National Center for Advancing and Translational Sciences Genetic and Rare Diseases Information Center, a program of the National Center for Advancing and Translational Sciences

Pycnodysostosis


Other Names:
Pyknodysostosis; PKND; PYCD
Categories:
Pycnodysostosis impacts bone growth and is present from birth. Symptoms include a large head and high forehead, undeveloped facial bones, and short fingers and toes. People with pycnodysostosis may have short stature, dental abnormalities, brittle bones, and delayed closure of the skull bones. Bones may become more brittle with age. Other complications like trouble breathing during sleep (sleep apnea) and bone infections may occur. Pycnodysostosis is caused by a CTSK gene that is not working correctly and inherited in an autosomal recessive pattern. The diagnosis of pycnodysostosis is based on clinical examination and X-ray findings, and is confirmed by genetic testing. Treatment is based on managing the symptoms.[1][2][3]
Last updated: 6/5/2020
The following list includes the most common signs and symptoms in people with pycnodysostosis. These features may be different from person to person. Some people may have more symptoms than others and symptoms can range from mild to severe. This list does not include every symptom or feature that has been described in this condition.

Signs and symptoms may include:[2][3]
  • Short bones
  • Loss of bone tissue from the hands (acro-osteolysis)
  • Delayed closure of the skull bones
  • Underdeveloped facial bones
  • Thickening of the face and skull bones
  • Dental anomalies
Many of the signs of pycnodysostosis are present at birth. People with pycnodysostosis are usually shorter than average and have normal intellectual development. Bone infections (osteomyelitis) and trouble breathing during sleep (sleep apnea) may also occur. The bones often get more brittle with time.[2]
Last updated: 6/8/2020

This table lists symptoms that people with this disease may have. For most diseases, symptoms will vary from person to person. People with the same disease may not have all the symptoms listed. This information comes from a database called the Human Phenotype Ontology (HPO) . The HPO collects information on symptoms that have been described in medical resources. The HPO is updated regularly. Use the HPO ID to access more in-depth information about a symptom.

