DC 5025Musculoskeletal SystemLast verified: APR 22, 2026

Secondary Conditions for Fibromyalgia (fibrositis, primary fibromyalgia syndrome)

Fibromyalgia (fibrositis, primary fibromyalgia syndrome) is a service-connected condition that can cause or aggravate 5 additional disabilities under 38 CFR § 3.310. Common secondaries include Chronic Fatigue Syndrome, Irritable Bowel Syndrome (Fibromyalgia-Associated), Major Depression (Fibromyalgia-Associated). Each secondary requires medical nexus evidence linking it to the primary, documented in treatment records or a private nexus letter.

“Disability which is proximately due to or the result of a service-connected disease or injury shall be service connected.”
— 38 CFR § 3.310(a), Disabilities that are proximately due to, or aggravated by, service-connected disease or injury
Evidence Strength:STRONGMODERATEEMERGING

Which secondary conditions are most common after Fibromyalgia (fibrositis, primary fibromyalgia syndrome)?

STRONG

Medical Rationale

Fibromyalgia and chronic fatigue syndrome share overlapping central sensitization pathways and co-occur in 35-70% of cases. The central nervous system amplification of sensory input in fibromyalgia extends beyond pain to produce pathological fatigue through several mechanisms: chronic microglial activation in the brainstem reticular formation disrupts arousal pathways, elevated substance P and glutamate in cerebrospinal fluid produce excitotoxic neuronal stress that depletes ATP, and non-restorative sleep from alpha-wave intrusion into delta sleep prevents normal physical recovery. The overlapping inflammatory cytokine profiles (elevated IL-1, IL-6, TNF-alpha) suggest a shared neuroimmune mechanism. The two conditions are rated separately under distinct diagnostic codes.

Key Studies

Aaron LA et al. (2000) Arch Intern Med (fibromyalgia and CFS overlap); Clauw DJ (2014) JAMA (fibromyalgia central sensitization); Naschitz JE et al. (2008) Autoimmun Rev (shared pathophysiology).

Filing Tips

Document persistent fatigue lasting >6 months not explained by other causes. Rheumatology or internal medicine records diagnosing CFS/ME with fibromyalgia as the inciting condition. Fatigue severity rating scales (FSS, Chalder Fatigue Scale). Rheumatology nexus letter addressing the shared central sensitization mechanism. VA rates CFS under DC 6354 separately from fibromyalgia (DC 5025) — document how fatigue impacts occupational functioning independently of pain.

STRONG

Medical Rationale

Fibromyalgia produces IBS through visceral hyperalgesia — the same central sensitization that amplifies somatic pain also amplifies visceral pain signaling from the gut-brain axis. The dorsal horn wind-up and reduced descending inhibition in fibromyalgia lower the pain threshold for normal gut distension and peristalsis, producing the abdominal pain, bloating, and altered bowel habits of IBS. Additionally, the autonomic dysregulation in fibromyalgia (predominantly sympathetic hyperactivity) disrupts gut motility and secretion. Elevated mast cell counts in the colonic mucosa of fibromyalgia patients release histamine and serotonin that further sensitize visceral afferents. Studies show IBS prevalence of 32-70% in fibromyalgia patients versus 8-12% in the general population.

Key Studies

Sperber AD et al. (1999) Dig Dis Sci (IBS and fibromyalgia overlap — 32-70%); Barton A et al. (1999) Eur J Gastroenterol Hepatol (central sensitization in fibromyalgia and IBS); Chang L (2011) Nat Rev Gastroenterol Hepatol (visceral hyperalgesia).

Filing Tips

GI evaluation documenting IBS diagnosis with symptom onset after fibromyalgia diagnosis. Document diarrhea-predominant, constipation-predominant, or mixed IBS subtype. GI or rheumatology nexus letter addressing visceral hyperalgesia and central sensitization as the shared mechanism. Keep a bowel symptom diary for 2-4 weeks before C&P exam. VA rates IBS under DC 7319 — severe IBS with diarrhea or alternating episodes causing more or less constant abdominal distress is rated 30%.

