Differential Diagnosis

The patient's symptoms of headache, diarrhea, dyspnea on exertion, nonproductive cough, hoarseness, subconjunctival and retinal hemorrhages, and a generalized macular rash suggest a complex and potentially severe underlying condition. The following differential diagnoses are considered:

• Single most likely diagnosis
  • Vasculitis (e.g., Granulomatosis with Polyangiitis): The combination of respiratory symptoms (dyspnea, cough, hoarseness), eye findings (subconjunctival and retinal hemorrhages), and a generalized macular rash, along with systemic symptoms like headache and diarrhea, points towards a vasculitic process. Vasculitis can affect multiple organ systems and present with a wide range of symptoms.
• Other Likely diagnoses
  • Infectious diseases (e.g., Endocarditis, Meningitis): The presence of fever (not explicitly mentioned but possible given the context), headache, and systemic symptoms could suggest an infectious process. Endocarditis, for example, can cause embolic phenomena leading to retinal and subconjunctival hemorrhages, and meningitis could explain the headache and potentially the rash if it's a specific type like meningococcemia.
  • Connective Tissue Diseases (e.g., Systemic Lupus Erythematosus): These diseases can present with a wide array of symptoms including rash, joint effusions, and systemic symptoms. However, the specific combination of symptoms, especially the respiratory and eye findings, makes this less likely than vasculitis.
• Do Not Miss (ddxs that may not be likely, but would be deadly if missed.)
  • Meningococcemia: Although less likely given the full spectrum of symptoms, meningococcemia can present with a rash, fever, and systemic symptoms. It's a medical emergency due to its high mortality rate if not promptly treated.
  • Thrombotic Thrombocytopenic Purpura (TTP): This condition can cause a variety of symptoms including neurological findings, renal dysfunction, fever, and thrombocytopenia. The presence of a rash and systemic symptoms could potentially fit, although TTP is more typically associated with microangiopathic hemolytic anemia and thrombocytopenia.
• Rare diagnoses
  • Ehlers-Danlos Syndrome with associated vascular complications: This genetic disorder can lead to fragile blood vessels and potentially explain some of the hemorrhagic findings. However, it's a rare condition and would not typically present with the full spectrum of symptoms described.
  • Scurvy: Caused by vitamin C deficiency, scurvy can lead to a variety of symptoms including joint pain, rash, and potentially some hemorrhagic manifestations due to blood vessel fragility. It's an unlikely diagnosis given the modern diet and availability of vitamin C but could be considered in cases of severe nutritional deficiency.

Expected Findings on Physical Exam

Given the differential diagnoses, expected findings on physical exam could include:

• Joint effusions: More likely in connective tissue diseases or vasculitis.
• Periorbital edema: Could be seen in nephrotic syndrome, heart failure, or as part of a systemic disease like vasculitis or connective tissue disease.
• Altered mental status: Might be present in severe infections (like meningitis), vasculitis affecting the CNS, or in conditions leading to metabolic derangements.
• Hyperreflexia: Could be seen in conditions affecting the central nervous system, such as vasculitis or infections.