Test your medicine knowledge with the MKSAP challenge, in partnership with the American College of Physicians.

A 62-year-old man is evaluated for a two-year history of enlargement and discomfort of the metacarpophalangeal joints of both hands. He works as a bank manager and leads a sedentary lifestyle. He does not have morning stiffness. He was diagnosed with type 2 diabetes mellitus three months ago for which he takes metformin.

On physical examination, vital signs are normal. Examination of the skin reveals generalized hyperpigmentation. There is bony enlargement of the metacarpophalangeal joints bilaterally but no evidence of synovial proliferation. Range of motion of the hands is full, and he can make a strong fist. Examination of the proximal and distal interphalangeal joints, knees, and hips is normal.

Laboratory studies:

Hemoglobin A1c	7.3%
Erythrocyte sedimentation rate	13 mm/h
Glucose (fasting)	100 mg/dL (5.6 mmol/L)
Rheumatoid factor	Negative
Anti–cyclic citrullinated peptide antibodies	Negative

Hand radiographs show joint-space narrowing and hook-shaped osteophyte formation in the metacarpophalangeal joints. Radiographs of the hips and knees are normal. These imaging studies reveal no evidence of chondrocalcinosis.

Which of the following is the most likely diagnosis?

A) Calcium pyrophosphate deposition disease
B) Diabetic cheiroarthropathy (stiff hand syndrome)
C) Hemochromatosis
D) Primary osteoarthritis
E) Rheumatoid arthritis

MKSAP Answer and Critique

The correct answer is C) Hemochromatosis. This item is available to MKSAP 15 subscribers as item 32 in the Rheumatology section. MKSAP 16 will release Part A on July 31. More information is available online.

This patient most likely has secondary osteoarthritis associated with hemochromatosis. Approximately 40% to 60% of patients with hemochromatosis develop an arthropathy with a presentation similar to that of osteoarthritis. The presence of symmetric pain and bony enlargement of the joints accompanied by radiographic findings of joint-space narrowing and osteophytes is consistent with osteoarthritis. However, primary osteoarthritis does not typically involve the metacarpophalangeal joints; if this occurs, suspicion should be raised for secondary osteoarthritis. Similarly, radiographs of the metacarpophalangeal joints may reveal hook-shaped osteophytes that are significantly different from radiographs of patients with primary osteoarthritis. Hemochromatosis arthropathy also may involve the proximal interphalangeal joints and, less frequently, the shoulders, hips, knees, and ankles. Finally, primary osteoarthritis usually affects patients with advanced age or who have occupations involving repetitive bending or manual labor.

Secondary osteoarthritis usually involves joints not affected by primary osteoarthritis. Secondary arthritis develops because of another condition, such as trauma, previous inflammatory arthritis, or metabolic disorders such as hemochromatosis or chondrocalcinosis. In this patient, the presence of skin hyperpigmentation and diabetes mellitus raises strong suspicion for hemochromatosis, which is particularly associated with involvement of the metacarpophalangeal joints in patients without primary osteoarthritis.

Symptoms of osteoarthritis that involve the second and third metacarpophalangeal joints also may be caused by calcium pyrophosphate deposition disease. However, radiographs of patients with this condition would typically reveal chondrocalcinosis, which occurs most frequently in the knees, symphysis pubis, and triangular fibrocartilage of the wrist.

Diabetic cheiroarthropathy (stiff hand syndrome) more commonly occurs in patients with long-standing diabetes. This condition manifests as joint stiffness, limited range of motion in the absence of pain, and skin thickening of the fingers, which is not compatible with this patient’s presentation or radiographic findings.

Rheumatoid arthritis may involve the metacarpophalangeal joints in a symmetric pattern and may be present in patients without rheumatoid factor. This condition also may manifest as rheumatoid nodules (subcutaneous nodules that develop over bony prominences at sites such as the extensor surfaces of the hand) that may resemble the bony enlargement associated with osteoarthritis. However, rheumatoid arthritis is unlikely in the absence of morning stiffness and joint swelling.

Key Point

• Secondary osteoarthritis usually involves joints not affected by primary osteoarthritis and develops because of another condition, such as trauma, previous inflammatory arthritis, or metabolic disorders such as hemochromatosis or chondrocalcinosis.

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