Pyle Disease

Inherited bone dysplasia affecting the enchondral growth of long bones, which results in failure of modeling and causes increased circumference of the ends of the shafts.

Pyle Metaphyseal Dysplasia; Familial Metaphyseal Dysplasia. If the cranial features are significant, the disease is also called craniometaphyseal dysplasia.

NB: Metaphyseal dysplasia and metaphyseal chondrodysplasia are not the same disease.

First described by E. Pyle, an American orthopedic surgeon.

About 25 cases have been reported.

Autosomal recessive.

The mechanism or cause remain unknown; however, abnormal tubulation of the bone may play a role.

Made by clinical features and radiographic studies. Symmetrical expansion of the metaphyses of long bones results in the so-called “Erlenmeyer flask deformity,” describing the flaring of long bones (mainly of distal femur and proximal tibia) in combination with cortical thinning in affected areas. This sign is typical, but not pathognomonic, because it can also be seen in osteopetrosis, Niemann-Pick, and Gaucher diseases. Osteoporosis of the long bones with an increased risk for fractures is common.

The patient may be clinically asymptomatic. The patients are almost always tall as a result of increased limb length (especially femur and tibia). The most frequent clinical feature is genu valgum, which is usually mild but may predispose to fractures. The elbows may not fully extend, the proximal humerus is abnormally wide, as are the distal radius and ulna. The widening of the lower end of the femurs may be palpable. There is a gross defect in metaphyseal modeling. Radiologic examination of the spine may reveal platyspondyly, which could be attributed to either the same defect in modeling seen in the metaphyses of the long bones or to pathological fractures as a result of osteoporosis. Scoliosis has been reported in some patients. The head is enlarged with diffuse hyperostosis of the entire cranial vault, bony encroachment on the cranial foramina (potentially resulting in nerve compression with visual and hearing impairment/loss), absent or poorly pneumatized paranasal sinus, significantly thickened bone in the area of the glabella with hypertelorism, and often obstructed nasal breathing (breathing difficulties during upper airway infections have been described). Inconsistently, the presence of deciduous teeth is prolonged with marked cavities and prognathia may be present. Intelligence and general health are normal.

Assess airway and loose teeth. Visual and hearing impairment could make communication difficult. Sedative and anxiolytic premedication, as well as the presence of the primary caregiver, for induction could be helpful.

Airway management could be difficult secondary to the potentially grotesque facial features. Careful positioning is recommended because of an increased risk for fractures secondary to osteoporosis.

There are no specific pharmacological implications.

Niemann-Pick Disease: Lysosomal storage disorder caused by a defect in sphingolipid metabolism and involving brain and/or viscera.

Gaucher Disease: Most common form of inherited lipid storage disease, particularly common in Ashkenazi Jewish people (Eastern European ancestry). Accumulation of glucocerebrosides (derived from RBCs) in many tissues, especially the macrophages in the bone marrow, resulting in impairment of their function.

Osteopetrosis: A heterogenous genetic disorder resulting in increased bone mass as a result of defective bone resorption. Depending on the mode of inheritance, its course can be either uniformly fatal with pancytopenia, recurrent pathological fractures, blindness, and other neurological symptoms, or exist in a much milder form with later manifestation and favorable prognosis.

Metaphyseal Chondrodysplasia, Jansen Type, Metaphyseal Chondrodysplasia, McKusick Type, Metaphyseal Chondrodysplasia, Schmid Type: A heterogenous group of moderate to severe dwarfism with joint dysfunction and in some forms hypercalcemia.