Sandbox: differentialdx maria

Type of osteochondroma	Features
Solitary osteochondroma	Non-hereditary 85% of osteochondromas No genetic mutations Located in long bones, 85% of osteochondromas Onset is in early adolescence
Multiple osteochondromas (hereditary)	Hereditary Approximately 20% of osteochondromas Related genetic mutations EXT-1 and EXT-2, Early onset of disease (newborn or children)

Genes implicated in HNPCC	Frequency of mutations in HNPCC families	Locus
MSH2	approximately 60%	2p22
MLH1	approximately 30%	3p21
MSH6	7-10%	2p16
PMS2	relatively infrequent	7p22
PMS1	case report	2q31-q33
TGFBR2	case report	3p22
MLH3	disputed	14q24.3

Type of osteoid osteoma	Characteristics
Intracortical	Dense sclerosis around the nidus
Periosteal	Periosteal reaction
Cancellous (medullary)	Produces very little reactive bone
Subarticular	Simulates arthritis as it produces synovial reactions

Differential Diagnosis	Similar Features	Differentiating Features
Osteoblastoma	Benign, male predilection, and also present in long bones	In osteoblastoma, differentiating features include: uncommon tumor, affect the axial skeleton more frequently and lesions are typically larger than 2 cm
Brodie abscess	Present in children, limb pain, and ocassionaly affects long bones	In brodie abscess differentiating features include: fever, subacute onset, and location is usually affects the metaphysis of tubular bones
Osteosarcoma	Affects same group of population (children and adolescents), patients usually present with bone pain, and the location is usually long bones	In osteosarcoma, differentiating features include: malignancy, infiltration to surrounding tissue, and elevation of serum alkaline phosphatase (ALP)
Enostosis	Affects same group of population (children and adolescents), small size, and the location is usually long bones	In enostosis, differentiating features,include: pathognomonic radiological appearance, incidental finding

Differential Diagnosis	Similar Features	Differentiating Features
Fibrous dysplasia	Benign, often an incidental finding, and affects the same group of patients.	In fibrous dysplasia, differentiating features include: More common presentation is on ribs: 28%, no gender predilection, and complete resection is usually not possible.
Osteoblastoma	Benign, incidental, and male predilection.	In osteoblastoma, differentiating features include: normally affect the axial skeleton, lesions are typically larger than 2 cm, and surgical excision is often the treatment of choice.
Adamantinomas	Benign, slow growing, similar clinical onset.	In adamantinomas , differentiating features include: locally aggressive tumor, common in the 3rd to 5th decades of life, location is usually confined to the jaw.
Chronic sinusitis	Affects same group of population (young to middle aged adults), clinical onset is similar.	In chronic sinusitis, differentiating features include: fever, previous history of acute sinusitis, and lack of facial deformation or imaging findings compatible with osteoma.

Differential Diagnosis	Similar Features	Differentiating Features
Cardiac tamponade	Elevated jugular venous pressure, reduced diastolic filling of the right ventricle, and hypotension.	In cardiac tamponade, differentiating features include: muffled heart sounds, pericardial rub, and electrocardiographic changes.
Chronic obstructive pulmonary disease	Elevated jugular venous pulse (JVP), shortness of breath, and tachypnea.	In cardiac tamponade, differentiating features include: history of chronic bronchitis, coarse crackles with inspiration, and spirometry with FEV1/FVC < 70%.
Mediastinitis	Elevated venous pressure, tachypnea and shortness of breath.	In mediastinitis, differentiating features include: fever, positive confirmation of organisms and elevated leukocytes.
Pneumonia	Hypotension, tachypnea,cough, and chest pain.	In pneumonia, differentiating features include: Bronchial breath sounds, leukocytosis with left shift, positive blood culture and altered laboratory findings (procalitonin).
Acute respiratory distress syndrome	Low blood pressure,hypotension, and shortness of breath.	In cardiac acute respiratory distress syndrome, differentiating features include: acute onset, bilateral infiltrates on chest radiograph sparing costophrenic angles and pulmonary wedge pressure < 18 mmHg.
Syphilis	Enlarged lymph nodes, hypotension and dysphagia.	In syphilis, differentiating features include: Positive treponemal tests, history of unprotected sex, and superficial mucosal patches.

Differential Diagnosis	Similar Features	Differentiating Features
Familial adenomatous polyposis (FAP)	Familial inheritance, increased risk of colorectal cancer, extra-colonic tumors.	Autosomal recessive, 100+ polyps and age under 40, centinel tumors are differently located than HNPCC, such as: Osteomas, dental anomalies, congenital hypertrophy of the retinal pigment epithelium (CHRPE)
Juvenile polyposis	Familial inheritance, autosomal dominant, high risk of GI and non GI cancer, also a germline mutation.	Gastrointestinal hamartomatous polyps, on physical exam lip pigmentation is common.
Cowden syndrome	Rare autosomal dominant inherited disorder, increased risk of colorectal cancer, also has gene mutations.	Intestinal hamartomatous polyps, physical exam may show macrocephaly, gene affected PTEN.