gistfile1.cs

var document = XElement.Load("file.xml");

return 
    document.Descendants("patient")
            .Where(e => e.Attribute("id").Value == "1")
            .Select(e => new PatientRecord
            {
                FirstName = e.Attribute("firstName").Value
                ,
                LastName = e.Attribute("lastName").Value
                ,
                ExamFindings = e.Descendants("exam")
                                .OrderByDescending(child => (DateTime)child.Attribute("date"))
                                .Select(child => new Exam
                                    {
                                        Date = DateTime.Parse(child.Attribute("date").Value)
                                        ,
                                        Findings = child.Value
                                    })
            })
            .Single();