Metaphyseal chondrodysplasia Schmid type

Definition

Metaphyseal chondrodysplasia, Schmid type (MCDS) is a type of skeletal disorder in which there is abnormal bone formation at the end of the long bones (metaphyses).

cause

MCDS is caused by a mutation in one of the collagen genes known as COL10A1.

Inheritance

Autosomal dominant pattern, a 50/50 chance.

The mutation may be inherited from a parent or may happen for the first time in an affected individual.The MCDS mutation is passed on in an autosomal dominant manner.

Signs and symptoms

• Symptoms include short stature with abnormally short arms and legs (short-limbed dwarfism) and bowed legs (genu varum).
• Additional signs and symptoms may include lumbar lordosis, leg pain, joint pain, hip deformities, and an outward flaring of the bones of the lower rib cage. As a result of the hip and leg findings, individuals with this condition may have an unusual walk that resembles a waddle.

Clinical presentation

For most diseases, symptoms will vary from person to person. People with the same disease may not have all the symptoms listed.

80%-99% of people have these symptoms

• Coxa vara
• Distal femoral metaphyseal abnormality(Abnormality of wide portion of outermost thighbone)
• Limb undergrowth(limb shortening)
• Thick growth plates
• Waddling gait('Waddling' gait)

30%-79% of people have these symptoms

• Abnormalities of the metaphyses of the hand(Abnormality of the wide portion of the hand bone)
• Anterior rib cupping
• Broad proximal phalanges of the hand(Broad innermost finger bones of the hand)
• Disproportionate short-limb short stature(Short limb dwarfism, disproportionate)
• Distal femoral metaphyseal irregularity
• Femoral bowing(Bowed thighbone)
• Flared metaphysis(Flared wide portion of long bone)
• Genu varum(Outward bow-leggedness)
• Hip dysplasia
• Metaphyseal cupping of metacarpals(Cupping of wide portion of long bone of hand)
• Metaphyseal cupping of proximal phalanges
• Osteosclerosis of ribs(Increased bone density in ribs)
• Proximal femoral metaphyseal irregularity
• Short tubular bones of the hand
• Widened proximal tibial metaphyses(Wide innermost wide portion of shankbone bone)

5%-29% of people have these symptoms

• Arthralgia(Joint pain)
• Irregular vertebral endplates
• Lumbar hyperlordosis(Excessive inward curvature of lower spine)
• Obesity(Having too much body fat)
• Platyspondyly(Flattened vertebrae)
• Radial metaphyseal irregularity
• Ulnar metaphyseal irregularity

Diagnosis

• No formal diagnostic criteria for Schmid metaphyseal chondrodysplasia (SMCD) have been established. The diagnosis should be suspected in individuals with the following clinical, laboratory, and radiographic findings.[1].

Clinical findings

• Short-limbed short stature by age two years (in >60%)
• Genu varum (bowed legs) (>60%)
• Waddling gait (>80%)
• Lumbar lordosis by age three to five years
• Normal craniofacies and absence of extraskeletal manifestations

Laboratory findings. Normal serum calcium, phosphate, vitamin D, and alkaline phosphatase

Radiographic findings

• Shortening of the tubular bones (>60%)
• Metaphyseal irregularities of the long bones (e.g., splaying, flaring, cupping) especially the proximal and distal femora (~100%)
• Widening of the growth plates
• Coxa vara (>80%)
• Anterior cupping, sclerosis, and splaying of the ribs (>90%)
• Mild hand involvement including shortening of the tubular bones and metaphyseal cupping of the metacarpals and proximal phalanges (~50%).
• Radiographic phalangeal and metacarpal findings may resolve with age.

The diagnosis of SMCD is established in a proband with characteristic clinical and radiographic features and/or a heterozygous pathogenic variant in COL10A1 identified by molecular genetic testing.

Treatment

• Management of orthopedic complications by orthopedist, physiotherapist, occupational therapist, and pain specialist as indicated.
• Joint-friendly exercise, weight management
• Mobility device as needed
• Corrective osteotomy by guided growth surgery or valgus osteotomy may be considered in late childhood / adolescence in those with progressive or symptomatic varus deformity, significant coxa vara, triangular fragment in the interior femoral neck, or poor or deteriorating function
• Exercise and support from nutritionist to maintain healthy weight
• Psychosocial support
• Environmental or occupational modifications as needed for short stature with recommendations from occupational therapy as needed.[2].

External links

Classification	ICD-10: Q78.5 OMIM: 156500 MeSH: C537352
External resources	Orphanet: 174

NIH genetic and rare disease info

• NIH info on Metaphyseal chondrodysplasia Schmid type

Metaphyseal chondrodysplasia Schmid type is a rare disease.

Metaphyseal chondrodysplasia Schmid type Resources
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