A 16 year-old presents for evaluation of a rash. The patient notes that it started on their back, with multiple spots, and has spread to their upper chest and arms. It itches a little. The patient also reports sweating more than before because their new summer job involves being outdoors. On physical examination, you note hyperpigmented, oval macules scattered more prominently around the upper back, chest, neck, and upper arms, as well as under the arms. Based on this description, what is the most likely diagnosis?

Shoulder injuries following trauma are evaluated using specific physical examination maneuvers that help localize the affected anatomical structure. The crossover test (also known as the horizontal adduction or scarf test) is used to assess pathology of the acromioclavicular (AC) joint. Pain elicited when the arm is moved across the chest indicates stress or inflammation of this joint. Accurate interpretation of special tests helps differentiate AC joint injury from rotator cuff, biceps tendon, or glenohumeral pathology.

Rationale:
A. Rotator cuff injuries typically present with pain during abduction, especially between 60–120 degrees (painful arc), and weakness with shoulder movement. These injuries are associated with positive drop arm or empty can tests rather than pain specifically with horizontal adduction across the chest. The crossover test is not specific for rotator cuff pathology.

B. Bicipital tendon pathology presents with anterior shoulder pain and tenderness over the bicipital groove. Pain is typically reproduced with Speed’s or Yergason’s tests rather than the crossover maneuver. The localization of pain in this case does not match the anterior tendon involvement typical of biceps tendinitis.

C. Glenohumeral joint injury involves deep shoulder pain, reduced range of motion, and instability, often worsened by active and passive movement in multiple planes. It is not specifically reproduced by horizontal adduction across the chest. The crossover test is more targeted to the AC joint rather than the glenohumeral articulation.

D. Acromioclavicular joint is the most likely site of injury because the crossover test places stress directly on this joint by horizontally adducting the arm across the body. Pain reproduced with this maneuver indicates AC joint irritation or separation, commonly seen after falls onto the shoulder. This test is highly specific for AC joint pathology, making it the correct answer.

Assessment of unexplained physical and behavioral changes in older adults requires careful consideration of both medical and psychosocial causes. Elder abuse should be suspected when there are signs of injury, behavioral withdrawal, and caregiver dominance during interactions. Bruising, reduced eye contact, and altered patient participation in conversation can indicate possible neglect, physical abuse, or coercion. Identifying abuse early is essential to ensure patient safety and initiate protective interventions.

Rationale:
A. Elder abuse is the most concerning diagnosis because it involves physical, emotional, or psychological harm inflicted on an older adult, often by a caregiver. Unexplained bruises and scars raise concern for physical abuse, while reduced eye contact and decreased engagement may indicate fear, intimidation, or emotional withdrawal. The daughter controlling the interaction and the patient’s deviation from baseline behavior strongly support possible abuse or neglect.

B. Anemia may cause symptoms such as fatigue, pallor, and weakness but does not explain bruising patterns combined with behavioral changes in caregiver interaction. While some bleeding disorders can contribute to bruising, anemia alone does not account for the observed psychosocial dynamics or decreased patient engagement. Therefore, it does not fully explain the clinical picture.

C. Depression in older adults can present with withdrawal, reduced eye contact, and decreased communication. However, depression does not typically cause multiple unexplained bruises and scars. The combination of physical injury and caregiver dominance makes abuse a more concerning and comprehensive explanation than depression alone.

D. Mild cognitive impairment involves subtle memory and cognitive changes but does not usually result in behavioral withdrawal due to caregiver control or unexplained physical injuries. Patients with cognitive decline may still engage in conversation, and bruising would not be explained by this condition. The presence of physical trauma and altered interaction patterns suggests a different underlying cause.