P-22 INSIDIOUS, RARE, AND MIMICKING BONE DISEASE: PROGRESSIVE PSEUDORHEUMATOID DYSPLASIA
Authors: Onur İşler Alperen , İleri Serez , Kara Zeynep , Elçin Yıldız Adalet , Çağlar Ömür , Gürlek Alper 
Published: January 2025

Abstract

Introduction
Progressive pseudorheumatoid dysplasia (PPD) is a rare autosomal recessive skeletal dysplasia that primarily affects joint cartilage, leading to progressive stiffness and enlargement without inflammation. Symptoms typically manifest between ages 3 and 6. Here we report a case of PPD with a prolonged undiagnosed period, despite early symptom onset.

Clinical Case
A 43-year-old female office manager presented with significant joint mobility limitations and walking difficulties. Her medical history revealed that she first sought medical attention at the age of two due to leg deformities, where genu varum was detected and initially treated as rickets with vitamin D supplementation. At ages 7 and 9, the patient underwent limb lengthening and corrective surgeries for bilateral lower extremity deformities. By age 12, worsening gait required assistive devices. At age 33, a right femoral head fracture necessitated prosthesis implantation, followed by a similar procedure on the left hip at age 36. In the last five years, mobility limitations and pain in the left shoulder and knee have increased. Her medical history was otherwise unremarkable, though her parents were noted to be consanguineous. Physical exam revealed 147 cm height and significant scoliosis. Flexion contractures were observed in the proximal and distal interphalangeal joints of both hands, along with significant mobility limitations in the metacarpophalangeal joints, wrists, and elbows, especially in extension. Additionally, there was limited extension in both knees, more severe on the left, and contractures in the left ankle. No signs of arthritis were present. Laboratory results showed a 25-OH Vitamin D level of 17.53 µg/L, leading to replacement therapy initiation. Acute phase reactants were normal. Radiographic imaging (Figure 1) showed osteoporotic bones, platyspondyly, scoliosis, vertebral endplate irregularities, narrowed disc spaces, and peripheral osteophytes in the vertebral column. Furthermore, epiphyseal enlargement, uniform joint space narrowing, irregular joint surfaces, and periarticular osteopenia were observed bilaterally in the shoulders, elbows, knees, ankles, radiocarpal, midcarpal, carpometacarpal, metacarpophalangeal, and interphalangeal joints. Despite these findings, bone mineral density (BMD) of the L1-L4 vertebrae measured 1.337 g/cm² (Z-score: 1.2) via dual-energy X-ray absorptiometry (DEXA). Based on the clinical, laboratory, and imaging findings, a diagnosis of PPD was established, and the patient was referred for physical therapy and rehabilitation.

Conclusion
This case illustrates a patient with PPD, marked by significant involvement of the hand joints, large joints, and spine, accompanied by short stature. Patients with PPD are frequently undiagnosed or misdiagnosed. The absence of inflammatory features is crucial in distinguishing PPD from juvenile idiopathic arthritis. The lack of extraskeletal involvement further characterizes this disease.Figure 1Figure 1a shows osteoporotic bones, platyspondyly, scoliosis, vertebral endplate irregularities, narrowed disc spaces, and peripheral osteophytes in the vertebral column. Figure 1b and 1c show epiphyseal enlargement, uniform joint space narrowing, irregular joint surfaces, and periarticular osteopenia in both knees and hands.