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  • 🐴 Rare Case: Congenital Coffin Joint Dysplasia Diagnosed in a 3-Month-Old Friesian Foal

🐴 Rare Case: Congenital Coffin Joint Dysplasia Diagnosed in a 3-Month-Old Friesian Foal

VRU 2025

Author

Obi Veterinary Education
November 23, 2025

Emmie J. M. Giessen, Emanuel K. L. Stas, Guy C. M. Grinwis, Stefanie Veraa

Background

A 3-month-old Friesian colt presented with severe, progressive distal limb lameness affecting two limbs. Early onset, multifocal lesions, and rapid progression suggested a developmental or congenital etiology. The study aimed to characterize the imaging and histopathologic features of this rare distal interphalangeal joint (DIPJ) disorder and explore possible developmental mechanisms.

Methods

Comprehensive diagnostic workup included radiography of the distal limbs, followed by postmortem full-body computed tomography (CT) and histopathologic examination. The right forelimb and left hindlimb showed the most significant clinical and radiologic changes. Additional macroscopic and microscopic analyses were performed on the navicular bones and distal phalanges. All procedures were conducted postmortem with owner consent.

Results

Radiographs revealed focal osteolysis and irregular bony proliferation at the palmar/plantar margin of the distal phalanx adjacent to the navicular bone. Postmortem CT identified bilateral, focal, severe osteolytic and osteoproliferative changes confined to the distal navicular bone and proximal distal phalanx, causing deformity, joint space narrowing, and partial bony fusion. Multiple additional small osteochondral defects were observed in other joints. Histopathology showed irregular articular surfaces, fibrous tissue infiltration, trabecular thickening, and secondary osteosclerosis and myelofibrosis, consistent with advanced focal joint disease but without an identifiable primary cause.

Limitations

This single case lacked longitudinal follow-up and histopathologic assessment of all affected joints, which limits definitive differentiation between osteochondrosis, vascular disturbance, and congenital dysplasia. The absence of genetic or vascular studies precludes firm etiological conclusions.

Conclusions

The findings indicate a unique case of congenital partial fusion of the navicular bone and distal phalanx with associated DIPJ dysplasia and multifocal osteochondral developmental lesions. The disease likely resulted from abnormal joint development, possibly exacerbated by localized vascular disruption or mechanical stress. Full-body CT proved critical in delineating lesion distribution and should be considered for similar cases of multilimb lameness in young horses.

Multiplanar reconstruction (MPR) fan beam CT images with a bone algorithm of the distal limb. (A) Parasagittal and (B) dorsal plane of the left hind limb, lateral is to the right. Marked subchondral hypoattenuating bone lesions surrounded by a hyperattenuating area (asterisk) are visible at the level of the lateral articulation site of the navicular bone and the distal phalanx. Small, well-defined, tubular hypoattenuating structures within the distal phalanx are visible as focal round regions in (B), likely representing vascular channels. There is an altered shape and elongation of the distal navicular bone and proximal distal phalanx, resulting in focal deformation and narrowing of the plantar joint space (arrow). (C) Parasagittal plane of the right front leg shows similar changes compared with the left hind (A), with a small intra-articular mineral body. (D) Parasagittal plane of the left front limb at the same level as (C), showing normal morphology.

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