1. Cardiovascular System
One of the most significant post-1996 discoveries has been the extent to which OI damages the heart and vasculature — not merely as a consequence of skeletal deformity, but as a direct expression of defective collagen.
A 2024 systematic review of the literature found that the following
Initially Heart issues were considered to be caused by the malformation of the rib cage through frequent breaks and remodeling, but a study in 2012 demonstrated that this was dated information that no longer applied. This was particularly important because it demonstrated that cardiac and pulmonary damage in OI different types of collagen, and Agt in heart and lung tissue supported a bone-independent vicious cycle of heart dysfunction, including hypertrophy and loss of myocardial matrix integrity. 
PubMed Central
A 2022 study in Frontiers in Endocrinology examining children with OI found that:
- significantly larger values for the main pulmonary artery,
-- left atrial diameter,
left ventricular internal dimension,
as well as lower left ventricular ejection fraction
compared with healthy controls.
Furthermore, cardiovascular abnormalities appeared to correlate directly with COL1A1 mutation and collagen type I defects. ResearchGate
A study of childhood OI published in the European Journal of Pediatrics reported that children with the severe (type III) clinical course showed aortic root dilatation in 28% of cases and increased septal and posterior left ventricular wall thickening. Kidney stones and renal papillary calcifications were also detected in some children. Springer
Most recently, a 2025 expert consensus piece in the Journal of Bone and Mineral Research used a modified Delphi technique to identify clinical characteristics, care recommendations, and research priorities specifically for cardiovascular disease in adults with OI — reflecting how seriously the field now takes this dimension of the condition.
Representative Papers:
Ashournia et al., 2015, systematic review of heart disease in OI.
Verdonk et al., 2024, systematic review of cardiovascular abnormalities in OI.
Folkestad et al., 2025, cardiovascular disease in adults with OI.
Thatcher et al., 2023, aortic valve pathogenesis in oim/oim mice.
2. Respiratory / Pulmonary System
Although OI is primarily described as a bone disorder, the majority of OI mortality and morbidity is caused by respiratory and cardiac conditions, which were historically considered secondary to skeletal deformities. A primary role of the mutant collagen in cardio-respiratory disease was suggested by the Aga2 mouse model research, which found a significant progressive decline in pulmonary function and restrictive pulmonary disease independent of scoliosis in a pediatric OI cohort. PubMed Central
spinal deformity and pulmonary compromise were related,
Restrictive pulmonary disease
rib cage restriction from scoliosis and kyphosis
lung involvement should be monitored proactively rather than reactively.
Representative papers:
Tam et al., 2018, multicenter pulmonary function study in 217 children and adults.
Storoni et al., 2021, review of respiratory failure pathophysiology.
Thiele et al., 2012, cardiopulmonary dysfunction in mouse model and human patients from bone-independent mechanisms.
Dimori et al., 2022, intrinsic lung abnormalities in OI mouse models.
Lenoir et al., 2024, adult cohort lung function study.
3. Auditory System
Hearing loss had long been recognized in OI — Van der Hoeve described it as early as 1918 — but the mechanisms were poorly understood until molecular research allowed the specific collagen pathology in the otic capsule to be characterized.
Hearing loss is commonly found in OI
with prevalence rates ranging from 50 to 92%
It may be conductive, mixed, or sensorineural,
More common by the second or third decade of life
Collagen is the dominant protein in auditory structures
disordered type I collagen in the ear involves both hard and soft tissue
Histopathologic findings in temporal bones from have shown evidence of both
- Pure sensorineural hearing loss is due to cochlear microfractures,
Interestingly, bisphosphonate therapy may possibly delay the onset of hearing loss ScienceDirect, though long-term studies with larger sample sizes are still needed to confirm this.
Representative papers:
Kuurila et al., 2000, hearing loss in children with OI.
Machol et al., 2020, hearing loss in individuals with OI in a large cohort.
Carré et al., 2019, literature review of hearing impairment in OI.
4. Neurological System — Basilar Invagination
One of the most serious and under-recognised extraskeletal complications researched since the 1990s is basilar invagination.
DEFINITION: Basilar invagination is a rare craniocervical junction disorder where the top of the spine (usually the odontoid process of C2) protrudes upward into the base of the skull, known as the foramen magnum. This structural defect compresses the brainstem and spinal cord, causing serious neurological symptoms, including severe headaches, neck weakness, dizziness, and motor issues
BI generally progresses slowly in childhood;
Representative papers:
Arponen et al., 2012, prevalence and natural course of craniocervical junction anomalies.
De Nova-García et al., 2023, severity of OI and cranial base/craniocervical involvement.
5. Dental and Craniofacial System
The abnormal development of craniofacial structures has been documented in all types of OI.
Dentinogenesis imperfecta - is more severe in OI type III, - similar issues seem more prevalant than on average.
dental malocclusion,
missing teeth, and e
ctopic teeth are more common
Representative papers:
Rios et al., 2005, review of dentinogenesis imperfecta in OI.
