Rheumatological disorders rarely present to emergency. Systemic JIA and systemic lupus erythematosus (SLE) are two rheumatological disorders which can present acutely and can have a stormy course. A considerable proportion of this risk is due to the development of macrophage activation syndrome. Macrophage activation syndrome (MAS) is a syndrome of organ dysfunction due to cytokine storm induced by uncontrolled inflammation. It is characterized by hematological abnormalities (pancytopenia), hepatitis, central nervous system (CNS) dysfunction (seizures, altered sensorium), and coagulopathy [5, 6]. S presented with a subacute course with thrombocytopenia, icterus, and CNS dysfunction. However, her icterus was due to direct hyperbilirubinemia, whereas the liver dysfunction in MAS is typically associated with transaminitis without significant hyperbilirubinemia [7]. In addition the lung parenchyma is rarely involved in sJIA. Thus a possibility of disseminated sepsis which had probably been partially treated was considered and she was investigated further (Fig. 23.2).

In view of the abnormal chest X–ray, she underwent a CT scan which demonstrated bilateral pleural effusion right greater than left with bilateral consolidation. Multiple areas of breakdown with abscess formation were observed (Fig. 23.3). The MRI of the pelvis showed right–sided psoas abscess with right hip synovitis and altered signal in the right femur (Fig. 23.4). Blood culture, which had been sent at admission, grew methicillin–resistant staph aureus (MRSA). She was treated with prolonged IV antibiotics and underwent surgery to drain the collections. She recovered slowly. Post–recovery workup for possible immunodeficiency was negative.

Septic arthritis in children is much more common in boys, with the hip and knee joints commonly involved. It is generally a disease of children less than 2 years of age. In the large majority, the arthritis is monoarticular [8]. However as seen in the above patient’s condition, exceptions should be kept in mind. Hence, septic arthritis should always be considered in a sick child even if they present with polyarticular arthritis. When in doubt a synovial fluid aspiration and analysis will usually provide the answer. We also expect patients with septic arthritis to have high-grade fever and to have leukocytosis [9]. However case series have shown that one-third to one-half of the patients with septic arthritis are afebrile or have low-grade fever at presentation [8, 10]. S also had no fever at the outset and developed high-grade fever a week into her illness.

Her culture grew MRSA which was long regarded as a nosocomial infection. However community-acquired MRSA infections have increasingly been reported. The majority of patients are children with bone and joint infections and account for 2.8–43 % of the patients [9].

It is important to consider septic arthritis and treat early in order to avoid irreversible damage to the cartilage and joint. The mortality with septic arthritis is quite low in recent series [9]. Early recognition and differentiation of these mimics is important so that patients would receive appropriate therapy.

Under 0.25–1 % of patients presenting with musculoskeletal manifestations to pediatric or pediatric rheumatology units are diagnosed as having a malignancy [11, 12]. The most common malignancy diagnosed in such situations is an acute lymphoblastic leukemia (ALL). Other malignancies are acute myeloid leukemia, lymphoma, neuroblastoma, and Ewing’s sarcoma [11–13]. Between 18 and nearly 40 % of patients with ALL present with musculoskeletal manifestations. In fact, as seen in PK’s case, ALL patients with musculoskeletal manifestations are more likely than other ALL patients to have normal hematological indices on peripheral blood examination [14]. Thus it becomes imperative to maintain a high degree of suspicion and perform a bone marrow examination even in the presence of a normal peripheral blood smear. The long-term prognosis is as good if not better in the subset of ALL patients who present with musculoskeletal complaints compared to those who do not [14–16]. The use of steroids in patients with ALL causes a temporary improvement in clinical symptoms, and thus the clinician may be lulled into thinking that the patient has responded to the therapy. Steroids can cause difficulty in interpretation of the bone marrow. Treatment with just steroids or even subtherapeutic doses of methotrexate may worsen the prognosis in ALL patients by allowing the malignant cells to develop resistance. Thus by treating with steroids and delaying diagnosis, we would unnecessarily be exposing these children (ALL patients with musculoskeletal complaints) who have a good prognostic outlook, to a more severe course of disease. Some characteristics which help differentiate patients with malignancies from JIA patients are described elsewhere in the book as well as in the referenced publications [16–18].

The detection of synovitis or inflammation in a child with a painful joint has been hampered by the lack of standardized examination. The same has been sought to be addressed by the creation of a standardized mode of examination of the pediatric musculoskeletal system. The screening examination known as pGALS was validated and has slowly become part of standard pediatric medical curriculum [19]. Any child with an abnormal pGALS examination needs to undergo a more rigorous and detailed examination of individual joints which is standardized in the pREMS examination system [20].

A pGALS examination in patient L did not demonstrate any abnormality. However in view of strong clinical suspicion based on history, a pREMS and a musculoskeletal ultrasound were performed. Ultrasonography has been found to be quite useful for the detection of subclinical synovitis in adult patients with inflammatory arthritis [21]. Its use has been validated by its inclusion into the ACR/EULAR 2010 classification criteria for rheumatoid arthritis [22]. Compared to its use in adults, the use of musculoskeletal ultrasound in children has lagged behind. Studies have shown that it is a useful technique to detect subclinical synovitis as well as to determine the exact pathology in swollen joints (synovitis vs. tenosynovitis). This is particularly important in pediatrics where JIA patients are classified according to the number of joints involved [23].

She had remained well in the intervening period apart from another episode of pain in an ankle joint a few months ago. Just like the first episode, this episode too had lasted for a few days and improved spontaneously. She also had an episode of culture–proven enteric fever. At second presentation she had moderate–grade fever for 2 weeks with pain and swelling in several joints for a week. She had been investigated for recurrence of enteric fever and workup had not yielded a result. Clinical examination revealed inflammatory arthritis of almost all the metacarpophalangeal joints , the proximal interphalangeal joints, both wrists, as well as both ankles and the small joints of the feet. Her left knee was swollen and tender. She was investigated and found to have high ESR (62 mm/h) with a normal CRP (1.7 mg/L). Her hemogram, liver function test, and renal function test including urine routine were normal. Further evaluation demonstrated a positive ANA by IFA at 1:100 titer nucleoplasm granular pattern 2+ fluorescence intensity, RF was positive (33.7 IU/ml), eye evaluation showed significant dry eye with loss of tear film integrity, and Schirmer’s test was 3 mm on the right and 4 mm on the left. In view of significant dry eye detected on ophthalmological examination, she was evaluated further and found to have a negative anti–CCP (0.5U/ml), and ANA profile was positive for anti-Ro–52 antibodies. Coomb’s test, angiotensin–converting enzyme, and complements were normal. Minor salivary gland biopsy showed septal infiltrate of lymphocytes and plasma cells. Periductal nodular aggregates were seen resulting in a Grade 4 classification by Chisholm and Mason criteria. Focal minimal fibrosis was noted.