STRONG

Medical Rationale

Fibromyalgia and major depression have a robust, bidirectional comorbid relationship rooted in shared pathophysiology. Fibromyalgia is fundamentally a central sensitization syndrome involving dysfunction of the serotonin-norepinephrine neurotransmitter systems in descending pain modulation pathways — the identical systems implicated in MDD pathophysiology. Serotonin and norepinephrine deficiency in the brainstem's descending inhibitory pathways impair both pain modulation (→ fibromyalgia) and mood regulation (→ depression) simultaneously. Studies consistently show major depression comorbidity in 30–50% of fibromyalgia patients. The chronic unrelenting pain, sleep disruption, and functional disability of fibromyalgia create powerful secondary psychological stressors that independently precipitate depressive episodes. The effectiveness of SNRIs (duloxetine, milnacipran) in treating both fibromyalgia pain and depression confirms their shared neurochemical basis.

Key Studies

Arnold LM et al. (2006) Pain (fibromyalgia and depression neurobiological overlap); Hauser W et al. (2011) Arthritis Res Ther (fibromyalgia and psychiatric comorbidity meta-analysis); Gracely RH et al. (2004) Pain (central sensitization in fibromyalgia); Clauw DJ (2014) JAMA (fibromyalgia review).

Filing Tips

Psychiatric records documenting major depression diagnosis. Rheumatology records documenting fibromyalgia diagnosis and severity. A nexus letter from your rheumatologist and/or psychiatrist addressing the shared serotonin-norepinephrine neurotransmitter dysfunction and the chronic pain burden as dual causes of depression. If fibromyalgia is service-connected (whether direct or secondary to GWI), depression can be filed as secondary to fibromyalgia.

STRONG

Medical Rationale

Fibromyalgia produces TMJ dysfunction through central sensitization affecting the masticatory system and stress-mediated bruxism. The trigeminal nucleus, which processes orofacial pain, is subject to the same central sensitization wind-up that characterizes fibromyalgia throughout the body. This lowers the pain threshold for normal TMJ function (chewing, talking, yawning). Additionally, the chronic pain and psychological stress of fibromyalgia drive nocturnal and diurnal bruxism — clenching and grinding that overloads the TMJ disc and capsule. Myofascial trigger points in the masticatory muscles (masseter, temporalis, lateral pterygoid) are nearly universal in fibromyalgia. Studies show TMJ dysfunction prevalence of 75-97% in fibromyalgia patients.

Key Studies

Plesh O et al. (1996) J Rheumatol (TMD and fibromyalgia — 75% prevalence); Hedenberg-Magnusson B et al. (1999) Acta Odontol Scand (orofacial pain in fibromyalgia); Balasubramaniam R et al. (2007) Oral Surg Oral Med Oral Pathol Oral Radiol Endod (fibromyalgia and TMD).

Filing Tips

Dental or oral surgery evaluation documenting TMJ dysfunction. Imaging showing TMJ disc displacement or degenerative changes. Document jaw pain, limited opening, clicking/popping, and headaches from TMJ dysfunction. Oral surgeon or rheumatology nexus letter addressing central sensitization of the masticatory system. VA rates TMJ under DC 9905 — limited motion of the temporomandibular articulation. Measure inter-incisal range at C&P exam.

STRONG

Medical Rationale

Chronic opioid therapy produces hypogonadotropic hypogonadism (opioid-induced androgen deficiency, OPIAD) in 50-90% of men and causes menstrual irregularities in women. Opioids suppress gonadotropin-releasing hormone (GnRH) pulsatility in the hypothalamus, reducing LH and FSH secretion from the anterior pituitary and consequently decreasing testicular testosterone production. This endocrine disruption occurs within days of initiating opioid therapy and persists throughout treatment. The resulting testosterone deficiency produces fatigue, depression, decreased libido, erectile dysfunction, muscle wasting, osteoporosis, and metabolic syndrome. The severity of hypogonadism correlates with opioid dose — morphine equivalent doses >100 mg/day produce clinically significant testosterone suppression in virtually all male patients.

