Pycnodysostosis

Was ist Pycnodysostosis?

It is a rare genetic syndrome that presents with unique facial features, skeletal abnormalities and a hardening of the bones. It is a lysosomal storage disorder and often compared to osteoporosis. There is still a lot that isn’t known about the disease, in terms of its symptoms, and symptoms may vary widely across affected individuals.

The syndrome has currently been reported in 200 people worldwide, but it is possible that the syndrome is under diagnosed.

This syndrome is also known as:
Maroteaux-Lamy pyknodysostosis syndrome Pycd Pyknodysostosis; Pknd

Was Genveränderungen verursachen Pycnodysostosis?


Mutationen im CTSK-Gen verursachen das Syndrom.

Es wird autosomal-rezessiv vererbt. Einige betroffene Personen haben Eltern, die durch Blut verwandt sind, was das Risiko erhöht, dass ein Syndrom in einem autosomal rezessiven Muster vererbt wird.

Was sind die wichtigsten symptome von Pycnodysostosis?

The earliest identified symptoms of the syndrome may include a larger skull than normal. This is caused by the delayed fusing together of the joints of an infant's skull known as sutures.

Unique facial features of the syndrome include a prominent forehead, a pointed nose, a high arched palate, prominent eyes that are blue and a small jaw.

Dental issues are also common. These might include the delayed eruption of baby and permanent teeth. In some instances teeth fail to develop at all.

Bone anomalies include a malformed collarbone and a breakdown of the bone in the tips of fingers and toes. Fingers may also be smaller than normal with missing fingernails. A hardening of the bones is common with the syndrome. This in turn causes fragile bones, leaving affected individuals more susceptible to fractures. These fractures might be caused by injury or appear without being injured.

Respiratory and sleep issues are also possible symptoms. These are often caused by a malformation of the chest triggered by the syndrome.
A short stature and shorter limbs are also associated with the condition.

Possible clinical traits/features:
Bone pain, Blue sclerae, Absent frontal sinuses, Anonychia, Abnormality of the thorax, Abnormality of pelvic girdle bone morphology, Abnormal palate morphology, Carious teeth, Abnormal fingernail morphology, Abnormality of the clavicle, Abnormality of epiphysis morphology, Persistence of primary teeth, Persistent open anterior fontanelle, Osteolysis, Osteolytic defects of the distal phalanges of the hand, Osteomyelitis, Autosomal recessive inheritance, Brachydactyly, Prominent nose, Malar flattening, Anemia, Delayed eruption of teeth, Delayed eruption of primary teeth, Delayed eruption of permanent teeth, Abnormal pattern of respiration, Abnormality of dental morphology, Increased bone mineral density, Micrognathia, Narrow palate, Narrow chest, Splenomegaly, Ridged nail, Frontal bossing, Proptosis, Wormian bones, Spondylolisthesis, Spondylolysis, Recurrent fractures, Scoliosis, Skeletal dysplasia, Hydrocephalus, High forehead, Cognitive impairment, Hepatomegaly, Short stature, Hypodontia, Short toe, Prominent

Wie wird jemand getestet? Pycnodysostosis?

The initial testing for Pycnodysostosis can begin with facial analysis screening, through the FDNA Telehealth telegenetics platform, which can identify the key markers of the syndrome and outline the need for further testing. A consultation with a genetic counselor and then a geneticist will follow.

Based on this clinical consultation with a geneticist, the different options for genetic testing will be shared and consent will be sought for further testing

Medizinische Informationen zu Pycnodysostosis

The cranium is relatively large and this is accentuated by a small face and micrognathia. The sclerae may be blue with exophthalmos. The nose is pinched with anteverted nares and the palate is high and grooved. The deciduous teeth may persist giving a double row of teeth. The shoulders are narrow and there may be a thoracic kyphosis and lumbar lordosis. The tips of the fingers are short and bulbous, the nails thin and hypoplastic, and the skin over the dorsum of the hands wrinkled. Radiographs reveal generalised increased bone density, multiple wormian bones, osteolysis of the distal phalanges and partial aplasia of the the distal ends of the clavicles. Characteristically the mandibular angles are absent. The main problems are short stature, dental caries, fractures of the bones and osteomyelitis. Le Bouedec et al., (1995) reported two sibs with radiological features of the condition, one of whom had a leukoerythroblastic anaemia with thrombocytopenia and hepatosplenomegaly. Mocan et al., (1997) reported a case with haemanigoma of the skull, but it was not obvious form the case report or radiographs published where this haemangioma was. Soliman et al., (1996) describe a good response to growth hormone treatment in 5 out of 6 cases. Darcan et al., (1996) reported a case with growth hormone deficiency. A patient reported by Cortisse developed an osteosarcoma.
Wada et al., (2015) reported a case with spinal canal stenosis secondary to ossification of the longitudinal ligament.
GENETICS
Gelb et al., (1995) and Polymeropoulos et al., (1995) mapped the gene to 1q21. Gelb et al., (1996) found mutations in the cathepsin K gene which codes for a cysteine protease expressed in osteoclasts. A further nonsense mutation was reported by Johnson et al., (1996).
Gelb et al., (1998) reported a patient with pyknodysostosis who was found to have paternal uniparental disomy for chromosome 1 due to a meiosis II nondisjunction event. He was of normal intelligence and just had features of pyknodysostosis.Ozdemir et al., (2013) reported 3 cases in 2 families all with a novel mutation in exon 4 and with a mild phenotype. Six cases inluding a sib-pair and their 2 cousins were reported by Valdes-Flores et al., (2014). Two of their patients were not short.

* This information is courtesy of the L M D.
If you find a mistake or would like to contribute additional information, please email us at: [email protected]

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