Clinico-radiological findings in Stoneman disease

PRESENTATION AND CLINICAL FEATURES

An 8-year-old boy exhibited a gradually hardening swelling and progressive limitation of movement along his back for the past 6 years. Upon further inquiry, his parents reported noticing deformities and shortened great toes since his early childhood. There was no history of trauma preceding the onset of symptoms, and no similar occurrences were observed in the family. Upon examination, the patient presented with multiple non-tender, firm subcutaneous nodules along the cervical and lumbar spine. Additionally, both feet displayed bilateral hallux valgus with short great toes (Figure 1).

Figure 1.

Clinical image illustrating swelling (indicated by arrows) on the back (a) and bilateral hallux valgus deformity with shortened great toes (b).

1. Which part of the body needs to be imaged?

Answer

1. Radiograph of the spine and feet followed by cross-sectional imaging preferably Computed tomography (CT) (Figures 2 and 3).

Figure 2.

Conventional radiographs of the cervical and dorsolumbar spine illustrate heterotopic calcifications of different sizes and shapes observed in the fascial and intramuscular planes in the neck and dorsolumbar region (indicated by arrows in a, c, d and e). Additionally, bilateral foot radiographs depict a deformed short proximal phalanx of the great toe with the absence of the distal phalanx (b).

Figure 3.

In the sagittal CT scan of the spine, mature multifocal heterotopic ossification is evident (a and b). Axial images of the cervical spine reveal the ossification (c).

2. What is the most likely diagnosis?

Answer

2. Fibrodysplasia ossificans progressiva or stone man disease.

DISCUSSION

Initially documented by a London-based physician in 1736, myositis ossificans progressiva, also recognised as fibrodysplasia ossificans progressiva (FOP) or stone man disease, is an uncommon connective tissue disorder impacting roughly one in every 2 million individuals [1]. It is characterised by abnormal bone formation in soft tissues such as striated muscles, tendons, fasciae, ligaments and subcutaneous tissues. This hereditary condition follows an autosomal dominant pattern, although the majority of cases arise sporadically, affecting individual family members. FOP manifests through the gradual ossification of connective tissue and muscles, accompanied by digital abnormalities. These anomalies include congenital hallux valgus, monophalangic first toe, shortened metacarpals, pseudoexostoses (ossification of ligamentous insertions), microdactyly of the first metacarpal/metatarsal, short great toe and short thumb. Additional common findings encompass neck muscle edema, fusion of C2-C7 facet joints and enlarged vertebrae [2].

The initial presentation involves a pliable, soft-tissue nodule, which later undergoes ossification. Typically, this process initiates from the cranial to caudal regions and dorsally, progressively limiting mobility and resulting in significant disability. Advanced stages may exhibit bony bridging between the axial and appendicular skeleton. Minor injuries, biopsies and intramuscular injections can trigger flare-ups, exacerbating the progression of the disease with increased inflammation. Characteristic findings are evident in plain radiographs, and radiologists have an important role to play in the diagnosis and follow up. Both plain radiographs and CT can contribute to confirming the diagnosis and assessing its extent. Bone scans and magnetic resonance imaging (MRI) may even allow for earlier detection of the lesions [3].

We present an uncommon instance of FOP in an 8-year-old boy, demonstrating distinctive clinical and radiological features. This case exhibited a gradually hardening swelling and progressive limitation of movement along his back for the past 6 years. Upon further inquiry, his parents reported noticing deformities and shortened great toes since his early childhood. There was no history of trauma preceding the onset of symptoms, and no similar occurrences were observed in the family. Upon examination, the patient presented with multiple non-tender, firm subcutaneous nodules along the cervical and lumbar spine. Additionally, both feet displayed bilateral hallux valgus with short great toes.

Plain radiographs were conducted for the chest, cervical, dorsal and lumbar spine, as well as the hands and feet. The results demonstrated the straightening of the cervical spine and elongated ectopic osseous growths in the soft tissues of the spine. Foot radiographs revealed bilateral hallux valgus deformity, a monophalangic great toe and a short first metatarsal (Figure 1).

A CT scan of the entire spine was conducted to assess the extent (Figure 1). Numerous areas of heterotopic ossification, varying in sizes and shapes, were observed in the subcutaneous and intramuscular planes along the back, spanning from the occiput to the pelvis. The largest of these calcifications measured approximately 1 x 1.3 x 12.7 cm, extending from the occipital protuberance to the D2 vertebra. Thin concentric calcifications were noted along the bilateral posterior paraspinal muscles of the back, extending from C2-C7 and T7-T11. Additional ossified areas were identified in the paraspinal muscles at the T8 to T10 levels and in the bilateral gluteal maximus. The cervical vertebrae appeared enlarged with the expansion of the posterior elements, and the facet joints of the C2-C7 vertebrae were fused.

No invasive investigations were conducted in this case, and the patient’s parents were counselled about the condition. Regular clinical evaluations and ongoing patient follow-up were implemented to facilitate rehabilitation and enhance the overall quality of life. Additionally, recommendations for preventive measures and lifestyle adjustments were provided to minimise the risk of injuries to the patient.