Key Studies

Rubinstein AL & Carpenter DM (2014) Pain Med (opioid-induced androgen deficiency — systematic review); Bawor M et al. (2015) J Addict Med (testosterone suppression in opioid users — meta-analysis).

Filing Tips

Morning serum testosterone level (drawn before 10 AM) documenting hypogonadism (<300 ng/dL). LH and FSH levels documenting central (hypogonadotropic) etiology. Pharmacy records documenting chronic opioid use for service-connected pain condition. Endocrinology or pain medicine nexus letter addressing GnRH suppression mechanism. Document all downstream symptoms: fatigue, depression, ED, osteoporosis. Consider under DC 7523 (testis, complete atrophy) or most analogous endocrine code. Each downstream condition (ED, depression, osteoporosis) can potentially be filed as a separate secondary claim.

How do I file a secondary service connection claim?

File VA Form 21-526EZ and list the secondary condition as a new claimed disability, noting it is secondary to Fibromyalgia (fibrositis, primary fibromyalgia syndrome). Submit a nexus letter at the time of filing — the VA does not request nexus evidence on your behalf. An effective date of Intent to File (VA Form 21-0966) protects your start date for up to 12 months while you gather medical evidence.

Common Questions About Secondary Service Connection

What is a secondary service-connected condition?

A secondary service-connected condition is a disability that is proximately caused or chronically worsened by an already service-connected condition. The VA rates secondary conditions separately and combines them with the primary rating using the combined ratings table under 38 CFR § 4.25.

What legal standard applies to secondary service connection?

38 CFR § 3.310(a) governs secondary service connection. It states: "Disability which is proximately due to or the result of a service-connected disease or injury shall be service connected." Aggravation claims — where the primary condition worsens a pre-existing disability — are covered under § 3.310(b).

Which secondary conditions are most common after Fibromyalgia (fibrositis, primary fibromyalgia syndrome)?

The 5 secondary conditions documented for Fibromyalgia (fibrositis, primary fibromyalgia syndrome) vary by evidence strength. The most strongly supported include: Chronic Fatigue Syndrome, Irritable Bowel Syndrome (Fibromyalgia-Associated), Major Depression (Fibromyalgia-Associated). Evidence strength reflects the volume and quality of medical literature linking each secondary to the primary condition.

What evidence proves a secondary condition is caused by the primary?

The most reliable evidence is a private nexus letter from a treating physician or independent medical examiner that: (1) acknowledges the service-connected primary condition, (2) diagnoses the secondary condition, and (3) states to at least a 50% probability ("as likely as not") that the primary caused or aggravated the secondary. Treatment records documenting the progression are supporting evidence, not a substitute.

How does the VA rate secondary conditions?

Secondary conditions are rated under the same 38 CFR Part 4 diagnostic codes as any other condition. The VA then combines the primary and all secondary ratings using the combined ratings formula under § 4.25 — not simple addition. For example, a 50% primary and a 30% secondary combine to 65% (rounded to 70%), not 80%.

How do I file a secondary service connection claim?

File VA Form 21-526EZ and list the secondary condition as a new claimed disability, specifically noting it is secondary to your already service-connected primary condition. Submit a nexus letter and all relevant treatment records at the time of filing. If your primary claim is already decided, you can file for the secondary as a new claim at any time — the effective date will be the date of the new claim.

Can I add secondary conditions to an existing claim after it has been decided?

Yes. Secondary conditions can be added at any time as a new claim. The effective date for the secondary will generally be the date VA receives your new claim (or the date of an Intent to File, if filed within the preceding 12 months). If the secondary was improperly denied in an earlier rating decision, a Supplemental Claim or Higher-Level Review may allow an earlier effective date.

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