Is it Fibromyalgia or Osteomalacia?

How many patients have you seen with a diagnosis of fibromyalgia?  It hurts here and there, often, for no apparent reason. 

“Three things cannot be long hidden: the sun, the moon, and the truth.”  Buddha

The convenient, but minimally helpful, diagnosis of fibromyalgia literally means:

• Fibro = fibrous tissue

• Myo = muscle

• Algia = pain

Putting this simply, your patient aches in many places. Symptoms that are often described or attributed to fibromyalgia include:1

• Muscle pain, burning, twitches, tightness

• Tender or trigger points

• Fatigue

• Trouble concentrating or impaired memory (sometimes called “fibro fog”)

• Insomnia

• Depression

The symptoms are similar to other conditions that should be considered and/or tested for. These include: hypothyroidism, various arthritides, lupus, and hormonal changes.2

Neither blood tests nor imaging point directly to fibromyalgia. Instead, it’s a diagnosis of exclusion or a way for a provider to answer the question of “what’s wrong” when they don’t really know.

Diagnosis now rendered, it’s time for treatment. The medications that are recommended are from the following classes: antidepressants, antiseizure, pain relievers, muscle relaxants, and sleep aids.3

Recommendations from providers who emphasize diet and/or natural compounds may include:4

• Green vegetables; a source of magnesium as well as other minerals

• Lean protein

• Fermented foods/cultured dairy; sources of probiotics

• Omega-3 fatty acids; healthy fats to reduce inflammation

• Antioxidants; beta carotene, vitamin C, vitamin E

But is the source of these non-specific symptoms really fibromyalgia? Or could the generalized aches with the consequent poor sleep lead to depression and “fog?” Or does depression increase pain sensitivity?

Osteomalacia

Osteomalacia means literally “bad bone.” Poor quality bone is softer, due to a deficiency of calcium or, more commonly, vitamin D. In children, vitamin D deficiency causes rickets. In adults, it is called osteomalacia. Inadequate vitamin D causes bones to soften, making them ache and more prone to fracture.5

Symptoms of osteomalacia may include:6

• Vague muscle and bone aches

• Increased susceptibility to fracture

Muscle weakness

Due to the vague and non-specific symptom picture, vitamin D deficiency frequently escapes recognition, especially in the early presentation.7

The signs of vitamin D deficiency may include:5

• Hypocalcemia

• Elevated alkaline phosphatase

• Decreased bone mineral density on a DXA examination

• Low serum 25-hydroxycholecalciferol

The blood test for vitamin D is 25-hydroxycholecalciferol; the storage form. The following are the most common laboratory thresholds.8

When looking at the blood levels of non-westernized societies (e.g.  Masai tribe), it’s common to see a level of 60 ng/ml.9  Many vitamin D researchers suggest that optimal levels should be >50 ng/ml.10  These are substantially higher than the 30 ng/ml threshold reported as normal.

 Iatrogenic vitamin D deficiency

A number of drugs are known to interfere with the vitamin D metabolism.11  The following table is arranged with the greatest to least negative.

The natural compounds, kava kava and St. John’s wort, can similarly decrease vitamin D levels.11 

Interruptions in vitamin D metabolism are not trivial.  During long-term glucocorticoid therapy, 30 to 50% of patients develop osteoporosis increasing with greater dose or duration.12  Ninety one percent of HIV positive patients taking antiretrovirals who were studied had suboptimal vitamin D levels, one third having severe deficiency.13,14  Up to 50% of patients taking long term antiseizure medications will develop bone disease with fracture risk increasing two to six times higher compared with the average population.15,16

How to begin

When a patient comes to your office reporting general muscle/bone aches, weakness, sleep disturbance, or stating they have fibromyalgia, consider that it may be unrecognized vitamin D deficiency causing osteomalacia. 

The first step is to order lab tests:

•         Complete metabolic panel, (must include serum calcium, alkaline phosphatase, liver and kidney tests)

•         Vitamin D 25-hydroxycholecalciferol level    

Also consider ordering a DXA (bone density) study.

Low vitamin D, low serum calcium, high alkaline phosphatase, and low bone mineral density, is likely osteomalacia.5,6  Though bone biopsy is the most definitive test for osteomalacia,17  it is rarely done as it is too painful.  If osteomalacia is suspected, the recommendation is to just begin vitamin D treatment.

Osteomalacia vs. osteoporosis

Osteoporosis may be confused with osteomalacia. The normal human skeleton is composed of mineral components including calcium hydroxyapatite (60%), and organic material, mainly collagen protein (40%).18

In osteoporosis, bones are porous and brittle, whereas in osteomalacia, bones are soft. This difference in bone consistency is related to the mineral-to-organic material ratio. In osteoporosis, the mineral-to-collagen ratio remains in normal reference range.  With osteomalacia, the proportion of mineral composition is reduced relative to organic matrix.18

Once the presence of vitamin D deficiency is established, the question of how much to prescribe becomes primary.  In discussing vitamin D and dose, consider that there are three sources:  sunshine-skin, food, and supplements.5

Sunshine-skin contributions are limited if your patient lives and works indoors, avoids sunshine, uses sunscreen, or has dark or aged skin.  The main food sources of vitamin D include:  fish (especially wild caught salmon and herring), oysters, and liver.  If your patient does not eat these foods nor is exposed to the sun regularly, they need supplementation.5

 Here too, there is no one answer.  With known deficiency, the combined vitamin D sources of sunshine, food, and supplements should add to at least 5000 IUs (125 mcg) per day.  Because vitamin D is fat soluble, obese patients will require 2-3 times the suggested 5000 IUs.5  Another researcher suggested 7,000 IU/day/12 weeks followed with a retest.19

Vitamin D insufficiency and deficiency are widespread.20  The implications of deficiency are numerous. Osteomalacia, directly attributable to vitamin D deficiency, is often an overlooked source of aches and pains as well as muscle weakness.

Summary

• The symptoms of osteomalacia and fibromyalgia have significant overlap. 

• As there are no identifying lab or imaging tests, fibromyalgia is a diagnosis of exclusion.

• Osteomalacia can be suspected in a symptomatic patient with low serum 25-hydroxycholecalciferol, low serum calcium, and/or high alkaline phosphatase. 

• Osteomalacia can be directly attributed to vitamin D deficiency.

• Treating a known vitamin D deficiency requires relatively large doses; 5000-7000 IU/day/12 weeks followed by a retest.  If the patient is obese, the dose should be increased 2-3 fold.

An incorrect diagnosis of fibromyalgia is a missed opportunity to treat the cause of pain.  Vitamin D is not prescribed for fibromyalgia though it is required for osteomalacia.  Wrong treatment for the wrong diagnosis with a predictable outcome of no improvement.

This article is published in The American Chiropractor Magazine 2023.

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