Pycnodysostosis

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Disease Profile

Pycnodysostosis

1-9 / 1 000 000

US Estimated

Europe Estimated

Age of onset

Infancy

ICD-10

Q78.8

Inheritance

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.

Autosomal dominant A pathogenic variant in only one gene copy in each cell is sufficient to cause an autosomal dominant disease.

Autosomal recessive Pathogenic variants in both copies of each gene of the chromosome are needed to cause an autosomal recessive disease and observe the mutant phenotype.

X-linked
dominant X-linked dominant inheritance, sometimes referred to as X-linked dominance, is a mode of genetic inheritance by which a dominant gene is carried on the X chromosome.

X-linked
recessive Pathogenic variants in both copies of a gene on the X chromosome cause an X-linked recessive disorder.

Mitochondrial or multigenic Mitochondrial genetic disorders can be caused by changes (mutations) in either the mitochondrial DNA or nuclear DNA that lead to dysfunction of the mitochondria and inadequate production of energy.

Multigenic or multifactor Inheritance involving many factors, of which at least one is genetic but none is of overwhelming importance, as in the causation of a disease by multiple genetic and environmental factors.

Not applicable

Other names (AKA)

Pyknodysostosis; PKND; PYCD

Summary

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]

Symptoms

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]

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.

Medical Terms

Other Names

Learn More:

HPO ID

80%-99% of people have these symptoms

Abnormal clavicle morphology

Abnormal collarbone

0000889

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

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

Abnormal thorax morphology

Abnormality of the chest

0000765

Abnormality of pelvic girdle bone morphology

Abnormal shape of pelvic girdle bone

0002644

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

Cause

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.

Diagnosis

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]

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.

Treatment

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

Related diseases

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.

Learn more

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.

References

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.
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.
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.
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.
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.
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/.

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Infancy

Q78.8

Autosomal dominant A pathogenic variant in only one gene copy in each cell is sufficient to cause an autosomal dominant disease.

Autosomal recessive Pathogenic variants in both copies of each gene of the chromosome are needed to cause an autosomal recessive disease and observe the mutant phenotype.

X-linked dominant X-linked dominant inheritance, sometimes referred to as X-linked dominance, is a mode of genetic inheritance by which a dominant gene is carried on the X chromosome.

X-linked recessive Pathogenic variants in both copies of a gene on the X chromosome cause an X-linked recessive disorder.

Mitochondrial or multigenic Mitochondrial genetic disorders can be caused by changes (mutations) in either the mitochondrial DNA or nuclear DNA that lead to dysfunction of the mitochondria and inadequate production of energy.

Multigenic or multifactor Inheritance involving many factors, of which at least one is genetic but none is of overwhelming importance, as in the causation of a disease by multiple genetic and environmental factors.

Not applicable

Other names (AKA)

Categories

Summary

Symptoms

Cause

Diagnosis

Testing Resources

Treatment

Related diseases

Learn more

Where to Start

In-Depth Information

References

X-linked
dominant X-linked dominant inheritance, sometimes referred to as X-linked dominance, is a mode of genetic inheritance by which a dominant gene is carried on the X chromosome.

X-linked
recessive Pathogenic variants in both copies of a gene on the X chromosome cause an X-linked recessive disorder.