X-rays - Findings may include delayed fontanelle and suture closure, skull bossing in the frontal and occipital bones, flat mandibular angle, beaked nose, paranasal sinuses lacking air spaces, osteosclerosis, short digits, aplastic phalanges and clavicles, distally widened femurs, and long bone fractures. There are also a number of spinal abnormalities such as pronounced lumbar lordosis, anomalous segmentation of vertebrae, especially in the cervical and lumbar regions, as well as sclerosis [1]. Generally, the bones throughout the skeleton will have increased radio-opacity due to increased density.
• Computerized tomography (CT) scanning - This may show hypoplastic sinuses and slow skeletal maturation, seen as delayed bone age [9].
• Magnetic resonance imaging (MRI) - Bone thickening may also be visualized through this technique.

Histological analysis of bone is carried out, and may demonstrate features such as attenuated central canals in the Haversian system and abnormal medullary canals [10]. Molecular testing to detect the mutation in the gene coding for CTSK confirms the diagnosis [10].

• Increased Bone Density

  Densitometry measurements revealed values of up to 291% of age-matched normal controls; this increased bone density was mainly in the trabecular bone and not in the cortical bone. [ncbi.nlm.nih.gov]

  […] persistent open fontanelles and cranial sutures; however, it always involves the clavicle (a bone only rarely affected in pycnodysostosis) 1 and does not result in overall increased bone density. 2 Osteogenesis imperfecta patients present with multiple [sajr.org.za]

  This disorder is characterized by short stature, increased bone density (osteosclerosis/osteopetrosis), underdevelopment of the tips of fingers with absent or small nails, fragile bones that may fracture easily, abnormal or absent collarbone (clavicle [wa.kaiserpermanente.org]

Such patients must be placed under an oral hygiene prevention scheme, a treatment plan must be accurately designed and the patient must be constantly motivated.", keywords = "Craniofacial anomalies, Orthodontic treatment, Pycnodysostosis", author = "G [moh-it.pure.elsevier.com]

Management and treatment Management is symptomatic and multidisciplinary. It includes orthopedic monitoring, treatment of fractures, of which consolidation is sometimes slow, and static vertebral surveillance to detect frequent spondylolisthesis. [orpha.net]

This article outlines the clinical and radiographic characteristics of this condition based on the clinical case described and proposes an approach regarding the best form of treatment. [dx.doi.org]

Risk of infection and/or nonunion after such a surgical procedure was considered too great, and therefore the possibility of treatment by distraction osteogenesis of the maxilla was evaluated. [ncbi.nlm.nih.gov]

Prognosis The prognosis is favorable; the disease is not progressive. The documents contained in this web site are presented for information purposes only. [orpha.net]

Prognosis The prognosis for a person with Toulouse Lautrec Syndrome is generally good. The sufferer will be prone to fractures, but with care. Lifespan can be normal or near-normal. References: Avon SL. [syndromespedia.com]

[…] osteogenesis imperfecta, but are most often a normal variant Treatment Dental problems may require frequent oral care Genetic counseling if there is a family or personal history of cleidocranial dysostosis and the individual is planning to have children Prognosis [learningradiology.com]

However, prognosis is poor with HLA-mismatched grafts. Prednisone, calcitriol, and interferon gamma are effective in some cases. This type of osteopetrosis is autosomal recessive. [merckmanuals.com]

Etiology Pycnodysostosis is due to mutations in the gene encoding cathepsin K (localized to 1q21), a lysosomal enzyme secreted by osteoclasts, which allows the division of proteins of the bone matrix (collagen type I, osteonectin or osteopontin). [orpha.net]

Etiology Pyknodysostosis is an autosomal recessive congenital abnormality resulting in mutations in the CTSK gene at 1q21, which codes for cathepsin K. [radiologykey.com]

Summary Epidemiology It is very rare, the exact prevalence is unknown but it is less than 1/100,000. Clinical description The disease is discovered at variable ages, ranging from 9 months to 50 years. [orpha.net]

The discussion covers the phenotype spectrum, epidemiology, mode of inheritance, pathogenesis, and clinical profile of each condition, all of which is accompanied by a wealth of illustrations. [books.google.com]

In a format designed for quick reference, it provides complete information on the symptoms, pathophysiology, diagnosis, and treatment of all common and rare bone and mineral disorders. [books.google.com]

Pathophysiology Cathepsin K is a lysosomal cysteine protease that plays a key regulatory role in bone metabolism, abnormalities of which interfere with bone resorption and remodeling. [radiologykey.com]

Craniotomy was needed to evacuate the haematoma and prevent mortality. Extradural haematoma in this group of patients is rare, ours being the second case reported in literature. [ncbi.nlm.nih.gov]

Such patients must be placed under an oral hygiene prevention scheme, a treatment plan must be accurately designed and the patient must be constantly motivated. [moh-it.pure.elsevier.com]

Recognition of these signs is important in order to make the diagnosis and prevent possible complications. [sajr.org.za]

To prevent oral complications, maintenance of proper oral hygiene and regular dental visits is very important. Tooth extraction and other surgeries should be done carefully to prevent postextraction osteomyelitis. [contempclindent.org]

Regular checkups and dental hygiene are helpful for preventing complications. [syndromespedia.com]

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3. Kamak H, Kamak G, Yavuz I. Clinical, radiographic, diagnostic and cephalometric features of Pyknodysostosis in comparison with Turkish cephalometric norms: A case report. Eur J Dent. 2012;6(4):454–459.
4. Fleming KW, Barest G, Sakai O. Dental and facial bone abnormalities in pyknodysostosis: CT findings. AJNR Am J Neuroradiol. 2007;28 (1)132-134.
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8. Arman A, Bereket A, Coker A, et al. Cathepsin K analysis in a pycnodysostosis cohort: Demographic, genotypic and phenotypic features. Orphanet J Rare Dis. 2014;9:60.
9. Hunt NP, Cunningham SJ, Adnan N, Harris M. The dental, craniofacial, and biochemical features of pyknodysostosis: a report of three new cases. J Oral Maxillofac Surg. 1998;56(4):497-504.
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