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Medical Terms Other Names
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HPO ID
80%-99% of people have these symptoms
Abnormal fingernail morphology
Abnormal fingernails
Abnormality of the fingernails
[ more ] 		0001231
Abnormal pelvis bone ossification 0009106
Abnormal vertebral morphology 0003468
Abnormality of epiphysis morphology
Abnormal shape of end part of bone
0005930
Abnormality of the clavicle
Abnormal collarbone
0000889
Brachycephaly
Short and broad skull
0000248
Brachydactyly
Short fingers or toes
0001156
Delayed eruption 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 retrusion
Decreased size of midface
Midface deficiency
Underdevelopment of midface
[ more ] 		0011800
Narrow palate
Narrow roof of mouth
0000189
Osteolysis
Breakdown of bone
0002797
Persistent open anterior fontanelle 0004474
Recurrent fractures
Increased fracture rate
Increased fractures
Multiple fractures
Multiple spontaneous fractures
Varying degree of multiple fractures
[ more ] 		0002757
Short distal phalanx of finger
Short outermost finger bone
0009882
Short stature
Decreased body height
Small stature
[ more ] 		0004322
Short toe
Short toes
Stubby toes
[ more ] 		0001831
Skeletal dysplasia 0002652
30%-79% of people have these symptoms
Abnormality of dental morphology
Abnormality of dental shape
Abnormally shaped teeth
Deformity of teeth
Dental deformity
Dental malformations
Malformed teeth
Misshapen teeth
Misshapened teeth
[ more ] 		0006482
Blue sclerae
Whites of eyes are a bluish-gray color
0000592
Bone pain 0002653
Proptosis
Bulging eye
Eyeballs bulging out
Prominent eyes
Prominent globes
Protruding eyes
[ more ] 		0000520
Ridged nail
Grooved nails
Nail ridging
[ more ] 		0001807
Wormian bones
Extra bones within cranial sutures
0002645
5%-29% of people have these symptoms
Abnormal pattern of respiration
Abnormal respiratory patterns
Unusual breathing patterns
[ more ] 		0002793
Abnormality of the skin 0000951
Anemia
Low number of red blood cells or hemoglobin
0001903
Cognitive impairment
Abnormality of cognition
Cognitive abnormality
Cognitive defects
Cognitive deficits
Intellectual impairment
Mental impairment
[ more ] 		0100543
Hepatomegaly
Enlarged liver
0002240
Hydrocephalus
Too much cerebrospinal fluid in the brain
0000238
Hyperlordosis
Prominent swayback
0003307
Kyphosis
Hunched back
Round back
[ more ] 		0002808
Narrow chest
Low chest circumference
Narrow shoulders
[ more ] 		0000774
Osteomyelitis
Bone infection
0002754
Splenomegaly
Increased spleen size
0001744
Percent of people who have these symptoms is not available through HPO
Abnormality of pelvic girdle bone morphology
Abnormal shape of pelvic girdle bone
0002644
Abnormality of the thorax
Abnormality of the chest
0000765
Absent frontal sinuses 0002688
Autosomal recessive inheritance 0000007
Carious teeth
Dental cavities
Tooth cavities
Tooth decay
[ more ] 		0000670
Delayed eruption of permanent teeth
Delayed eruption of adult teeth
0000696
Delayed eruption of primary teeth
Delayed eruption of baby teeth
Delayed eruption of milk teeth
Late eruption of baby teeth
Late eruption of milk teeth
[ more ] 		0000680
Hypodontia
Failure of development of between one and six teeth
0000668
Increased bone mineral density
Increased bone density
0011001
Micrognathia
Little lower jaw
Small jaw
Small lower jaw
[ more ] 		0000347
Osteolytic defects of the distal phalanges of the hand 0009839
Persistence of primary teeth
Delayed loss of baby teeth
Failure to lose baby teeth
Retained baby teeth
[ more ] 		0006335
Prominent nose
Big nose
Disproportionately large nose
Increased nasal size
Increased size of nose
Large nose
Pronounced nose
[ more ] 		0000448
Prominent occiput
Prominent back of the skull
Prominent posterior skull
[ more ] 		0000269
Scoliosis 0002650
Spondylolisthesis
Displacement of one backbone compared to another
Slipped backbone
[ more ] 		0003302
Spondylolysis 0003304
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Last updated: 7/1/2020
Pycnodysostosis occurs when the CTSK gene is not working correctly.[3] DNA changes known as pathogenic variants are responsible for making genes work incorrectly or sometimes, not at all.
Last updated: 6/8/2020
Pycnodysostosis is inherited in an autosomal recessive pattern.[3] All individuals inherit two copies of each gene. Autosomal means the gene is found on one of the numbered chromosomes found in both sexes. Recessive means that both copies of the responsible gene must be altered to have the condition.
  
People with autosomal recessive conditions inherit one alteration from each of their parents. The parents, who each have one gene alteration, are known as carriers. Carriers of an autosomal recessive condition typically do not have any signs or symptoms (they are unaffected). When two carriers of an autosomal recessive condition have children, there is a 25% (1 in 4) chance to have a child with the condition. 
Last updated: 6/8/2020
Pycnodysostosis is diagnosed through a clinical examination, the symptoms, and X-rays of the affected bones. Genetic testing may be used to confirm the diagnosis.[2]
Last updated: 6/8/2020

Testing Resources

  • The Genetic Testing Registry (GTR) provides information about the genetic tests for this condition. The intended audience for the GTR is health care providers and researchers. Patients and consumers with specific questions about a genetic test should contact a health care provider or a genetics professional.
The treatment for pycnodysostosis is based on managing the symptoms. Treatment may include surgery, dental procedures, and medications for pain.[2][3]

Specialists involved in the care of someone with pycnodysostosis may include:
  • Orthopedist
  • Dentist
  • Otolaryngologist
  • Orthodontist
  • Maxillofacial surgeon
Last updated: 6/8/2020
There are about 200 reported cases of pycnodysostosis in the literature. It has been estimated that one to three people in 1,000,000 have pycnodysostosis. The exact number of people with this condition is unknown.[2][4][5]
Last updated: 6/8/2020

If you need medical advice, you can look for doctors or other healthcare professionals who have experience with this disease. You may find these specialists through advocacy organizations, clinical trials, or articles published in medical journals. You may also want to contact a university or tertiary medical center in your area, because these centers tend to see more complex cases and have the latest technology and treatments.

