A 43-yr-old female visited a nearby hospital because of abnormal shadows including multiple nodules and reticular shadows on chest radiography found at an annual medical checkup in 2005. A bronchoscopic examination was performed. They were unable to obtain a biopsy specimen from one of the nodules in S10 of the left lung because the patient had a strong bleeding tendency. She was referred to this hospital for further examination on June 30, 2005.
On admission, her height was 157.5 cm and weight, 50.3 kg. Her consciousness was clear. The conjunctivas were anemic and not jaundiced. Her heart sounds were normal. Fine crackles were audible in the right lower lung field. The abdomen was not distended. Her inguinal lymph nodes were palpable and no other superficial lymph nodes were palpable. She was experiencing slight polyarthralgia, however, radiography films showed no joint anomalies.
The laboratory data were: erythrocyte sedimentation rate, 119 mm/1 hr; white cell count, 8,900/µL; hemoglobin, 8.4 g/dL; platelet count, 39.4×104/µL; serum aspartate aminotransferase, 22 IU/L; alanine aminotransferase, 22; total protein, 9.7 g/dL; albumin 2.6; creatinine, 0.48; PT, 13.1 sec (INR 1.45); aPTT, 39.6 (control, 10.4); fibrinogen, 750 mg/dL; KL-6, 277 U/mL (reference range <500); C-reactive protein, 11.7 mg/dL (<0.3); serum immunoglobulin (Ig)G, 4,570 (870-1740); IgA, 491(110-400), IgM, 706 (35-220), CH50, 52.3 U/mL (30-50), soluble IL-2 receptor, 1,400; serum IL-6, 6.8 pg/mL (<4); rheumatoid factor (RF), 1,330 IU/mL (<20). Autoantibodies, including antinuclear antibody, anti-ds-DNA, anti-Sm, anti-RNP, cytoplasmic antineutrophil cytoplasmic antibody (ANCA), and myeloperoxidase-ANCA were all negative. M-protein was not noted in serum immunoelectrophoresis. Bone marrow aspiration showed hyperplasia with no abnormal morphology on smear specimens.
Chest radiographys showed multiple nodules and reticular shadows mainly in the lower lung field. Chest CT scan disclosed a slight enlargement of the mediastinal lymph nodes, centrilobular nodules, thin-walled cysts, the thickening of the bronchovascular bundles, and ground-grass opacities, all of these findings were compatible with those of lymphocytic interstitial pneumonia (LIP; ) (, ). 67Gallium citrate scintigraphy did not reveal any evident accumulation.
A lung surgeon and a thoracic physician declined to perform a lung biopsy because of her bleeding tendency (bleeding time: 6 min 30 sec) and poor general condition. A biopsy of an inguinal lymph node was obtained for making a definite diagnosis (). She was diagnosed with MCD and undifferentiated arthritis based on the characteristic pathology of the specimen of the inguinal lymph node, CT findings of the bilateral lung lesions and laboratory data.
She was initially administered intravenous corticosteroid (methylprednisolone, 500 mg/day, 3 consecutive days) followed by oral corticosteroid (methylprednisolone, 16 mg/day), and, 375 mg/m2 rituximab every week for 4 weeks. The polyarthralgia instantly disappeared; however, none of the other clinical and laboratory parameters were fully resolved. Therefore the therapeutic regimen was changed to tocilizumab (8 mg/kg, every 2 weeks), oral corticosteroid (methylprednisolone, 16 mg/day) on October 25, 2005. The patient requested that the interval between tocilizumab to be increased to more than every two weeks. The dose of corticosteroid in combination with tocilizumab should be kept as low as possible to avoid various side effects, such as osteoporosis, hyperglycemia, and hypertension. It is indicated for the treatment of rheumatoid arthritis in Japan. The addition of tacrolimus to the regimen was considered to fulfill such requirements. Both the possible merits and demerits of the drug were explained to the patient and her oral consent was obtained. Tacrolimus (3 mg/day) was introduced on November 10, 2005. Laboratory findings, including anemia, hypergammaglobulinemia, and an increase in acute phase proteins responded to this regimen (). The enlargement of mediastinal lymph nodes and abnormal shadows were also partially alleviated (). The intervals of the tocilizumab-administration sessions were extended from every 2 weeks to every 3 weeks from January 2006. Oral corticosteroid was gradually tapered from 16 mg/day finally to 4 mg/day. The dose of tacrolimus has been unchanged. The disease activity has been totally suppressed for 36 months by this maintenance regimen.
The formula for computing Cockcroft-Gault is given by CrCl = ((140 - age) * adjusted weight * (gender_coefficient)) / (serum creatinine * 72), where the gender_coefficient is 1 if male, and 0.85 if female. The serum creatinine concentration is in mg/dL.
The patient's gender is female, which means that the gender coefficient is 0.85.
The patient is 43 years old. 
The concentration of creatinine is 0.48 mg/dL. 
The formula for computing the patient's BMI is (weight)/(height * height), where weight is the patient's weight in kg and height is the patient's height in m.
The patient's height is 157.5 cm, which is 157.5 cm * 1 m / 100 cm = 1.575 m. The patient's weight is 50.3 kg. The patient's bmi is therefore 50.3 kg / (1.575 m * 1.575 m) = 20.277 kg/m^2.The patient's BMI is 20.3, indicating they are normal weight.
Because the patient is normal, we take take minimum of the ideal body weight and the patient's body as the patient's adjusted weight for the Cockroft-Gault Equation. Hence, the adjusted body weight is the minimum of the two giving us an adjusted body weight of 50.118 kg.

Using the Cockcroft-Gault equation:
CrCl = ((140 - age) * adjusted weight * gender_coefficient) / (serum creatinine * 72).
Plugging the patient's values gives us ((140 - 43) * 50.118 * 0.85) / (0.48 * 72) = 119.567 mL/min. Hence, the patient's creatinine clearance is 119.567 mL/min.