Differential Diagnosis for Marfanoid Features

Given the patient's presentation with marfanoid features, a negative genetic screen for Marfan syndrome, a normal echocardiogram, and a normal ophthalmologic exam, the differential diagnosis can be categorized as follows:

• Single Most Likely Diagnosis

  • Homocystinuria: This condition is known for causing marfanoid habitus (tall stature, long limbs, and joint hypermobility) similar to Marfan syndrome but is due to an error in amino acid metabolism. The negative genetic screen for Marfan syndrome and the absence of significant cardiac or ocular findings make homocystinuria a plausible diagnosis, as it can present with similar skeletal features but typically involves other systemic issues such as thromboembolic events and developmental delays.

• Other Likely Diagnoses

  • Ehlers-Danlos Syndrome (EDS): While EDS can present with joint hypermobility and skin features, some types may also exhibit a marfanoid habitus. The lack of specific genetic findings for Marfan syndrome and the presence of marfanoid features without the typical cardiovascular or ophthalmologic complications could suggest certain types of EDS.
  • Loeys-Dietz Syndrome: This syndrome shares some features with Marfan syndrome, including aortic aneurysm risk, but also often presents with craniofacial abnormalities and skin features. However, the normal echocardiogram might make this less likely unless the syndrome is in an early stage or a variant form.
  • Congenital Contractural Arachnodactyly (Beals Syndrome): This condition presents with marfanoid habitus, contractures, and ear abnormalities. The absence of significant cardiac or ocular findings could align with this diagnosis, although specific genetic testing would be needed for confirmation.

• Do Not Miss Diagnoses

  • Familial Thoracic Aortic Aneurysm and Dissection (FTAAD): Although the echocardiogram is normal, FTAAD could be considered due to the risk of aortic aneurysm and dissection, which might not always be evident on initial screening. Regular follow-up and possibly more detailed aortic imaging might be warranted.
  • Turner Syndrome: While typically diagnosed in females with short stature, some cases might present with marfanoid features. The absence of other typical Turner syndrome features and the negative genetic screen might make this less likely, but it's crucial not to miss due to its implications for growth, development, and reproductive health.

• Rare Diagnoses

  • Shprintzen-Goldberg Syndrome: A rare condition characterized by marfanoid habitus, craniosynostosis, and developmental delays. The diagnosis would require specific genetic testing and consideration of other systemic features.
  • Multiple Endocrine Neoplasia Type 2B (MEN2B): Presents with a marfanoid body habitus, mucosal neuromas, and a high risk of medullary thyroid carcinoma. The absence of other specific features might make this less likely, but it's a critical diagnosis due to its implications for cancer risk and management.