| Phenotype | Phenotype type | Typical onset | Progression / severity | Frequency / quantitative data | Suggested HPO term(s) | Evidence |
|---|---|---|---|---|---|---|
| Coarse/dysmorphic facial features | Physical manifestation | Prenatal-neonatal or first months of life | Early, prominent, severe in classic MLII | Presenting feature in 47.4% of MLII cases in systematic review | Coarse facial features (HP:0000280); Dysmorphism | (pqac-00000013, pqac-00000001) |
| Developmental delay / global developmental impairment | Neurodevelopmental sign | Infancy | Progressive impairment in function, but longitudinal data suggest continued slow skill gain rather than true neurocognitive regression | Presenting feature in 24.2%; mean developmental quotient 36.7% (SD 20.4) at last assessment; gain of 0.28 age-equivalent score points/month (95% CI 0.17-0.38) | Global developmental delay (HP:0001263); Intellectual disability (HP:0001249) | (pqac-00000013, pqac-00000021) |
| Skeletal abnormalities / dysostosis multiplex | Physical manifestation / radiographic abnormality | Prenatal-infancy | Progressive, severe multisystem skeletal disease | Presenting feature in 20.0%; severe orthopaedic disease and dysostosis multiplex reported in all patients in CNS cohort | Dysostosis multiplex; Abnormality of the skeletal system (HP:0000924) | (pqac-00000013, pqac-00000019, pqac-00000001) |
| Growth retardation / short stature | Physical manifestation | Infancy | Progressive growth failure | Presenting feature in 12.6%; severe growth abnormalities described | Growth delay (HP:0001510); Short stature (HP:0004322) | (pqac-00000013, pqac-00000001, pqac-00000000) |
| Restricted joint range of motion / joint stiffness | Clinical sign | Infancy to early childhood | Progressive; common musculoskeletal hallmark | Presenting feature in 10.7%; main manifestation in recent Chinese cohort | Joint stiffness (HP:0001387); Decreased range of motion of joint | (pqac-00000013, pqac-00000000) |
| Abnormal skull shape / craniosynostosis-related skull changes | Physical manifestation | Infancy | May progress; part of dysostosis multiplex spectrum | Presenting feature in 10.7% | Abnormal skull morphology (HP:0000928); Craniosynostosis (HP:0001363) | (pqac-00000013, pqac-00000005) |
| Cardiac involvement | Organ/system involvement | Prenatal-neonatal or infancy | Serious contributor to mortality | Frequently described clinically; cardiac failure accounted for 15/93 reported deaths and combined cardiopulmonary causes were common | Abnormality of the cardiovascular system (HP:0001626); Heart failure (HP:0001635) | (pqac-00000013, pqac-00000001) |
| Respiratory involvement / recurrent infections / respiratory failure | Organ/system involvement | Prenatal-neonatal or infancy | Progressive; major life-limiting complication | Respiratory failure 24/93 and pneumonia 32/93 among reported causes of death | Recurrent respiratory infections (HP:0002205); Respiratory insufficiency (HP:0002093) | (pqac-00000013, pqac-00000001, pqac-00000005) |
| Hip dysplasia | Musculoskeletal sign | Childhood (often evident early) | Progressive orthopedic burden | 9/11 patients (81%) in CNS cohort | Hip dysplasia (HP:0001385) | (pqac-00000019) |
| Sensorineural hearing impairment | Sensory abnormality | Childhood | Variable, often chronic | Confirmed in 6/11 patients (55%) | Sensorineural hearing impairment (HP:0000407) | (pqac-00000019) |
| Middle ear disease | ENT manifestation | Childhood | Recurrent/chronic | Present in 10/11 patients (91%) | Otitis media; Middle ear abnormality | (pqac-00000019) |
| Ophthalmologic abnormalities | Sensory/ocular manifestation | Childhood | Variable | Reported in 7/11 patients (63%) | Abnormality of the eye (HP:0000478) | (pqac-00000019) |
| Carpal tunnel syndrome | Neuromuscular / orthopedic sign | Childhood to later course | Can require intervention | 2/11 patients (18%) in CNS cohort | Carpal tunnel syndrome (HP:0100543) | (pqac-00000019) |
| Cervical spinal canal stenosis | Neuroimaging / structural abnormality | Childhood | Important complication; may require surveillance/intervention | 63% on neuroimaging | Cervical spinal canal stenosis; Spinal canal stenosis (HP:0003369) | (pqac-00000021, pqac-00000022) |
| Mild brain atrophy | Neuroimaging abnormality | Childhood | Reported as mild and non-progressive in cohort | 50% in figure/table summary from imaging context | Cerebral atrophy (HP:0002059) | (pqac-00000022) |
| White matter lesions / abnormalities | Neuroimaging abnormality | Childhood | Non-progressive / nonspecific in available cohort | Reported, frequency not numerically extracted in text summary | Abnormality of cerebral white matter (HP:0002500) | (pqac-00000021, pqac-00000022) |
| Hypotonia / reduced muscle tone | Neurologic sign | Infancy | Contributes to delayed motor development | Described in case-based clinical reports and HSCT follow-up | Hypotonia (HP:0001252) | (pqac-00000001) |
| Gingival hyperplasia | Craniofacial/oral sign | Infancy | Characteristic, progressive | Frequently cited as characteristic feature of MLII | Gingival overgrowth (HP:0000212) | (pqac-00000002, pqac-00000005) |


*Table: This table summarizes the major clinical and imaging phenotypes reported for mucolipidosis type II, including onset, progression, and approximate frequencies where available. It is useful for populating phenotype fields in a disease knowledge base and mapping features to HPO terms.*