Pyle syndrome is a skeletal dysplasia that particularly affects the metaphyses of the long bones. The cause has not yet been determined, but probably corresponds to an autosomal recessive mutation. Many of the patients are asymptomatic for life and do not require further treatment in this case.
What is Pyle syndrome?
Skeletal dysplasias involve a congenital disorder of bone and cartilage tissue. Metaphyseal dysplasias form one group of skeletal dysplasias. These are congenital disorders that particularly affect the tissues of the metaphysis, the section of long bones between the shaft and the epiphysis. Pyle syndrome is a metaphyseal skeletal dysplasia in which the metaphyses of the long tubular bones show distension. The rare hereditary disease was first described in 1931, and the U.S. orthopedist Edwin Pyle is considered the first describer of metaphyseal dysplasia. The frequency of the disease is reported to be significantly less than one case per 1000,000 people. Since Pyle’s initial description, only about 30 cases have been documented. For this reason, Pyle syndrome has not yet been conclusively investigated. Since many patients do not show any symptoms, the diagnoses are often incidental findings. Because of the asymptomatic nature of the disease, the incidence of unreported cases is probably much higher than the reported prevalence.
Causes
Pyle syndrome is associated with familial clustering. Daniel, in particular, had presented a case study in 1960 that suggests a genetic basis for the syndrome and seems to argue for the heritability of skeletal dysplasia. Bakwin and Krida documented a case of affected siblings as early as 1937. A similar case was described by Hermel in 1953 and Feld in 1955, and Komins documented a particularly significant familial case of Pyle syndrome in 1954 involving the mother and maternal uncle in addition to a mixed-sex sibling. Beighton, meanwhile, reported 20 cases in 1987, seven of which involved parents with no abnormalities. Based on these case reports, scientists have now agreed on an autosomal recessive inheritance for Pyle syndrome. Presumably, a mutation underlies the abnormalities. To date, however, the causative gene has not been pinpointed.
Symptoms, complaints, and signs
Patients with Pyle syndrome often suffer from an axial deviation between the upper and lower legs that resembles a malalignment of the knees. In most cases, the patient’s head is not affected by skeletal malformations. Only in isolated cases is there a slight hyperstosis of the skull in the sense of a thickening of the cranial bones. In many cases there are stretching inhibitions in the area of the elbows. In the area of the clavicles and ribs there are also characteristic distensions. The metaphyses of the affected persons are often widened. The anomalies of the bones promote abnormally frequent fractures in individual cases. In all cases documented so far, without exception, the patients enjoyed excellent health apart from the skeletal dysplasias. Constrictions of the foramina in the cranial region have not been observed in a single case. Typically, patients are asymptomatic, so the diagnosis is generally made by incidental finding.
Diagnosis and course of the disease
The diagnosis of Pyle syndrome is made by imaging techniques. Radiographs show landmark changes such as Erlenmeyer flask-like distention, which corresponds to widening of the metaphyses without cupulation. The anomalies primarily affect the long tubular bones and extend into the diaphysis on these bones. On the short tubular bones, the changes are less obvious. Apart from these criteria, platyspondyly in the sense of knee malalignment may be indicative of Pyle syndrome. The syndrome must be differentiated from other diseases in the context of which an Erlenmeyer deformity can occur, for example from the autosomal-dominant inherited type Braun-Tinschert of metaphyseal dysplasia. The mode of inheritance is a differentiation criterion in this case.
Complications
In most cases, Pyle syndrome results in malalignment of the knees. This malalignment thus also leads to movement restrictions and thus to difficulties and complications in the daily life of the affected person.In some cases, patients are thus also dependent on the help of other people in everyday life. The bones in the skull can also thicken. In many cases, those affected can no longer straighten their knee properly. However, the symptoms usually occur in a very mild form, so that the everyday life of most patients is not restricted by the disease. For this reason, treatment of Pyle’s syndrome is not necessary in every case. As a rule, however, arthrosis must be prevented so that further complaints do not occur. Especially in children, a complication-free development must be guaranteed. In severe cases, those affected are dependent on the use of prostheses. There are no particular complications and the disease usually progresses positively. The life expectancy of affected individuals is also not affected by Pyle syndrome.
When should one go to the doctor?
Since there is no self-healing in Pyle syndrome and the symptoms usually significantly complicate the daily life of the affected person, a doctor should be consulted immediately at the first signs of the syndrome. Since it is a genetic disease, it cannot be treated completely or causally. Therefore, only a purely symptomatic treatment is available to the affected person. The doctor should be consulted in the case of Pyle syndrome if the affected person suffers from movement restrictions or stretching inhibitions, which can make everyday life significantly more difficult. The bones show significant abnormalities, so that even ordinary movement of the patient is usually not possible. In most cases, however, Pyle syndrome is diagnosed only by routine examination, so early investigation usually does not take place. The syndrome is then treated with the help of various surgeries and without complications.
