Clinical History
45-year-old Caucasian male patient seen in the clinic since childhood.
Imaging Findings
Dysmorphic pattern of lower thoracic and lumbar vertebra with anterior and posterior wedge deformities at upper lumbar segments and multilevel platyspondylia.
Pattern of posterior vertebral body wedging at L1 segment, complementary anterior vertebral body L2 wedging and complementary upward deformity of the L3 vertebral body matching the anterior wedging of L2. Posterior disc osteophyte complex at the L1-L2 endplates abutting the ventral surface of the thecal sac immediately below the conus medullaris tip. There is ligamentum flavum posteriorly at the T12-L1 level abutting the posterior surface of the conus medullaris.
Discussion
Mucopolysaccharidosis (MPS) IV, also known as Morquio syndrome is an autosomal recessive disease, which presents a lysosomal storage disorder.
This type of MPS results from deficiency of the enzyme N-acetylgalactosamine-6-sulfate sulfatase a lysosomal enzyme responsible for the degradation of keratan sulfate and chondroitin-6-sulfate which accumulates in various tissues including cartilage, the nucleus pulposus of the intervertebral disc and cornea. MPS IV has progressive multisystem dysfunction and impaired functional capacity. [1]
Morquio syndrome has shown a challenge in the diagnosis of young patients due to the lack of knowledge about the disease and its broad clinical spectrum. The clinical manifestations appear at 1-3 years of age, the orthopaedic type being the most evident.
One of the first syndromic manifestations observed is a progressive deformity in the chest known as pigeon chest. This can be seen in plain radiography and CT as an increased AP chest diameter, wide ribs, and anterior sternal bowing. Major joint involvement is also evident, valgus knees are as well one of the first clinical manifestations. The limitation to lift shoulders and raise the arms above the head, wrist deformity and a worsening hand function are present later on towards 5 or 6 years of age. Short femoral necks and severe degenerative changes of the hip joints can be observed in a standing anteroposterior XR view of the pelvis
Platyspondyly is a radiographic feature and refers to flattened shape vertebral bodies with reduced distance between the endplates. Generalised or universal platyspondyly is a radiological sign relatively specific in MPS IV [1, 2, 3]. Platyspondyly is found less frequently in Gaucher disease, metatrophic dysplasia, osteogenesis imperfecta and Kniest dysplasia.
Growth retardation is seen in these type of patients due to the severe skeletal changes. Gait can become abnormal because of genu valgum, which is a peripheral musculoskeletal radiographic feature. Hypoplasia of the odontoid with a mild narrowing of the spinal canal and cord compression at the level of C2-C3 is a critical feature that should be identified in patients with Morquio syndrome. [1, 3, 4]
Before considering the pathophysiology of the disease and still nowadays, the treatment for MPS IV was based on symptom-based medications, physical therapy, and surgery. However, there is an ongoing investigation regarding enzyme replacement therapy (ERT) and haematopoietic stem cell transplantation (HSCT). Nonetheless, HSCT has shown to be very limited; therefore, more data would be necessary to prove its efficacy. [5]
Differential Diagnosis List
Morquio syndrome
Gaucher disease
Metatrophic dysplasia
Osteogenesis imperfecta
Kniest syndrome
