Applied Radiology

PROBLEM:

A ten-day-old male Malawian child was brought to the hospital with swelling in his left knee. The child was apparently in good health, with no evidence for TORCH infections. His parents brought him to the radiology department, and films of both knees were taken in AP projection. The clinical impression was congenital syphilis. However, no significant radiographic findings were noticed in favor of this diagnosis, and VDRL was negative. Additional views of the chest, pelvis, ankles, wrists, elbows, and the skull were obtained. What is the most likely diagnosis? ³⁸

ANSWER:

Metaphyseal dysostosis

FINDINGS:

Radiological changes were noticed predominantly in the metaphyses of the long bones. There were no signs of periosteal reaction, and epiphyses were unaffected. The trunk and skull did not show any obvious abnormal radiological findings.

An abdominal and cardiac ultrasound scan was performed, though no significant cardiac or visceral anomaly was found.

Later, a blood and synovial fluid culture reported isolation of staphylococcus aureue and a diagnosis of septic arthritis of the knee joint was established. The patient responded very well to cloxacillin given intravenously for seven days.

Both parents were normal and healthy. We did not find any history of congenital anomalies in the family.

DISCUSSION:

Metaphyseal dysostosis was first described by Jansen in 1934. Subsequently, its meaning expanded to include all congenital dysostotic bone disorders with major radiological manifestations at the metaphyses. Metaphyseal dysplasia, metaphyseal dysostosis, and metaphyseal chondrodysplasia are all synonymous. Classification remains controversial and sometimes becomes complicated by patients who, besides having a classical metaphyseal dysplasia, later develop changes elsewhere. As a rule of thumb, though, the spine, diaphyses, and epiphyses are unaffected in this group of patients.

Because of variable etiology, as well as the finding of graduation in manifestations, much confusion has centered around acceptable methods of classification for this group of disorders. Some common and well known groups follow:

Jansen's metaphyseal dysplasia A rare form with a striking clinical and radiological picture. Few cases have been seen in the perinatal period or in early infancy when radiological manifestations are pronounced while clinical signs are mild or absent. One particular manifestation, grossly irregular mineralization, is seen in the metaphyses of tubular bones. The differential diagnosis in very early life includes hypophosphatasia and hyperparathyroidism, both of which can be evaluated by appropriate laboratory examination. Later the condition can be confused with rickets, and occasionally with enchondromatosis. Transmission is by autosomal dominant inheritance.

Schmid type -A milder and most common form of the disorder, it is characterized by moderate but progressive shortening of stature, with bowed legs and a waddling gait. The metaphyses of the long bones are cupped and resemble rickets. Confusion in diagnosis may be resolved by determination of calcium phosphorus and alkaline phosphatase levels in blood. Genetically, transmission is autosomal dominant inheritance.

Types named after Pena & Vaandrager -These are intermediate forms less severe than Jansen's and more severe than the Schmid type in severity. These sometimes are confused with Ollier disease.

Burke type -Metaphyseal dysplasia associated with pancreatic insufficiency and neutropenia.

McKusick type -This is synonymous with cartilage hair hypoplasia. It is a syndrome which occurs in Amish families consisting of metaphyseal lesions, dwarfism, and sparse hair. Causes of this bone disorder are variable and uncertain; some suggest an immune defect is the cause, while others are of the opinion that it is an intrinsic bone disorder.

Prepared by R. Khare, MBBS, MD, Senior Lecturer and Head of Radiology, College of Medicine, Chichiri, Blantyre, Malawi, and David J. Sartoris, Professor of Radiology, University of California, San Diego, CA.