Interactive Quiz: Joint Pain

Welcome to Rheumatology Consultant's latest interactive diagnostic quiz. Over the next few pages, we'll present a case and ask you to make the diagnosis and treat the patient. Along the way, we'll provide details about the case, and at the end, we'll share the patient's outcome. Ready to get started? >> , First, let’s meet the patient… A 4-month-old girl presented with signs of joint pain and hyperpigmentation of the skin over the joints. She had been born at 33 weeks of gestation via cesarean delivery due to fetal distress to a mother with a history of systemic lupus erythematosus (SLE). The pregnancy had been complicated by a maternal SLE flare requiring hydroxychloroquine treatment during the second and third trimester and by placental insufficiency leading to intrauterine growth restriction (IUGR). The girl had remained in the neonatal intensive care unit (NICU) for 5 weeks with a relatively uncomplicated course, primarily working on feeding and growing. One week prior to discharge from the NICU, at 4 weeks of age, she was noted to have reduced movement at the shoulders, and raising her arms appeared to cause her pain.  Based on the presentation, what might be your initial diagnosis?Septic arthritis of the shoulderErb palsyParsonage-Turner Syndrome Are you correct? >> , Answer: Erb palsy   She received a clinical diagnosis of Erb palsy and was discharged home with outpatient physical therapy. After returning home, her signs of joint pain progressively worsened. She was unable to lift her arms at the shoulders and cried out with movement. At approximately 6 weeks of age, her parents noticed discoloration on the infant’s knuckles and ankles. She was admitted at an outside hospital for 5 days. She had normal levels of electrolytes, including phosphorus and calcium, as well as normal rheumatologic laboratory test results. Echocardiography findings were unremarkable. What other diagnostic scan would you perform?Magnetic resonance imagingRadiologic skeletal surveyNone Are you correct? >> , Answer: Radiologic skeletal survey A radiologic skeletal survey showed periosteal reactions in both femurs and diffuse osteopenia but no fractures. She was discharged home without a diagnosis. After discharge, her joint pain and skin discoloration continued to worsen. The joint pain and stiffness began to involve her elbows and knees, and the skin discoloration spread to her wrists and elbows. Her only other illness was an uncomplicated upper respiratory tract infection. She had never traveled outside of the state, and her parents denied any trauma. On examination, the patient was small for her age but was well-appearing. She had reduced movement of her extremities and cried with any manipulation of the shoulders, elbows, wrists, knees, and ankles. No obvious joint swelling or erythema were present. It was difficult to fully extend at the shoulder, elbow, and knee, although slow passive range of motion was possible. Symmetric, brownish purple hyperpigmentation was present bilaterally over the metacarpophalangeal (MCP) joints, the lateral aspect of the wrists, the medial aspect of the elbows, the medial and lateral malleoli, and the proximal interphalangeal joints of the feet (Figures 1 and 2). A skeletal survey was performed, the results of which showed generalized slightly decreased bone density but no acute or healing fractures. Abdominal ultrasonography findings were normal.  She continued to appear to have significant pain with any manipulation of her extremities, which improved with the administration of morphine and ibuprofen. What might your next step be?Send the patient home with no diagnosisConsult a genetics specialistConsult an infectious disease specialist Are you correct? >> , Answer: Consult a genetics specialist Genetics, as well as dermatology, specialists were consulted, with further testing confirming the diagnosis of infantile systemic hyalinosis (ISH). Genetic test results were positive for a homozygous mutation of the anthrax toxin receptor gene (ANTXR2), confirming the diagnosis of ISH. A dermatologist performed a punch biopsy of a hyperpigmented lesion on the infant’s left foot, the results of which demonstrated sclerosis of the deep dermis with elevation of the eccrine coils, with apparent loss of the peri-eccrine fat, and with relative loss of the CD34+dermal dendritic cells at the base of the specimen. Which of the following would least likely be included in your management plan for this patient?Surgical excision of skin lesionsOral morphine for painPhysical therapy Are you correct? >> , Answer: Surgical excision of skin lesions  The patient was discharged home with oral morphine as needed for pain, physical therapy, and outpatient follow-up with medical genetics, palliative care, and dermatology specialists. In some cases, surgical excision of skin lesions can be considered, although recurrence can occur, and partial or radical gingivectomy may be helpful for gingival hyperplasia. ISH is a progressive disease that typically results in death by aged 2 years, most often secondary to intractable diarrhea, recurrent infections, and organ failure. Cases of longer survival have been reported. To read the full case report, see: Goldstein J, Meepos L, Zipkin R. Infantile systemic hyalinosis. Consultant. 2019;59(3):90-92. https://www.consultant360.com/article/rheumatology/infantile-systemic-hyalinosis?page=0.