Myositis ossificans progressiva/FOP is a rare autosomal dominant disorder characterised by variable expression and complete penetrance. Clinical manifestations include abnormalities in the great toes and thumbs, coupled with the progressive ectopic ossification of soft tissues leading to restricted movement. The disease is caused by a heterozygous mutation in the ACVR1 gene on chromosome 2q24. The heterotopic ossification in soft tissues closely resembles normal bone, and the poorly understood pathogenesis involves the overproduction of bone morphogenetic protein-4 in lesion and lymphocytic cells [4].

Classic FOP is characterised by two primary clinical features: malformation of the great toes and progressive heterotopic ossification following specific spatial patterns. Individuals with FOP typically appear normal at birth, except for consistent malformations in the great toes present in all classically affected cases. In the first decade of life, children with FOP experience painful and inflammatory soft tissue swellings, beginning in the neck with torticollis as the initial symptom. These swellings, intense in nature, typically resolve within days, leaving behind a doughy area that may either completely resolve or ossify over months. Disease progression starts in the neck, extending downward to the thoracic and lumbar regions before involving the limbs, with distinctive anomalies in the cervical spine and other skeletal abnormalities associated with FOP [5]. Extra-articular ankylosis of the temporomandibular joints is common, leading to severe disability and difficulties with eating and oral hygiene. Ultimately, the disease results in the formation of bony bridges between extremities, torso, ribs and the connection between the thorax and pelvis, severely limiting motion. Over time, affected individuals develop rigid bonds, significantly restricting mobility and transforming their once agile bodies into living statues. Conductive hearing impairment is common in FOP, potentially due to ossification in the middle ear [6]. While the lungs are not directly affected, recurrent infections and atelectasis often arise due to limited chest expansion. Ankylosis affecting major joints leads to dependence and confinement to a wheelchair or bed by the second decade of life [7].

Plain radiographs and CT scans are essential for confirming the diagnosis of FOP and evaluating its extent. Characteristic findings on plain films include deformed and shortened great toes, ectopic calcifications within soft tissues, shortened broad femoral necks, pseudo-exostoses and prominent calcaneal spurs. Advanced stages may exhibit osseous bridging between the axial and appendicular skeleton. CT scans accurately locate lesions and provide valuable information about the disease’s extent. Biopsies are discouraged as they may worsen ossification and lead to confusion with bone malignancies. While plain radiographs are the standard imaging, they may miss the early “preosseous” stage of the disease. Other imaging techniques, such as MRI, excel in this phase, with preosseous lesions appearing dark on T1-weighted images and displaying high signal intensity on T2-weighted images. Muscle tissues near preosseous lesions often exhibit high signal intensity on T2-weighted images, potentially due to secondary inflammation or edema. Bone scans with Gallium 67 citrate and Tc-99m diphosphonate can detect FOP activity earlier than X-rays, even before bone formation becomes evident [8].

In dealing with FOP, the rare and variable nature of the condition presents challenges for experimental therapies. Current medical interventions remain supportive, as surgical procedures like joint releases and osteotomies often fail and pose the risk of trauma-induced heterotopic ossification. Various attempts have been made to treat FOP, but no singular, effective treatment has been identified. However, there is hope and an improved quality of life through preventive measures and symptom management. Minimising trauma, avoiding certain activities and practicing protective measures, such as avoiding contact sports and injections, are recommended. Prophylactic measures, including vaccinations, good hygiene practices and a healthy lifestyle, are crucial. Medications like corticosteroids, non-steroidal anti-inflammatory drugs and bisphosphonates have been explored for managing inflammation and pain during flare-ups. While bisphosphonates like etidronate show promise in slowing bone formation, the potential risk of osteomalacia requires careful consideration. Aminobisphosphonates like pamidronate are being investigated for their potency compared to etidronate. Ongoing research continues to explore new and more effective treatment options for FOP [3].

Living with FOP requires a proactive approach focusing on prevention, symptom management and emotional well-being. Support groups, physical therapy and occupational therapy are crucial for enabling individuals with FOP to lead fulfilling lives. The International FOP Association, founded in June 1988, serves to educate patients, doctors and the public about FOP, support medical research and provide a network of communication for patients and their families [9].

FOP, a rare autosomal dominant connective tissue disorder, involves progressive ectopic ossification of soft tissues. Timely diagnosis is essential for genetic counselling and to mitigate trauma, painful flare-ups and disability progression. The condition often exhibits a classic clinical pattern with identifiable radiological findings on plain films and CT scans. Therefore, radiologists and physicians must be familiar with the diagnostic features of this disorder. Early stages can be identified using bone scans or MRI. Trauma prevention remains the primary approach, with a potential role for bisphosphonates and corticosteroids in managing acute flare-ups.

CONFLICTS OF INTEREST

The authors declare no conflict of interest.

FUNDING

None.

ETHICAL APPROVAL

Signed informed consent for participation and publication of medical details was obtained from the parents of this child. Ethics clearance and approval of publication were granted by our institute.