Micromelic dysplasia-like syndrome in a captive colony of common marmosets (Callithrix jacchus)

Abstract

Over several years, 0% to 5% of adolescent animals in a captive colony of common marmosets (Callithrix jacchus) showed severely bended arms and legs over several years. The animals showed no pain, discomfort, or altered behavior but were unable to stretch their distal limbs to their full extent. To characterize the lesion morphologically, the bones of 4 affected marmosets were compared macroscopically and radiographically with those of 6 unaffected animals. The deformities were characterized by mid- to distal diaphyseal bending and pronounced shortening of long bones. The morphology and density of other bones including the skull and vertebrae were unaffected. Although vitamin D values were low in a fifth affected marmoset during 10 to 16 mo of age, lesions associated with rickets were not observed. To our knowledge, this report is the first to describe a micromelic dysplasia-like syndrome comprising severe, idiopathic bending and shortening of long bones in a colony of marmosets.

Figure 1.

Radiographs of the macerated scapulae and long bones of an affected and a nonaffected marmoset. On the left are a (A) scapula, (B) humerus, (C) radius and ulna, (D) femur, and (E) tibia and fibula of affected marmoset A1. The corresponding bones of nonaffected marmoset C1 are on the right. Shadows on the pictures are from modeling clay used to fix the bones. All images are craniocaudal views, except for the radius and ulna (C), which are shown in a lateromedial direction. The different bones of each animal originally were all on the same radiograph but were reorganized for clarity. In panel C, the solid line shows how the shortest length (SL) was measured and the dashed line shows how the actual length (AL) was measured. Scale bar, 5 mm.

Figure 2.

The shortest lengths (SL) of the scapula, humerus, radius, ulna, femur, tibia, and fibula of affected marmosets and controls were measured and compared by using the nonparametric Mann–Whitney test (†, P < 0.01; ‡, P < 0.001).

Figure 3.

The actual lengths (AL) of the scapula, humerus, radius, ulna, femur, tibia, and fibula of affected marmosets and controls were measured and compared by using the nonparametric Mann–Whitney test (*, P < 0.05; ‡, P < 0.001).

Figure 4.

The ratios of the shortest length (SL) to the actual length (AL) of the scapula, humerus, radius, ulna, femur, tibia, and fibula of affected and control animals were determined and compared by using the nonparametrical Mann–Whitney test (*, P < 0.05; †, P < 0.01; ‡, P < 0.001).

Figure 5.

Sagittal section of femoral condyl of marmoset A2, demonstrating homogeneous calcification of cancelous bone and subchondral bone cysts. Bar, 200 µm.

Figure 6.

(A) Serum vitamin D and (B) PTH levels of 1 affected (A5) and 7 nonaffected (C7 through C13) marmosets between the ages of 10 and 16 mo.