A particular type of syndrome where damaged soft tissues regrow as bone. Thus sufferers are imprisoned by their skeleton.
One of the rarest genetic diseases and a connective tissue disorder with autosomal dominant inheritance. It is characterized by abnormal ectopic calcification of tendons, ligaments, skeletal muscles, excluding the smooth muscle—the deformity results in restricted joint movements at the corresponding sites and respiratory failure and pulmonary infections.The most common cause of Stoneman syndrome is a mutation of the gene ACVR1. It leads to defects in the body’s repair mechanism. It is an autosomal dominant disorder. Thus, a child of an affected heterozygous parent and an unaffected one has a 50% probability of being affected. Two affected individuals can produce unaffected children. Two unaffected individuals can produce an affected offspring due to the mutation of the gene. The protein that causes ossification is deactivated in standard cases after a fetus’s bone formation, but in Stoneman’s syndrome, the reverse happens. This process leads to the formation of lymphocytes containing Bone Morphogenetic Protein4(BMP4), which contributes to the development of the skeleton in the normal embryo. The ACVR1 gene encodes the bone morphogenic protein (BMP) receptor mutated in this syndrome. This genetic result concludes in an overgrowth of bone and cartilage and the fusion of the joints.
DNA sequencing electropherograms of a typical FOP patient being compared to the other two patients. The unsure base “N” indicates site heterozygous for the mutation and wild-type gene.
New bone formation takes place, replacing the degenerated tissues. This further leads to the formation of a secondary skeleton, causing restricted mobility of the person’s limbs. The only difference between this bone and the original one is the wrong location.
Usually congenital, children are born with malformations of the big toes, a missing joint, or any kind of lump in the minor joints. The first flare-up which usually leads to this deformity occurs in the age group of below 10years. The growth starts mainly in the upper portion progressing downwards. The ossification of fibrous tissues takes place, which may be sudden or due to traumatic onset. It begins specifically in the dorsal, axial, cranial, and proximal regions of the body. Later the disease progresses in the ventral, appendicular, caudal and distal regions. This bone growth occurring during the flare-up phase results in reduced mobility of affected joints. It also results in knee or hip mobilization causing the patient’s inability to walk. This condition also includes the formation of additional bones. In children, it’s often noticed in the neck, later the shoulders, arms, chest, and concluding at the feet. If this extra bone formation occurs at the ribcage, it will result in restricted respiratory movements due to limited lung expansion and ribcage.
As this disorder has characteristic findings, it can be easily diagnosed with plain radiographs. It presents with signs of the shortened great toe with a malformed distal first metatarsal and a missing or abnormal first phalanx with or without interphalangeal joint.It is clinically measured by elevated alkaline phosphatase levels and bone-specific alkaline phosphatase.
AP and lateral radiographs of the neck reveal heterotopic ossification (blue arrow) in the posterior aspect of soft tissues of the neck. The cervical vertebral bodies and the posterior elements are normal in this case. The patient had restriction of neck movements.
Posteroanterior chest radiograph reveals heterotopic ossification (blue arrows) in soft tissues of chest wall and abdomen.
Being one of the rarest diseases, there’s no specific cure to date. Some research includes steroids as the treatment but has not yet been confirmed. If the bone is surgically extracted may result in explosive growth of new bones. Anesthesia in surgery may encounter difficulties with changes in the heart’s electrical conduction system, pulmonary diseases, or intubation. Activities including any soft tissue injury or soft tissues should be avoided, leading to this deformity formation.
Fibrodysplasia ossificans progressiva or Stoneman’s syndrome is a rare and disabling disorder; if misdiagnosed, it can lead to unnecessary surgical intervention and high-risk results of early disability. Thus early treatment and measures are needed to prevent further complications. Awareness of this rare disease should be done to reduce the risks of this rare condition.
Pratiksha Baliga, Youth Medical Journal 2022
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