Genetically transmitted malformative syndrome affecting
the connective tissue system. It is characterized by malformed big toes that
are often monophalangic, mild mental retardation, and intermittently
progressive ectopic ossification.
Myositis Ossificans; Münchmeyer Disease.
Incidence is 1:2,000,000 live births and seems to affect
both genders equally.
Autosomal dominant. Gene map locus is
Results from overexpression of a potent
bone-inducing morphogen (bone morphogenetic protein 4) in lymphocytes
that is responsible for ectopic osteogenesis.
Mainly clinical, based on the presence of new bone
formation in the soft tissue. There is also an increase in alkaline
phosphatase during active phase of the disease. Diagnosis established by
molecular biology studies (increased levels of bone morphogenetic protein 4
and its mRNA).
Symptoms usually appear around 6 years of age and
consist of cartilaginous and osteoid transformation of connective tissue.
This ectopic bone formation leads to skeletal muscle mass displacement and
serious limitation of joint movement, mainly in the elbow, hip, and knee.
There is a characteristic hallux deformity, which consists of shortened and
angulated halluces with associated brachymesodactyly. Cervical spine
involvement is common, with varying degrees of cervical fusion and the
possibility of atlantoaxial subluxation. Temporomandibular joint involvement
may occur. Muscles of the face, larynx, eyes, anterior abdominal wall,
diaphragm, and heart usually escape involvement. Finally, limitation of rib
movement may lead to a restrictive, shallow type of breathing but rarely to
respiratory failure, although pneumonia is a common complication. ST-segment
changes and right bundle branch block are however often seen.
Obtain an ECG and pulmonary function
testing. Also obtain baseline alkaline phosphatase level. Cervical spine
radiography to rule out atlantoaxial subluxation should be done
Because of the temporomandibular and
atlantoaxial involvement, direct laryngoscopy may be difficult and
fiberoptic tracheal intubation may be wise. Positioning of the patient on
the operating room table might be more problematic because of the joint
limitations. Successful execution of regional techniques may
be impossible because of the ectopic bone formation. Also, local trauma may
induce more ectopic bone formation. General anesthesia is recommended.
A few patients might be taking
corticosteroids and/or warfarin, so steroid coverage may be warranted or
vitamin K for reversal of warfarin in major surgery.
Mahboubi S, Glaser DL, Shore EM, et al: Fibrodysplasia ossificans
progressiva. Pediatr Radiol
Shafritz AB, Shore EM, Gannon FH: Overexpression of an osteogenic morphogen
in fibrodysplasia ossificans progressiva. Lancet
Semonin O, Fontaine K, Daviaud C, et al: Identification of three novel
mutations of the noggin gene in patients with fibrodysplasia ossificans
progressiva. Am J Med Genet