Prado et al., 2023, dental anomalies beyond classic dentinogenesis imperfecta.
Ventura et al., 2024, comprehensive review of dental abnormalities in OI.
6. Musculoskeletal System Beyond Bone — Muscle Weakness
After 1996, attention turned to the profound muscle involvement in OI, which had previously been attributed simply to inactivity or disuse from fractures.
Research published in International Journal of Molecular Sciences in 2021 specifically examined the impact of intrinsic muscle weakness on muscle-bone crosstalk in OI, showing that the relationship is bidirectional and that weakened muscle further compromises bone development — a feedback loop that purely bone-focused treatments cannot address.
Representative papers:
Veilleux et al., 2015, the functional muscle-bone unit in OI.
Veilleux et al., 2017, review of muscle abnormalities in OI.
Gentry et al., 2010, skeletal muscle weakness in OI mice.
Gremminger et al., 2019 and 2021, compromised exercise capacity, mitochondrial dysfunction, and altered muscle-bone signaling in OI models.
Ireland et al., 2025, updated review of muscle impairments.
7. Ocular System
Blue sclerae result from altered light reflectance in the presence of abnormal scleral collagen. In other-words we see the traditionally WHITE part of the eye as BLUE, because the lower collagen volume/quality makes the sclera thinner. Corneal defects also occur because collagen is the dominant corneal protein. PubMed Central
Research in the 1990's soidified the folowing:
genuine structural thinning of the sclera,
NOT just a cosmetic side effect
The sclera itsef I actually thinner
limiting or eliminating some visua corrective surgical options
tonometry may give falsely low readings in eyes with thinner corneas
Representative papers:
Treurniet et al., 2022, systematic review of ocular characteristics and complications.
Lyster et al., 2022, risk of eye diseases in OI.
Chou et al., 2023, altered corneal biomechanics in OI.
Mangiantini et al., 2024, corneal alterations in a larger clinical sample.
8. Skin and Connective Tissue
Your skin is the largest single organ in your body, regardess, treat it kindly:
Representative paper:
Gooijer et al., 2019, bleeding and bruising in OI.
Grol et al., 2021, tendon and motor phenotypes in the Crtap-/- mouse model.
Chretien et al., 2022, biomechanical and microstructural abnormalities of tendon-to-bone unit in oim mice.
Sinkam et al., 2023, reduced tendon mechanical properties in Col1a1Jrt/+ mice.
9. Cellular Mechanisms
Perhaps the most intellectually transformative body of research since 1996 has been at the cellular level — tracing how defective collagen production leads to a system-wide pathological cascade. The interplay between intracellular stress, oxidative damage, and inflammation not only underlies cellular dysfunction but also the multisystemic manifestations of OI. MDPI
10. Chronic Pain
A dedicated topical meeting on pain and OI — sponsored by the OI Federation of Europe — produced a landmark summary document that captured the scope of pain as an independent and under-treated dimension of the disease. (TheOIGuy wil post a copy of that publication as soon as we can gain access)..
It persists despite pharmacological and non-pharmacological interventions
, interferes with daily activities,
correlates with fatigue, I
s independent of the severity of the condition,
constitutes a disability factor,
and is often, but not always located in the back.
OI pain is not simply explained by fractures or deformity. Neuropathic, inflammatory, and mechanical components all appear to play roles.
Representative papers:
Dahan-Oliel et al., 2016, mixed-methods quality-of-life review.
Nghiem et al., 2018, pain experiences of adults with OI.
Cortés et al., 2022, chronic pain in adults with OI.
Mc Donald et al., 2023, systematic review of HR-QOL in adults with OI.
11. Expanded Genetic Landscape — 22+ OI Types
The genetic research itself since 1996 has been transformative. The discovery of recessive forms beginning in the mid-2000s proved that OI is not solely a collagen-quantity or collagen-structure problem
OI is now understood as a collagen-related disorder:
caused by defects of genes whose protein products interact with collagen for folding,
post-translational modification,
processing and
trafficking,
affecting bone mineralisation and
osteoblast differentiation
This section specifically mentions 22 classifications of types, and doesnt even mention subtypes (Type1 for example has 2 widely accepted sub types), but this changes depending uping WHO you are receiving your informtion from, when THEY received the information, and what they feel is important. A wise man once said,” A Hammer see's every problem as a NAIL.” I think applies to us as well.
Conclusion
The picture that has emerged from nearly three decades of post-1996 research is of a disease where the bone fractures are, in a sense, only the most visible symptom of a far more pervasive collagen deficit.
Defective type I collagen — which constitutes roughly 80% of the collagen in lung and cardiac tissue, dominates the cornea, forms the structural scaffolding of the inner ear, and provides integrity to blood vessel walls — leaves no organ system entirely untouched.
OI requires multidisciplinary care, including:
