Subacute combined degeneration of the spinal cord in a young African-American man.

To the Editor: Subacute combined degeneration (SCD) of the spinal cord arises from deficiency of cobalamin and may be induced by pernicious anemia (PA) which typically affects patients of Northern European ancestry and tends to occur in the sixth decade of life. We recently cared for a 27-year-old African-American man who presented with numbness of the fingers bilaterally and progressive gait deterioration for six months. He experienced electric-like shocks extending down the spine upon flexing his head (L'Hermitte's sign) intermittently. He was a smoker and consumed moderate amounts of alcohol. His diet was normal and contained animal products, and there was no family or personal history of gastrointestinal or neurologic disease. On examination, his tongue was beefy. His power was mildly decreased at the iliopsoas bilaterally. His reflexes were diminished at the ankles but normal elsewhere, and he had extensor plantar responses. Sensory examination revealed decreased cold sensation in the feet. Vibratory and joint position sensations were decreased in the toes. Romberg's maneuver was positive. His gait was spastic. White blood cell count was 3.1 k/[micro]L (4.0-11.0), hemoglobin 11.7 G/dL (13.5-18), mean corpuscular volume 123 FL (80-96) and his platelet count 68 K/[micro]L. (150-400). Vitamin [B.sub.12] level was 157 pg/mL (211-911). Furthermore, he had a low thyroid stimulating hormone at 0.23 [micro]IU/mL (0.35-5.50) with positive thyroid peroxidase antibodies (16.2 IU/mL) but normal T4, T3 uptake and free T4 index. Positive serum anti-intrinsic factor antibodies were found. Magnetic resonance imaging of the brain and cervical spine was normal. He was treated with a series of five 1000 [micro]g vitamin [B.sub.12] IM injections and with monthly ones thereafter. His symptoms started improving as early as three weeks into the treatment.

Studies indicate that PA may be far commoner in people of African descent than previously thought. (1) Our patient illustrates that PA may also be much more aggressive in the African-American population. He presented with overt SCD at 27 years of age. Overall, the younger groups of patients who develop the disorder are usually of African descent. (2)

An important question is whether PA in this population represents a distinct disorder, with different natural history than the one which affects people of European ancestry. It has previously been shown that not only African-Americans but also Latin-Americans are affected earlier in life and that the disease course is much more accelerated. (3) A weak association of PA in patients of European origin with HLA-B7 was observed, but no such association has been shown in patients of African descent. (4) The association of positive serum anti-intrinsic factor antibodies with anti-peroxidase thyroid antibodies in this patient may be indicative of the severity of this autoimmune syndrome. (5) This case illustrates that in the population of African descent, PA and therefore SCD of the spinal cord are not necessarily diseases of the elderly, and that they may also be much more aggressive and accelerated than the variant seen in those of European descent, factors with prognostic and therapeutic implications.

Costas Michaelides, MD, MRCP (UK)

Janice F. Wiesman, MD

Department of Neurology

Boston University Medical Center

Boston, MA

References

1. Akinyanju OO, Okany CC. Pernicious anaemia in Africans. Clin Lab Haematol 1992;14:33-40.

2. Solanki DL, Jacobson RJ, Green R, et al. Pernicious anemia in blacks. A study of 64 patients from Washington, D. C., and Johannesburg, South Africa. Am J Clin Pathol. 1981;75:96-99.

3. Carmel R. Ethnic and racial factors in cobalamin metabolism and its disorders. Semin Hematol 1999;36:88-100.

4. Carmel R, Ozturk G, Johnson CS, et al. Profiles of black and Latin-American patients having pernicious anemia. HLA antigens, lymphocytotoxic antibody, anti-parietal cell antibody serum gastrin levels, and ABO blood groups. Am J Clin Pathol 1981;75:291-296.

5. De Block CE De Leeuw IH Van Gaal LF. High prevalence of manifestations of gastric autoimmunity in parietal cell antibody-positive type 1 (insulin-dependent) diabetic patients. The Belgian Diabetes Registry. J Clin Endocrinol Metab 1999;84:4062-4067.