.

Pyle’s disease is a rare familial metaphyseal dysplasia disorder with few reports worldwide(1-7). This paper presents a case report, review of literature, possible treatment options for Pyle’s disease and discusses the differential diagnosis for Erlenmeyer flask deformity.

A 12-year-old male child born to a third-degree consanguineous couple was referred to our genetic clinic as a case of suspected Gaucher’s disease. He presented with increasing wasting of lower limbs for 6 months. There was history of fracture of right forearm after trivial trauma. There was no history of bone or joint pains, jaundice, blood transfusion or developmental delay. There was no family history of similar problem. His weight was 28 Kg (at 10th centile NCHS) and height was 138 cm (between 10th and 25th centile NCHS). He had hypotelorism, round face, misaligned teeth and small chin. He also had widening of bones of the forearm along with genu valgum and wasting of legs. There was no scoliosis, anemia, or hepatosplenomegaly. Examina-tion of the parents was normal. Investigations revealed normal hematological, renal and hepatic parameters. Skeletal survey showed expansion of cortical marrow in bilateral distal femora (Fig. 1) and proximal tibiae (Fig. 2) suggestive of Erlen-meyer flask deformity. There was mild expansion of lower end of ulna. Multiple growth arrest lines, diffuse osteopenia and bowing of the bilateral tibiae was also seen (Fig. 2). X-ray of the dorsolumbar spine revealed platyspondyly. X-ray skull and chest were normal. Bone densitometry was suggestive of osteoporosis (z score-5.3). Based on clinical features and radiological findings, we made a diagnosis of Pyle metaphyseal dysplasia.

Fig. 1. X-ray of lower thigh lateral view showing Erlenmeyer flask deformity in distal femora. Note diffuse osteopenia.		Fig. 2. X-ray of upper leg AP view showing Erlenmeyer flask deformity in bilateral proximal tibia. Note multiple growth arrest lines and bowing of the tibia.

Pyle metaphyseal dysplasia has peculiar radiological findings with relatively unremarkable phenotypic features. It is characterized by defect in metaphyseal remodeling that leads to grossly widened metaphyses of long bones with marked cortical thinning and osteoporosis (Erlenmeyer-flask deformity) especially in the distal end of femur and proximal tibia. Proximal two-thirds of humerus and distal two-thirds of radius and ulna may show similar changes. Similar but less striking changes are seen in other distal long bones, distal metacarpals and proximal phalanges. Spinal involvement varies from moderate platyspondyly to biconcave lens appearance of the vertebral bodies(3,4). Jaw involvement has also been documented(5). Skeletal survey of obligate heterozygotes may show minor skeletal changes. Along with these roentgenographic changes, there may be few clinical signs and symptoms like muscle weakness, joint pain, genu valgum, scoliosis, and limited extension of elbow. Temporary asymmetrical tibial epiphysiodesis or bilateral osteotomies can correct the progressive genu valgum not only by provoking the momentary arrest of growth in the growth cartilage on the internal tibial aspect, but also by allowing for bone remodeling in the tibial metaphysis(6,7).

Other differential diagnoses of Erlenmeyer flask deformity are craniotubular dysplasias including craniometaphyseal and craniodiaphyseal dysplasia, Gaucher disease, osteopetrosis, thalassemia and Niemann Pick disease. Absence of cranial involvement excludes first three diagnoses in our patient. Moreover, our patient did not have anemia, jaundice, hepatosplenomegaly, increased bone density or any history of blood transfusion ruling out the latter four possibilities also.

Contributors: NG, MK: Preparing and reviewing the literature; and CJD, AKG-Radiological description.

Funding: None.

Competing interests: None stated.