Treatment and therapy
In most cases, patients with Pyle syndrome do not continue to suffer from their abnormalities. As long as the metaphyseal changes do not cause any symptoms, further therapy is not necessary. Only when the first impairments become apparent is therapeutic intervention indicated. Since knee deformities can promote osteoarthritis in the course of time, an epiphysiodesis is ideally performed before the end of growth if the deformity is significant. In this procedure, the growth plates of the bones are closed on one side so that the residual growth on the other side can compensate for the malposition. After growth completion, correction of the malposition can take place by means of realignment osteotomies over the articular cartilage on the femur and then corresponds to the surgical procedure of a supracondylar femoral osteotomy. A different approach is offered with the intervention below the tibial plateau, which corresponds to a high tibial osteotomy. If the deformity has already led to osteoarthritis, no correction is performed, but a knee joint prosthesis is inserted. Orthopedic correction may also be required at the elbows if stretch inhibition causes severe impairments in the patient’s daily life. However, since affected individuals often remain asymptomatic throughout their lives, interventions are actually required only in isolated cases.
Prevention
To date, the causes of Pyle syndrome can only be speculated. Therefore, no measures are yet available to prevent the disease. Because the syndrome has a hereditary basis, the most affected individuals can do is avoid passing it on by deciding not to have their own children. However, because the syndrome is not a disease with severe impairments, such a radical decision is not absolutely necessary. The purpose of follow-up care in Pyle syndrome is to continue therapeutic treatments and measures. Therefore, the aftercare treatments are usually aimed at maintaining the mobility of the affected person’s musculoskeletal system. In the majority of cases, the affected persons are no longer able to properly straighten their knee. In these mild cases of disease, further medical examinations are often no longer necessary. This is because neither complications nor difficulties are to be expected in the everyday life of the affected person. In principle, however, measures should be taken to prevent osteoarthritis of the knee (gradual wear and tear of the cartilage in the knee joint).A low-fat and balanced diet as well as a joint-friendly behavior of the affected person can help here. Overweight should also be avoided. In the case of children affected by Pyle syndrome, follow-up care must guarantee the complication-free development of the musculoskeletal system. In order to be able to treat an aggravation of the malposition of the knee in time, clinical or outpatient X-rays should be taken regularly (at least every six months) and evaluated accordingly by specialists. Despite medical monitoring, Pyle’s syndrome can still lead to severe movement restrictions. In individual cases, prostheses may have to be used to maintain mobility. Aftercare then focuses on dealing with the disease and the prostheses in everyday life. In general, however, Pyle’s syndrome does not reduce the life expectancy of those affected. The object of aftercare in Pyle syndrome is the continuation of therapeutic treatments and measures. Therefore, the follow-up treatments are usually aimed at maintaining the mobility of the affected person’s musculoskeletal system. In the majority of cases, the affected persons are no longer able to properly straighten their knee. In these mild cases of disease, further medical examinations are often no longer necessary. This is because neither complications nor difficulties are to be expected in the everyday life of the affected person. In principle, however, measures should be taken to prevent osteoarthritis of the knee (gradual wear and tear of the cartilage in the knee joint). A low-fat and balanced diet as well as a joint-friendly behavior of the affected person can help here. Excess weight should also be avoided. In the case of children affected by Pyle’s syndrome, follow-up care must guarantee the complication-free development of the musculoskeletal system. In order to be able to treat an aggravation of the malposition of the knee in time, clinical or outpatient X-rays should be taken regularly (at least every six months) and evaluated accordingly by specialists. Despite medical monitoring, Pyle’s syndrome can still lead to severe movement restrictions. In individual cases, prostheses may have to be used to maintain mobility. Aftercare then focuses on dealing with the disease and the prostheses in everyday life. In general, however, Pyle syndrome does not reduce the life expectancy of those affected.
Aftercare
The object of follow-up care in Pyle syndrome is the continuation of therapeutic treatments and measures. Follow-up treatments are usually aimed at maintaining the mobility of the affected person’s musculoskeletal system. In the majority of conditions, sufferers can no longer properly extend their knee. In these mild cases of disease, further medical examinations are often no longer necessary. This is because neither complications nor difficulties are to be expected in the everyday life of the affected person. In principle, however, measures should be taken to prevent osteoarthritis of the knee (gradual wear and tear of the cartilage in the knee joint). A low-fat and balanced diet as well as a joint-friendly behavior of the affected person can help here. Excess weight should also be avoided. In the case of children affected by Pyle’s syndrome, follow-up care must guarantee the complication-free development of the musculoskeletal system. In order to be able to treat an aggravation of the malposition of the knee in time, clinical or outpatient X-rays should be taken regularly (at least every six months) and evaluated accordingly by specialists. Despite medical monitoring, Pyle’s syndrome can still lead to severe movement restrictions. In individual cases, prostheses may have to be used to maintain mobility. Aftercare then focuses on how to deal with the disease and the prostheses in everyday life. In general, however, Pyle syndrome does not reduce the life expectancy of those affected.