If you can’t find a specialist in your local area, try contacting national or international specialists. They may be able to refer you to someone they know through conferences or research efforts. Some specialists may be willing to consult with you or your local doctors over the phone or by email if you can't travel to them for care.

You can find more tips in our guide, How to Find a Disease Specialist. We also encourage you to explore the rest of this page to find resources that can help you find specialists.

Healthcare Resources

Related diseases are conditions that have similar signs and symptoms. A health care provider may consider these conditions in the table below when making a diagnosis. Please note that the table may not include all the possible conditions related to this disease.

Conditions with similar signs and symptoms from Orphanet
Differential diagnoses include osteoporosis, osteopetrosis, cleidocranial dysplasia and idiopathic acroosteolysis (see these terms).
Visit the Orphanet disease page for more information.

Research helps us better understand diseases and can lead to advances in diagnosis and treatment. This section provides resources to help you learn about medical research and ways to get involved.

Patient Registry

  • The Lysosomal Disease Network is a team of doctors, nurses, research coordinators, and research labs throughout the U.S., working together to improve the lives of people with this condition through research. The Lysosomal Disease Network has a registry for patients who wish to be contacted about clinical research opportunities.

These resources provide more information about this condition or associated symptoms. The in-depth resources contain medical and scientific language that may be hard to understand. You may want to review these resources with a medical professional.

Where to Start

  • The National Organization for Rare Disorders (NORD) has a report for patients and families about this condition. NORD is a patient advocacy organization for individuals with rare diseases and the organizations that serve them.

In-Depth Information

  • The Monarch Initiative brings together data about this condition from humans and other species to help physicians and biomedical researchers. Monarch’s tools are designed to make it easier to compare the signs and symptoms (phenotypes) of different diseases and discover common features. This initiative is a collaboration between several academic institutions across the world and is funded by the National Institutes of Health. Visit the website to explore the biology of this condition.
  • Online Mendelian Inheritance in Man (OMIM) is a catalog of human genes and genetic disorders. Each entry has a summary of related medical articles. It is meant for health care professionals and researchers. OMIM is maintained by Johns Hopkins University School of Medicine. 
  • Orphanet is a European reference portal for information on rare diseases and orphan drugs. Access to this database is free of charge.
  • PubMed is a searchable database of medical literature and lists journal articles that discuss Pycnodysostosis. Click on the link to view a sample search on this topic.

Questions sent to GARD may be posted here if the information could be helpful to others. We remove all identifying information when posting a question to protect your privacy. If you do not want your question posted, please let us know.

  1. Farronato G, Salvadori S, Nolet F, Borgonovo A, Esposito L. Pycnodysostosis: review and case report. Minerva Stomatol. 2014; 63(6):229-237. https://pubmed.ncbi.nlm.nih.gov/25267152.
  2. Bizaoui V, Michot C, Baujat G, et al. Pycnodysostosis: Natural history and management guidelines from 27 French cases and a literature review. Clin Genet. 2019; 96(4):309-316. https://pubmed.ncbi.nlm.nih.gov/31237352.
  3. Gray ML, Su A, Cruciata G, Som PM. Pycnodysostosis in an Adult: A Case Report and Review of the Literature. Ear Nose Throat J. 2019; 98(10):627-628. https://pubmed.ncbi.nlm.nih.gov/31847556.
  4. de Oliveira EM, de Arruda JAA, Nascimento PAM, Neiva IM, Mesquita RA, Souza LN. An Update on Osteomyelitis Treatment in a Pycnodysostosis Patient. J Oral Maxillofac Surg. 2018; 76(10):2136.e1-2136.e10. https://pubmed.ncbi.nlm.nih.gov/30030999.
  5. Markatos K, Mavrogenis AF, Karamanou M, Androutsos G. Pycnodysostosis: the disease of Henri de Toulouse-Lautrec. Eur J Orthop Surg Traumatol. 2018; 28(8):1569-1572. https://pubmed.ncbi.nlm.nih.gov/29797092.
  6. Khoja A, Fida M, Shaikh A. Pycnodysostosis with Special Emphasis on Dentofacial Characteristics. Case Rep Dent. 2015 Nov 16; https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4663328/.